Glossary

Meanings of the key words/terms in Science:

This page is under development, I am working on a way to naviagte the huge number of entries.

Key word/term	Definition
Chromatography	A technique used to separate mixtures of substances (like dyes or pigments) based on their different solubilities and how far they travel on filter paper. Common in food and forensic science.
Formulation	A mixture that has been designed with specific amounts of each component to give it desired properties.
Gas chromatography	An analytical technique used to separate and identify different substances in a mixture of gases or volatile liquids. It helps determine the composition and amount of each substance.
Mobile phase	In chromatography, the solvent that moves through the stationary phase, carrying the substances being separated.
Pigment	A substance that gives colour to materials by absorbing certain wavelengths of light. In plants, chlorophyll is a key pigment for photosynthesis.
Purity	A measure of how much of a substance is made up of only one type of particle, with no other substances mixed in.
Retention time	The time a substance takes to pass through a chromatography system.
Solute	A substance that is dissolved in a solvent to form a solution (e.g., sugar in water).
Solution	A homogeneous mixture where one substance (solute) is dissolved evenly in another (solvent).
Solvent	The substance in which the solute dissolves, usually the larger amount (e.g., water in sugar water).
Stationary phase	In chromatography, the material that does not move (like paper or a solid), which helps separate the components of a mixture.
Impure	A substance that contains more than one element or compound. It is not chemically pure and may have contaminants or unwanted materials.
Pure	A substance that contains only one type of particle and no other substances mixed in.
R_f value	A number that shows how far a substance moves in chromatography compared to the distance the solvent moves. It is calculated by dividing the distance travelled by the substance by the distance travelled by the solvent.
Solvent front	The furthest point reached by the solvent in chromatography during separation of substances.
Atmosphere	The layer of gases that surrounds the Earth. It is made mostly of nitrogen (78%) and oxygen (21%), and is essential for life and weather.
Carbon cycle	The process by which carbon is recycled in the environment, involving processes like photosynthesis, respiration, decomposition, combustion, and fossil fuel formation. It ensures carbon is continuously reused.
Carbon Footprint	The total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, activity, or person. It is usually measured in tonnes of CO₂ equivalent.
Carbon Sink	A natural system that absorbs more carbon than it releases. Examples include forests, oceans, and soil, which help reduce CO₂ levels in the atmosphere.
Catalytic Converter	A device in car exhaust systems that contains catalysts (usually platinum or rhodium) to convert harmful gases like carbon monoxide and nitrogen oxides into less harmful substances like carbon dioxide and nitrogen.
Global Climate Change	A long-term change in Earth's climate, especially increased temperatures caused by human activities, such as burning fossil fuels, leading to global warming, melting ice, and extreme weather.
Combustion	A chemical reaction in which a substance reacts with oxygen, releasing heat and light (exothermic).
Evolution	The gradual change in the characteristics of a species over time, driven by natural selection. It leads to the development of new species from earlier forms.
Global Dimming	A reduction in the amount of sunlight reaching the Earth's surface, caused by pollution and tiny particles in the air that reflect sunlight back into space. It may mask the full effects of global warming.
Global Warming	The gradual increase in Earth's average temperature, mainly due to increased greenhouse gases (like carbon dioxide and methane) from human activities such as burning fossil fuels and deforestation.
Greenhouse Effect	The natural process by which greenhouse gases trap heat (infrared radiation) in Earth?s atmosphere, keeping the planet warm enough to support life.
Photosynthesis	A chemical reaction in plants that uses carbon dioxide and water to produce glucose and oxygen using light energy.
Pollution	The introduction of harmful substances or products into the environment, causing negative effects on ecosystems and human health.
Stromatolite	Rock structures formed by layers of sediment trapped by microorganisms like cyanobacteria; some of the oldest evidence of life on Earth.
Terraforming	The hypothetical process of changing a planet?s environment (like Mars) to make it habitable for humans.
Acid rain	Rainwater that is more acidic than normal, caused by sulfur dioxide (SO₂) and nitrogen oxides (NO_x) dissolving in rain. It can damage plants, aquatic life, and buildings.
Carbon monoxide	A toxic, colorless, odorless gas formed by the incomplete combustion of fuels. It can bind to haemoglobin in red blood cells, reducing oxygen transport in the body.
Greenhouse gas	A gas that contributes to the greenhouse effect by absorbing infrared radiation.
Pollutant	A substance that causes pollution by contaminating the air, water, or soil and can harm living things.
Particulate	A tiny particle, often found in air pollution. In chemistry, it refers to the particle model of matter (atoms, molecules, or ions).
Alkali Metals	A group of very reactive metals found in Group 1 of the periodic table (e.g. lithium, sodium, potassium). They react with water to form alkaline solutions and hydrogen gas.
Atom	The smallest particle of an element that still retains the properties of that element. It consists of protons, neutrons, and electrons.
Chromatography	A technique used to separate mixtures of substances (like dyes or pigments) based on their different solubilities and how far they travel on filter paper. Common in food and forensic science.
Compound	A substance made from two or more elements that are chemically bonded together. The elements cannot be separated easily by physical means.
Condenser	A piece of laboratory equipment used to cool and condense gases into liquids during processes like distillation.
Crystallisation	A separation technique used to produce solid crystals from a solution by evaporating the solvent slowly, allowing crystals to form.
Distillation	A method used to separate mixtures based on differences in boiling points. A liquid is heated until it evaporates, then cooled and condensed into a separate container.
Electron	A tiny negatively charged particle that orbits the nucleus of an atom in energy levels (shells). Electrons are involved in chemical bonding and electric current.
Electron Shell	A region around the nucleus where electrons are likely to be found. Electrons fill the lowest available shell first.
Element	A substance made up of only one type of atom. It cannot be broken down into simpler substances by chemical means. All elements are listed in the periodic table.
Filtration	The technique or method of filtering, where a mixture is passed through a filter to separate an insoluble solid from a liquid.
Formula	A way of showing the elements in a compound and the ratio of atoms using symbols and numbers.
Groups	Vertical columns in the periodic table. Elements in the same group have similar chemical properties and the same number of electrons in their outer shell.
Halogens	The elements in Group 7 of the periodic table. They are non-metals, form -1 ions, and become less reactive down the group.
Ion	An atom or molecule that has gained or lost electrons, giving it a positive or negative charge.
Isotope	Atoms of the same element that have the same number of protons but different numbers of neutrons.
Mendeleev	Dmitri Mendeleev was a Russian scientist who created the first widely accepted periodic table, organizing elements by atomic mass and properties.
Neutron	A neutral subatomic particle found in the nucleus of an atom. It has no charge and a mass similar to a proton.
Noble Gases	Elements in Group 0 of the periodic table. They are unreactive, colourless gases with full outer electron shells (e.g. helium, neon, argon).
Nuclear	Relating to the nucleus of an atom. Often used to describe reactions involving changes in an atom?s nucleus, such as nuclear fission or fusion.
Nucleon	A particle found in the nucleus of an atom - either a proton or a neutron.
Periodic Table	A table of elements arranged by increasing atomic number and recurring chemical properties. Elements in the same group have similar properties.
Periods	The horizontal rows in the periodic table. Elements in the same period have the same number of electron shells.
Pigment	A substance that gives colour to materials by absorbing certain wavelengths of light. In plants, chlorophyll is a key pigment for photosynthesis.
Plumb Pudding Model	An early atomic model proposed by J.J. Thomson where the atom is pictured as a sphere of positive charge with electrons scattered inside like "plums" in a pudding.
Proton	A positively charged particle found in the nucleus of an atom.
Solute	A substance that is dissolved in a solvent to form a solution (e.g., sugar in water).
Solution	A homogeneous mixture where one substance (solute) is dissolved evenly in another (solvent).
Solvent	The substance in which the solute dissolves, usually the larger amount (e.g., water in sugar water).
Abundance	The number of organisms of a particular species in a given area. It's used in ecology to measure how common a species is.
Atomic number	The number of protons in the nucleus of an atom. It defines the element and determines its position in the periodic table.
Aqueous	A term used to describe a solution where the solvent is water. It is often written as (aq) in chemical equations.
Energy level	A region around the nucleus of an atom where electrons are found. Electrons occupy these levels in order, starting from the lowest energy level.
Nucleus	The central part of an atom containing protons and neutrons.
Orbit	The curved path an object takes around a planet, star, or moon due to gravity - for example, the Earth orbits the Sun.
Product	A substance formed as a result of a chemical reaction.
Reactant	A substance that starts a chemical reaction and is changed during the reaction.
Relative atomic mass	The average mass of an atom of an element compared to 1/12th of the mass of a carbon-12 atom.
Relative charge	The charge of a particle compared to the charge of a proton, which is +1.
Relative mass	The mass of a particle or atom compared to a standard, usually the carbon-12 atom.
Shell	The outer energy levels (electron shells) where electrons orbit the nucleus of an atom.
Inert	Chemically unreactive.
Chemical properties	Characteristics that describe how a substance reacts with other substances, e.g., flammability, acidity, or reactivity with water or oxygen.
Displacement	A reaction where a more reactive element replaces a less reactive one in a compound.
Group	Vertical columns in the periodic table. Elements in the same group have similar chemical properties and the same number of electrons in their outer shell.
Period	A horizontal row in the periodic table. Elements in the same period have the same number of electron shells.
Organised	In science, often refers to how structures or processes are arranged efficiently or systematically ? for example, cells being organised into tissues, organs, and systems.
Reactive	A substance that easily undergoes a chemical reaction.
Reactivity	How easily a substance reacts with other substances.
Unreactive	Describes elements or substances that do not easily take part in chemical reactions (e.g., noble gases).
Minerals	Essential chemical elements (like iron and calcium) needed in small amounts for healthy body function.
Aerobic	Describes a process that requires oxygen. For example, aerobic respiration is the release of energy from glucose using oxygen.
Anaerobic	Describes a process that does not require oxygen. For example, anaerobic respiration happens when cells release energy without using oxygen.
Cellulose	A complex carbohydrate (polysaccharide) made of glucose, found in plant cell walls. It provides strength and rigidity.
Chloroplast	A cell organelle found in plant and algal cells where photosynthesis takes place. It contains chlorophyll, which captures light energy.
Hydroponics	A method of growing plants without soil, using mineral nutrient solutions in water. Often used in greenhouses or areas with poor soil.
Inverse Square Law	A law stating that the intensity of a force or radiation is inversely proportional to the square of the distance from the source.
Lactic acid	A substance produced in muscles during anaerobic respiration when oxygen is limited; causes muscle fatigue.
Limiting Factor	A condition or resource that restricts the rate of a biological process, such as light, temperature, or carbon dioxide in photosynthesis.
Metabolism	The sum of all chemical reactions in the body, including those that break down nutrients and those that build new materials.
Muscle fatigue	When muscles get tired and cannot contract efficiently, usually due to a build-up of lactic acid from anaerobic respiration.
Photosynthesis	The process by which green plants use light energy to convert carbon dioxide and water into glucose and oxygen:
Respiration	A chemical process in cells where glucose is broken down with oxygen to release energy.
Starch	A carbohydrate used by plants to store energy; it is made of many glucose units linked together.
Chlorophyll	A green pigment found in chloroplasts of plant cells. It absorbs light energy needed for photosynthesis.
Carbon dioxide	A colorless gas produced by respiration, combustion, and other processes. It is used by plants in photosynthesis and is a greenhouse gas.
Concentration	The amount of a substance (solute) dissolved in a certain volume of solvent or solution.
Endothermic	A reaction that takes in energy from the surroundings, usually as heat, causing the surroundings to cool down.
Glucose	A simple sugar that is an important source of energy for cells. Its formula is C₆H₁₂O₆. Glucose is produced in photosynthesis and broken down in respiration.
Greenhouse gases	The group of gases in the atmosphere that trap heat and contribute to global warming. These include CO₂, CH₄, N₂O, and water vapour.
Light intensity	The amount of light per unit area; in biology, it affects the rate of photosynthesis in plants.
Amino acid	A small molecule that is the building block of proteins. There are 20 different types of amino acids, and they link together in chains to form proteins, following the instructions in DNA.
Carbohydrate	A macronutrient made of carbon, hydrogen, and oxygen. It provides energy to the body. Examples include sugars and starches.
Exothermic	A chemical reaction that releases energy to the surroundings, usually in the form of heat, making the surroundings warmer.
Fermentation	A process by which microorganisms (like yeast) break down sugars anaerobically (without oxygen) to produce substances like ethanol and carbon dioxide.
Fatty acid	A long hydrocarbon chain with a carboxylic acid group, found in lipids (fats and oils). Fatty acids combine with glycerol to form triglycerides.
Glycerol	A small molecule that combines with fatty acids to form lipids (fats and oils). It is part of the structure of triglycerides.
Glycogen	A storage form of glucose found in animal cells, especially in the liver and muscles. It can be broken down into glucose when energy is needed.
Lipid	A type of biological molecule that includes fats and oils; used for energy storage, insulation, and making cell membranes.
Mitochondria	Structures in cells where respiration occurs; they release energy from glucose (often called the "powerhouse" of the cell).
Oxidation	The process in which glucose is broken down with oxygen during aerobic respiration to release energy.
Oxygen debt	The extra oxygen the body needs after exercise to break down lactic acid and repay the temporary lack of oxygen during anaerobic respiration.
Protein	Large molecules made of amino acids that perform many important functions in the body, such as building cells and enzymes.
Allotrope	Different forms of the same element in the same physical state with different structures and properties (e.g. diamond and graphite are allotropes of carbon).
Alloy	A mixture of a metal with one or more other elements, usually to improve its properties (e.g. strength, resistance to corrosion). Example: steel is an alloy of iron and carbon.
Charges	Particles or objects that carry positive or negative electrical charge. Opposite charges attract, and like charges repel.
Conductivity	A measure of how well a material conducts electricity or heat. Metals have high conductivity, while non-metals often have low conductivity.
Covalent	A chemical bond formed when two non-metal atoms share electrons to achieve full outer shells. Covalent bonds are strong and found in molecules like H?O and CO?.
Delocalised electrons	Electrons that are not associated with a single atom or bond. In metals, they are free to move, allowing electricity and heat to conduct. In benzene, delocalised electrons are shared in a ring structure.
Diamond	A form (allotrope) of carbon where each carbon atom is bonded to four others in a giant covalent structure. It is very hard, has a high melting point, and does not conduct electricity.
Electrostatic Attraction	The non-contact force between oppositely charged particles, such as positive ions and negative electrons. It's responsible for ionic bonding and effects like static electricity.
Free Moving Ions	Charged particles that are free to move, allowing electric current to flow. Found in molten or dissolved ionic compounds, and in electrolytes.
Fullerene	A form of carbon where atoms are arranged in hollow spheres, tubes, or cages (e.g., buckyballs or nanotubes). They have high strength and unique properties used in nanotechnology and electronics.
Graphene	A single layer of carbon atoms arranged in a hexagonal (honeycomb) structure. It is very strong, light, and an excellent conductor of heat and electricity.
Graphite	A form of carbon made of layers of graphene. The layers can slide over each other, making graphite slippery and useful as a lubricant or in pencils. It also conducts electricity.
Intermolecular Forces	Weak forces of attraction between molecules.
Ion	An atom or molecule that has gained or lost electrons, giving it a positive or negative charge.
Lattice	A regular, repeating arrangement of atoms, ions, or molecules in a solid; common in ionic compounds and metals.
Nanoparticles	Very small particles (1?100 nanometres in size) with a high surface area to volume ratio; used in medicine, electronics, and cosmetics.
Polymers	Large molecules made by joining many small molecules called monomers together.
Simple Molecules	Small molecules made of a few atoms bonded together, usually with low melting and boiling points (e.g., water, carbon dioxide).
Sublimation	The change of state from a solid directly to a gas (or gas to solid) without passing through the liquid state (e.g., dry ice).
Conductor	A material that allows heat or electricity to pass through it easily. Examples: copper, aluminium.
Malleable	A property of metals that allows them to be hammered or bent into shape without breaking.
Transfer	The movement of something from one place to another?often used in energy transfer, or transferring electrons during chemical reactions.
Surface area to volume ratio	The ratio of surface area to volume. Smaller objects have a higher surface area to volume ratio, which can affect processes like diffusion and reaction rates.
Active transport	The movement of substances against a concentration gradient (from low to high concentration) using energy from respiration. It happens across cell membranes.
Chloroplast	A cell organelle found in plant and algal cells where photosynthesis takes place. It contains chlorophyll, which captures light energy.
Chromosome	Thread-like structures found in the nucleus of cells. They are made of DNA and carry genes. Humans have 46 chromosomes (23 pairs).
Concentration	The amount of a substance (solute) dissolved in a certain volume of solvent or solution.
Cytoplasm	The jelly-like substance inside cells where most chemical reactions occur. It contains enzymes and organelles.
Differentiate	When a cell becomes specialised to perform a specific function. For example, a stem cell can differentiate into a nerve cell or muscle cell.
Diffusion	The net movement of particles from an area of higher concentration to lower concentration, down a concentration gradient. It is a passive process (no energy required).
Diffusion	The net movement of particles from an area of higher concentration to lower concentration, down a concentration gradient. It is a passive process (no energy required).
Embryonic	Relating to an embryo ? the early stages of development in animals or humans.
Eukaryote/eukaryotic	A type of cell that has a nucleus and membrane-bound organelles. Found in plants, animals, fungi, and protists.
Flagella	Tail-like structures that allow bacteria or sperm cells to move. They spin like a propeller to enable swimming.
Magnification	How much larger an image is compared to the actual object; calculated by image size ? actual size.
Cell membrane	The thin outer layer of a cell that controls what enters and leaves the cell. It is partially permeable.
Mitochondria	Structures in cells where respiration occurs; they release energy from glucose (often called the "powerhouse" of the cell).
Mitosis	A type of cell division that produces two genetically identical daughter cells for growth and repair.
Nucleus	The part of a cell that contains genetic material (DNA) and controls cell activities.
Osmosis	The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
Osmosis	The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
Prokaryote/prokaryotic	A simple type of cell without a nucleus, found in bacteria.
Resolution	The ability of a microscope or other instrument to distinguish between two points that are close together.
Surface Area to Volume Ratio	The comparison of the surface area of an object (like a cell) to its volume. A higher ratio allows faster exchange of substances like gases or nutrients.
Turgid	Describes a plant cell that is full of water, making it swollen and firm due to water pressure inside the vacuole.
Permanent vacuole	A large structure found in plant cells that contains cell sap and helps maintain cell structure and pressure.
Cell wall	A rigid outer layer found in plant, fungal, and bacterial cells that provides structure and support. In plants, it is made of cellulose.
Dilute	A solution that has a small amount of solute compared to solvent. For example, dilute acid has less acid per unit of water.
DNA	A large molecule that carries the genetic instructions for the development and function of living organisms.
Gill filaments	Thin structures in fish gills that provide a large surface area for gas exchange, allowing oxygen to enter the blood and carbon dioxide to leave.
Gradient	A difference in concentration, pressure, or temperature between two areas.
Partially permeable membrane	A membrane that allows only certain small molecules (like water) to pass through while blocking larger molecules - crucial for osmosis.
Passive process	A biological process that does not require energy (ATP), e.g. diffusion or osmosis.
Plasmid	A small, circular piece of DNA found in bacteria that can replicate independently and often carries genes that provide advantages, such as antibiotic resistance.
Resolution	The ability of a microscope or other instrument to distinguish between two points that are close together.
Ribosome	A tiny structure in cells where proteins are made.
Root hair cell	A plant cell with a long extension (root hair) that increases surface area for absorbing water and minerals from the soil.
Stomata	Tiny pores on the surface of leaves that allow gases (like carbon dioxide and oxygen) to enter and leave the plant.
Adult stem cell	A type of stem cell found in adult tissues (like bone marrow) that can differentiate into a limited range of cells (e.g., blood cells), used in medicine to treat some diseases.
Binary fission	A form of asexual reproduction used by bacteria, where a single cell splits into two identical cells. It can happen very quickly under the right conditions.
Cell cycle	The series of stages that a cell goes through to grow and divide, including growth, DNA replication, and mitosis.
Clone	An organism or cell that is genetically identical to the one from which it was produced. Cloning can occur naturally (e.g., identical twins) or artificially (e.g., in the lab or by cuttings in plants).
Daughter cells	The two new cells formed after cell division (such as mitosis). In mitosis, daughter cells are genetically identical to the parent cell.
Embryonic stem cell	A type of stem cell found in embryos that can differentiate into any type of cell in the body. Used in medical research and treatments.
Gene	A section of DNA that codes for a specific protein. Genes determine inherited characteristics.
Meristem	A region in plants (usually at the tips of roots and shoots) where cells divide rapidly for growth.
Therapeutic cloning	A process where an embryo is created using a person's DNA to produce stem cells that could be used to treat disease without being rejected by the body.
Acid	A substance with a pH less than 7 that produces hydrogen ions (H⁺) in solution. Acids have sour taste and can react with metals, bases, and carbonates.
Alkali	A base that is soluble in water and forms hydroxide ions (OH^-) in solution. Alkalis have a pH greater than 7 and can neutralise acids.
Aqueous	A term used to describe a solution where the solvent is water. It is often written as (aq) in chemical equations.
Base	A substance that reacts with acids to form salt and water. Soluble bases are called alkalis, and bases have a pH greater than 7.
Bauxite	The main ore of aluminium. It contains aluminium oxide, which is extracted by electrolysis to produce pure aluminium metal.
Cryolite	A substance used in the electrolysis of aluminium oxide. It lowers the melting point of aluminium oxide, making the process cheaper and more efficient.
Displacement	A reaction where a more reactive element replaces a less reactive one in a compound.
Dissociation	The process where a compound splits into ions in a solution. For example, acids dissociate in water to release H? ions.
Electrolysis	A process that uses electricity to break down an ionic compound into its elements. It requires a liquid (molten or in solution) electrolyte and two electrodes.
Electrolyte	An ionic compound in molten form or solution that can conduct electricity and is broken down during electrolysis.
Native	Refers to a species that naturally occurs in a particular region or environment without human introduction.
Neutralisation	A chemical reaction in which an acid and a base react to form a salt and water, cancelling each other out.
Ore	A rock that contains enough of a metal or mineral to make it economically worthwhile to extract.
Oxidation	A reaction where a substance gains oxygen or loses electrons.
Reactivity	How easily a substance reacts with other substances.
REDOX	A chemical reaction involving both reduction (gain of electrons) and oxidation (loss of electrons).
Reduction	The gain of electrons by a substance in a chemical reaction.
Extraction	The process of removing a metal from its ore. Methods include electrolysis, reduction with carbon, or displacement reactions.
Half equation	An equation showing either the oxidation or reduction part of a redox reaction, usually in electrolysis.
Ion	An atom or molecule that has gained or lost electrons, giving it a positive or negative charge.
Ionic equation	A simplified chemical equation that shows only the ions and molecules directly involved in a chemical reaction, excluding spectator ions.
Reactivity series	A list of metals arranged in order of how easily they react, from most reactive to least reactive.
Spectator ion	An ion that does not take part in a chemical reaction and remains unchanged in solution.
State symbols	Symbols used in chemical equations to show the physical state of substances
Anode	The positive electrode in electrolysis. It is where negative ions lose electrons (are oxidised).
Cathode	The negative electrode in electrolysis, where reduction (gain of electrons) takes place. Positively charged ions are attracted to it.
Abiotic Factors	Non-living parts of an environment that affect organisms, such as temperature, light intensity, pH, moisture levels, and wind.
Adaptation	A feature or characteristic that helps an organism survive and reproduce in its environment. Adaptations can be structural, behavioural, or functional.
Biodiversity	The variety of different species of plants, animals, and microorganisms living in an ecosystem or on Earth as a whole. High biodiversity helps ecosystems stay stable and resilient.
Biotic Factors	Living factors in an ecosystem that affect organisms, such as predators, food availability, competition, and disease.
Carbon Cycle	The process by which carbon is recycled in the environment, involving processes like photosynthesis, respiration, decomposition, combustion, and fossil fuel formation. It ensures carbon is continuously reused.
Communities	All the different populations of organisms living and interacting in a particular habitat at the same time.
Competition	When organisms compete for the same resources (such as food, light, water, or mates) in an ecosystem. It can occur within or between species.
Cycling of Materials	The movement and recycling of elements (e.g. carbon, nitrogen) through living organisms and the environment, ensuring materials are reused in ecosystems.
Deforestation	The removal of large areas of trees or forests, often for agriculture or development. It can lead to loss of biodiversity, soil erosion, and increased carbon dioxide levels.
Detritus	Dead organic matter, such as dead plants, animals, and waste, that is broken down by decomposers in ecosystems.
Ecosystem	A community of living organisms (biotic) interacting with the non-living environment (abiotic) in a particular area. Includes relationships like predation, competition, and nutrient cycling.
Global Warming	The gradual increase in Earth's average temperature, mainly due to increased greenhouse gases (like carbon dioxide and methane) from human activities such as burning fossil fuels and deforestation.
Habitat	The natural environment where an organism lives and interacts with other organisms and its surroundings.
Interdependence	The reliance of organisms on one another for resources like food, shelter, and pollination. It helps maintain stability in an ecosystem.
Migration	The seasonal movement of animals from one region to another, often to find food, breed, or avoid harsh conditions.
Quadrat	A square frame used to count and study plants or animals in a specific area to estimate population size.
Recycling	The process of converting waste materials into new materials to reduce waste and save resources.
Resources	Materials or substances that organisms need to live and grow, such as water, nutrients, and space.
Transect	A straight line or narrow area through a habitat along which ecological measurements (like species distribution) are taken.
Peat bog	Waterlogged areas of land where dead plant material accumulates and decays very slowly; important carbon stores and habitats.
Pollution	The presence of harmful substances in the environment, such as chemicals or waste, which can damage living organisms and ecosystems.
Biomass	Biological material from living or recently living organisms (e.g. wood, crops, or manure) used as a source of energy.
Carnivore	An animal that eats only other animals. Carnivores are consumers and may be secondary or tertiary consumers in a food chain.
Consumer	An organism that gets its energy by eating other organisms. Consumers can be primary (herbivores), secondary, or tertiary.
Decomposer	An organism, such as bacteria or fungi, that breaks down dead plants and animals, returning nutrients to the environment and helping in the cycling of materials.
Evaporation	The process by which particles at the surface of a liquid gain energy and turn into a gas. It causes cooling as energy is taken from the surroundings.
Fertiliser	A substance added to soil to supply essential nutrients (like nitrogen, phosphorus, and potassium) to help plants grow.
Food chain	A sequence of organisms showing how energy and nutrients flow through an ecosystem, starting from a producer and moving to consumers.
Food web	A network of interconnected food chains showing how different organisms are linked in an ecosystem through feeding relationships.
Herbivore	An animal that only eats plants. Herbivores are primary consumers in a food chain.
Precipitation	Water falling from clouds to the Earth?s surface, including rain, snow, sleet, or hail.
Predator	An animal that hunts, kills, and eats other animals.
Prey	An animal that is hunted and eaten by a predator.
Producer	An organism, like a plant, that makes its own food using sunlight through photosynthesis.
Trophic level	A step in a food chain or food web, representing an organism's position in the flow of energy (e.g., producer, primary consumer).
Water cycle	The continuous movement of water through the environment, involving processes like evaporation, condensation, precipitation, and transpiration.
Extremophile	A microorganism that lives in extreme conditions, such as high temperature, pressure, or acidity, like those found in deep-sea vents or hot springs.
Interaction	The way in which two or more things affect each other.
Interspecific competition	When individuals of different species compete for the same resources (like food, space, or water) in an ecosystem.
Intraspecific competition	When individuals of the same species compete for resources such as mates, food, and territory.
Direct Current	A type of electric current where the flow of charge is in one direction only. It is supplied by batteries and cells.
Ohmic Conductor	A conductor that obeys Ohm?s Law, meaning the current through it is directly proportional to the voltage across it, provided the temperature remains constant (e.g. a resistor).
Parallel Circuit	A circuit in which components are connected on separate branches. The current splits and each component receives the same voltage.
Potential Difference	The difference in electric potential energy between two points in a circuit; it causes current to flow.
Residual Current Circuit Breaker (RCCB)	A safety device that quickly switches off the electricity supply if it detects a current leak to prevent electric shocks.
Resistance	A measure of how much a component or material reduces the flow of electric current, measured in ohms (Ω).
Series Circuit	An electric circuit where components are connected one after another, so there is only one path for current to flow.
Thermistor	A temperature-sensitive resistor. Its resistance decreases as temperature increases (used in temperature sensors).
Transformer	A device that changes the voltage of alternating current (AC), using electromagnetic induction. It can step voltage up or down for efficient power transmission.
Voltage	The energy transferred per unit charge in a circuit. It is measured in volts (V).
Fuse	A safety device in an electrical circuit that contains a thin wire which melts and breaks the circuit if the current is too high, preventing damage or fire.
Alternating potential difference	A potential difference (voltage) that changes direction and size repeatedly over time. It is associated with alternating current and can be represented as a waveform, usually a sine wave.
Charge flow	The amount of electric charge that passes a point in a circuit. It is measured in coulombs (C)
Coulombs	The unit of electric charge. One coulomb is the amount of charge that passes when a current of 1 amp flows for 1 second.
National grid	A network of cables and transformers that distributes electricity from power stations to homes and businesses across the country.
Short circuit	A fault in an electric circuit where current flows along an unintended path with little or no resistance, often causing overheating or damage.
Direct potential difference	The voltage in a circuit where current flows in one direction only, supplied by sources like batteries. It causes a steady (DC) flow of electric charge.
Step-up transformer	A transformer that increases voltage while decreasing current, used in power lines to transmit electricity efficiently over long distances.
Step-down transformer	A transformer that decreases voltage while increasing current, often used in devices for home use.
Ampere	The unit of electric current. One ampere is equal to a flow of one coulomb of charge per second.
Electrostatic force	The non-contact force between oppositely charged particles, such as positive ions and negative electrons. It's responsible for ionic bonding and effects like static electricity.
Light dependent resistor (LDR)	A resistor whose resistance decreases as light intensity increases; used in devices like automatic lights.
Alternating Current	An electric current that reverses direction regularly. In the UK, mains electricity is AC with a frequency of 50 Hz, meaning it changes direction 50 times per second.
Charge	A property of particles (like protons and electrons) that causes them to attract or repel each other. Protons are positively charged, electrons are negatively charged, and neutrons have no charge.
Current	The flow of electric charge (electrons) around a circuit. It is measured in amperes (A) using an ammeter.
Diode	An electronic component that allows current to flow in one direction only. It is used for rectifying alternating current to direct current.
Closed System	A system where no matter can enter or leave, but energy can be transferred. In chemistry and physics, it means the mass stays constant, even if energy changes.
Conduction	The transfer of thermal or electrical energy through a substance, without movement of the substance itself. In solids, energy is transferred by vibrating particles or free electrons.
Conservation of Energy	A law stating that energy cannot be created or destroyed?it can only be transferred, stored, or transformed from one form to another. The total energy in a closed system remains constant.
Convection	The transfer of thermal energy through fluids (liquids or gases) caused by movement of particles. Hot fluids rise and cooler ones sink, creating convection currents.
Efficiency	A measure of how much useful energy output you get from a system compared to the total energy input.
Elastic Potential	The energy stored in an object when it is stretched or compressed, such as in a spring or elastic band.
Electrostatic Attraction	The non-contact force between oppositely charged particles, such as positive ions and negative electrons. It's responsible for ionic bonding and effects like static electricity.
Geothermal	Renewable energy from the heat inside the Earth. It is used to generate electricity or heat buildings using hot rocks or steam underground.
Gravitational Potential	The potential energy an object has due to its position in a gravitational field.
Hydroelectric	Electricity generated by water, typically using flowing or falling water to turn turbines in a dam or river system.
Kinetic	Related to movement. In science, it often refers to kinetic energy, which is the energy an object has because of its motion.
Potential	A chemical reaction where a solid forms and separates out from a solution.
Specific Heat Capacity	The energy required to raise the temperature of 1 kg of a substance by 1°C.
Thermal Radiation	The transfer of energy by infrared (IR) waves. All objects emit thermal radiation depending on their temperature.
Work Done	The energy transferred when a force moves an object over a distance.
Absorb	To take in or soak up energy, substances, or materials. For example, plants absorb light for photosynthesis, and black surfaces absorb heat.
Thermal conductivity	A measure of how well a material transfers heat. Materials with high thermal conductivity (like metals) transfer heat quickly.
Thermal insulator	A material that does not conduct heat well and is used to reduce heat transfer (e.g., wool, foam, plastic).
Chemical energy	A form of potential energy stored in chemical bonds. It is released or absorbed during chemical reactions, such as combustion or respiration.
Dissipated	When energy is spread out and becomes less useful, often transferred to the surroundings as thermal energy (heat). Dissipated energy cannot be used for work.
Lubrication	The application of a substance (like oil or grease) to reduce friction between two surfaces in contact.
Magnetic	Describes materials (like iron, nickel, and cobalt) that are attracted to a magnet or can be magnetised.
Nuclear	Relating to the nucleus of an atom. Often used to describe reactions involving changes in an atom?s nucleus, such as nuclear fission or fusion.
Power	The rate at which energy is transferred or work is done, measured in watts (W).
Streamlining	Designing an object so air or fluid flows smoothly around it, reducing drag or resistance.
System	A group of interacting parts or components that can be studied together, often in terms of energy transfer (e.g. a closed or open system).
Thermal	Related to heat or temperature. Often used in terms like ?thermal energy? or ?thermal transfer?.
Biofuel	A renewable fuel made from biological material, such as plants (e.g. sugarcane, maize) or animal waste, used as an alternative to fossil fuels.
Carbon neutral	When the amount of carbon dioxide released into the atmosphere is balanced by actions that remove or offset an equivalent amount (e.g. planting trees or using carbon credits).
Environmental impact	The effect of an activity (especially human) on the natural environment, such as pollution, deforestation, or loss of biodiversity.
Fossil fuel	A non-renewable energy source formed from the remains of dead plants and animals over millions of years.
Renewable	A resource or energy source that can be replenished naturally over a short time period.
Non-renewable	A resource that cannot be replaced within a human timescale once it is used, e.g. fossil fuels like coal, oil, and gas.
Reliability	How consistently a measurement or experiment produces the same results under the same conditions.
Activation Energy	The minimum amount of energy needed for a chemical reaction to start. Enzymes lower the activation energy required.
Bond Energy	The amount of energy needed to break one mole of a specific type of bond in a molecule in the gas phase. It is measured in kJ/mol and helps calculate energy changes in reactions.
Endothermic	A reaction that takes in energy from the surroundings, usually as heat, causing the surroundings to cool down.
Exothermic	A chemical reaction that releases energy to the surroundings, usually in the form of heat, making the surroundings warmer.
Reaction Profile	A graph showing the energy changes during a chemical reaction, including the activation energy and whether the reaction is exothermic or endothermic.
Specific Heat Capacity	The amount of energy needed to raise the temperature of 1 kilogram of a substance by 1 degree Celsius.
Combustion	A chemical reaction in which a substance reacts with oxygen, releasing heat and light (exothermic).
Neutralisation	A chemical reaction in which an acid and a base react to form a salt and water, cancelling each other out.
Oxidation	A reaction where a substance gains oxygen or loses electrons.
Thermal decomposition	A chemical reaction where a substance breaks down into simpler substances when heated (e.g., calcium carbonate → calcium oxide + carbon dioxide).
Acceleration	The rate of change of velocity of an object. It is measured in metres per second squared (m/s²) and can involve speeding up, slowing down, or changing direction.
Conservation of Momentum	In a closed system, the total momentum before an event (like a collision) is equal to the total momentum after the event, provided no external forces act.
Displacement (distance)	The shortest distance between two points in a straight line, along with a direction. It differs from distance, which measures the total path taken.
Elastic Deformation	Temporary deformation ? when a material is stretched and returns to its original shape once the force is removed.
Equilibrium	In a reversible reaction, equilibrium is reached when the forward and reverse reactions happen at the same rate, and the concentrations of reactants and products stay constant.
Gravitational	Relating to gravity, the force of attraction between masses. It pulls objects toward each other, like Earth pulling objects downward.
Limit of Proportionality	The point beyond which a material no longer obeys Hooke?s Law, meaning the extension is no longer proportional to the force applied.
Momentum	A measure of the motion of an object
Resultant force	The overall force acting on an object when all the forces are combined.
Scalar	A quantity that has only magnitude (size) and no direction, like temperature or speed.
Terminal Velocity	The constant speed that a falling object reaches when the force of air resistance balances the force of gravity, so it no longer accelerates.
Vector	A quantity that has both magnitude and direction, such as force, velocity, or acceleration.
Velocity	The speed of an object in a given direction (a vector quantity, unlike speed, which is scalar).
Centro of mass	The point in an object where its mass is evenly distributed and gravity appears to act. An object will balance at its centre of mass.
Gravitational field strength	The force of gravity on 1 kg of mass.
Inertia	The tendency of an object to resist a change in motion. An object at rest stays at rest, and an object in motion stays in motion unless acted on by a force.
Inertial mass	A measure of how difficult it is to change the velocity of an object.
Newton's second law	States that the force acting on an object is equal to its mass times its acceleration:
Recoil	The backward movement of an object when it pushes another object forward (like the kickback of a gun when fired).
Weight	The force acting on an object due to gravity.
Braking distance	The distance a vehicle travels after the brakes are applied until it comes to a complete stop. It is affected by speed, road conditions, and the condition of the brakes and tyres.
Deceleration	A decrease in speed (negative acceleration). It occurs when an object slows down.
Deformation	A change in shape of an object due to a force being applied. It can be elastic (temporary) or inelastic (permanent).
Elastic	A material is elastic if it returns to its original shape after being stretched or compressed (as long as it doesn't exceed the elastic limit).
Inelastic	A type of collision or material where energy is not conserved as kinetic energy. In inelastic collisions, some energy is converted into heat or sound, and objects may not bounce back.
Reaction time	The time taken for a person or system to respond to a stimulus.
Stopping distance	The total distance a vehicle travels from the moment the driver spots a hazard to when the vehicle stops. It is the sum of the thinking distance and braking distance.
Thinking distance	The distance a vehicle travels in the time it takes a driver to react to a hazard before applying the brakes.
Adrenaline	A hormone released by the adrenal glands in response to stress or danger. It increases heart rate, boosts blood flow to muscles, and raises blood sugar levels for energy.
Central Nervous System	Consists of the brain and spinal cord. It processes information from the sense organs and coordinates the body?s response.
Contraception	Methods used to prevent pregnancy, including barrier methods (e.g. condoms), hormonal methods (e.g. the pill), and surgical methods.
Coordination	The way the nervous system and hormonal system work together to control and regulate body functions, ensuring appropriate responses to stimuli.
Diabetes	A medical condition where the body cannot properly regulate blood glucose levels. It is caused by either not producing enough insulin (Type 1) or the body not responding to insulin (Type 2).
Effectors	Muscles or glands that respond to impulses from the nervous system by producing a response, such as moving a limb or releasing a hormone.
Endocrine system	The body system made up of glands that release hormones directly into the bloodstream to control body functions like growth, metabolism, and reproduction.
Fertility	The ability to reproduce. In humans, it refers to the capacity to conceive children.
Homeostasis	The regulation of internal conditions (like temperature, blood glucose, and water levels) to maintain a stable internal environment in the body.
Hormone	A chemical messenger produced by glands in the body that travels in the blood to target organs to regulate body processes.
In Vitro Fertilisation (IVF)	A medical procedure where an egg is fertilised by sperm outside the body, and the resulting embryo is implanted into the uterus. Used to treat infertility.
Insulin	A hormone produced by the pancreas that helps lower blood glucose levels by allowing glucose to enter cells and be stored as glycogen in the liver.
Menstrual Cycle	The monthly cycle in females where the uterus lining builds up and is shed if no fertilisation occurs; controlled by hormones like oestrogen and progesterone.
Negative Feedback	A control mechanism that counteracts changes to bring a system back to normal, e.g. in body temperature or blood glucose regulation.
Oestrogen	A female sex hormone that controls the development of female secondary sexual characteristics and regulates the menstrual cycle.
Optimum	The best or most favourable condition for a process or reaction to happen, such as the optimum temperature or pH for enzyme activity.
Progesterone	A hormone involved in the menstrual cycle and pregnancy in females.
Reaction Time	The time it takes for a person to respond to a stimulus.
Reflex Arc	The pathway taken by nerve impulses during a reflex action, typically involving a receptor, sensory neuron, relay neuron, motor neuron, and effector.
Relay Neurone	A nerve cell in the central nervous system that connects sensory neurones to motor neurones.
Sensory Neurone	A nerve cell that carries electrical impulses from sensory receptors (like skin or eyes) to the central nervous system (brain or spinal cord).
Stimulus	A change in the environment that is detected by receptors and may cause a response (e.g., light, sound, temperature).
Synapse	The tiny gap between two neurones where a chemical signal (neurotransmitter) is passed to transmit a nerve impulse.
Testosterone	The main male sex hormone, responsible for the development of male secondary sexual characteristics and the production of sperm.
Thyroxine	A hormone produced by the thyroid gland that controls the body?s metabolic rate.
Adrenal gland	A gland located above each kidney that produces hormones, including adrenaline, which helps the body respond to stress (fight or flight response).
Glucagon	A hormone produced by the pancreas that raises blood glucose levels by causing the conversion of glycogen into glucose in the liver. It works opposite to insulin.
Metabolic rate	The speed at which the body's chemical reactions (metabolism) take place, especially those that release energy from food.
Pancreas	A gland that produces digestive enzymes and the hormones insulin and glucagon to regulate blood sugar levels.
Pituitary gland	A small gland at the base of the brain often called the "master gland" because it controls other glands and releases important hormones like growth hormone and FSH.
Thyroid gland	A gland in the neck that produces hormones (like thyroxine) which regulate metabolism, heart rate, and body temperature.
Involuntary	Actions or muscles that work without conscious control.
Neurones	Nerve cells that transmit electrical impulses throughout the body. There are sensory, motor, and relay neurones.
Receptors	Special cells or nerve endings that detect changes in the environment (stimuli).
Reflex action	A quick, automatic response to a stimulus that does not involve conscious thought.
Spinal cord	The bundle of nerve fibers that runs down the backbone, transmitting messages between the brain and the rest of the body.
Follicle stimulating hormone (FSH)	A hormone released by the pituitary gland that causes egg maturation in ovaries and stimulates oestrogen production. In men, it stimulates sperm production.
Infertility	The inability to conceive a child naturally. It can affect men or women and may be treated with methods like IVF (in vitro fertilisation).
Ovary	A female reproductive organ that produces egg cells (ova) and hormones such as oestrogen and progesterone.
Luteinising hormone (LH)	A hormone produced by the pituitary gland that triggers ovulation and stimulates the production of progesterone in females.
Ovulation	The release of a mature egg from an ovary, typically around the middle of the menstrual cycle.
Testes	The male reproductive organs that produce sperm and the hormone testosterone.
Antibiotic resistance	When bacteria evolve so that antibiotics no longer kill them. This can lead to infections that are harder to treat and is a major concern in medicine.
Antibiotics	Medicines that help to kill or stop the growth of bacteria without harming human cells. They do not work on viruses.
Antibodies	Proteins produced by white blood cells (lymphocytes) that recognise and bind to specific antigens on pathogens to help destroy them.
Bacteria	Single-celled microorganisms that can be beneficial (e.g., in digestion or decomposition) or harmful (e.g., causing disease). They reproduce quickly by binary fission.
Cardiovascular	Relating to the heart and blood vessels. The cardiovascular system transports blood, oxygen, and nutrients around the body.
Communicable	A disease that can be spread from one organism to another, caused by pathogens such as bacteria, viruses, fungi, or parasites. Example: flu, measles.
Double-blind Trial	A type of clinical trial where neither the participants nor the researchers know who is receiving the active drug or the placebo. This helps remove bias and ensures reliable results.
Fungus	A kingdom of living organisms including mushrooms, yeasts, and moulds. They are decomposers, breaking down organic matter, and do not photosynthesise.
Immunity	The body?s ability to resist infection or disease by producing white blood cells or antibodies. Can be natural (from infection) or artificial (from vaccination).
Non-communicable	A type of disease that cannot be spread from person to person, such as cancer, diabetes, or heart disease.
Pathogen	A microorganism that causes disease, such as bacteria, viruses, fungi, or protists.
Phagocytosis	A process where white blood cells (phagocytes) engulf and digest pathogens or harmful particles.
Placebo	A substance with no active ingredient used in clinical trials as a control to test the effectiveness of a new drug; patients given the placebo should not experience real medical effects.
Protozoa	Single-celled, animal-like organisms found in water or soil, some of which can cause diseases.
Salmonella	A type of bacteria that causes food poisoning.
Stent	A small mesh tube inserted into arteries to keep them open and improve blood flow, often used in patients with coronary heart disease.
Vaccination	The process of injecting a weakened or inactive form of a pathogen to stimulate the immune system and provide protection against disease.
Virus	A tiny pathogen that can only reproduce inside living cells, causing diseases like flu, HIV, or measles.
Artificial heart	A mechanical device used to replace a damaged heart, either temporarily (while waiting for a transplant) or permanently. It helps pump blood around the body.
Benign	Describes a non-cancerous tumour that does not spread to other parts of the body. It can still cause problems if it grows large or presses on organs.
Carcinogen	A substance that causes cancer or increases the risk of developing it. Examples include tobacco smoke, asbestos, and UV radiation.
Cholesterol	A fatty substance found in the blood. It is needed to build cell membranes but too much (especially of the "bad" type) can increase the risk of heart disease.
Coronary heart disease	A condition where the coronary arteries become narrowed or blocked by fatty deposits (atherosclerosis), reducing blood flow to the heart. It can lead to heart attacks.
Health	A state of complete physical, mental, and social well-being, not just the absence of disease or illness.
Malignant	Describes a cancerous tumour that grows quickly and can spread to other parts of the body (metastasis).
Risk factor	Something that increases the chance of developing a disease or health problem.
Statin	A drug used to lower blood cholesterol levels and reduce the risk of heart disease.
Transplant	The medical process of moving an organ, tissue, or cells from one body (or part of the body) to another.
Tumour	A lump formed by uncontrolled cell division. Tumours can be benign (non-cancerous) or malignant (cancerous).
Antigens	A molecule (often a protein) found on the surface of a pathogen that is recognised as foreign by the immune system, triggering an immune response.
Antitoxins	Substances produced by white blood cells that neutralise toxins (poisons) made by bacteria.
Dose	The amount of a substance (like a drug or radiation) that is given or absorbed. In radiation, it's measured in sieverts (Sv).
Efficacy	In medicine, this refers to how well a drug produces the desired effect in treating a condition during clinical trials.
Herd immunity	When a large proportion of a population is immune (usually through vaccination), which helps protect individuals who are not immune, by reducing the spread of disease.
Mucus	A thick, slippery substance produced by the body to trap dust and microbes and protect surfaces like the lungs and digestive tract.
Peer review	The process where scientific work is checked by other experts in the same field before it is published to ensure accuracy and credibility.
Toxicity	The degree to which a substance can harm organisms; often tested when developing new drugs.
White blood cell	A type of blood cell that is part of the immune system and helps fight infection by destroying pathogens or producing antibodies.
Fungicide	A chemical used to kill or prevent the growth of fungi, especially in agriculture to protect crops from fungal diseases.
Isolation	Separating a substance or organism from others, for example, to prevent the spread of infection or to purify a chemical compound.
Mimic	In biology, when one organism copies the appearance or behaviour of another for protection or survival (e.g., avoiding predators).
Sexually transmitted disease (STD)	An infection passed from one person to another through sexual contact.
Toxin	A poisonous substance produced by organisms such as bacteria, which can cause illness or damage in other organisms
Vector	An organism that carries and transmits a pathogen to another living organism (e.g., a mosquito spreading malaria).
Allele	A different version of a gene. Each person inherits two alleles for each gene (one from each parent), which can be dominant or recessive.
Asexual reproduction	A type of reproduction that involves only one parent and produces genetically identical offspring (clones). It occurs in some plants, bacteria, and simple animals.
Characteristics	The features or traits of an organism, such as eye colour, blood type, or leaf shape. These can be inherited (genetic) or influenced by the environment.
Chromosomes	Thread-like structures found in the nucleus of cells. They are made of DNA and carry genes. Humans have 46 chromosomes (23 pairs).
Cystic Fibrosis	A genetic disorder caused by a recessive allele, leading to the production of thick, sticky mucus that affects the lungs and digestive system.
DNA	A large molecule that carries the genetic instructions for the development and function of living organisms.
Embryo	An early stage of development after fertilisation, where the cells begin to divide and differentiate to form a new organism.
Embryonic Screening	A technique used to test embryos for genetic disorders or specific genes, usually before implantation in IVF or during pregnancy.
Gamete	A sex cell (sperm in males, egg in females) that contains half the number of chromosomes. During fertilisation, two gametes fuse to form a zygote.
Genes	The plural of gene ? units of heredity that control the development of characteristics in living organisms by coding for proteins.
Genome	The entire set of genetic material (all the DNA, including all the genes) in an organism. The human genome has around 20,000?25,000 genes.
Inheritance	The process by which genetic information is passed from parents to offspring through genes.
Inherited Disorders	Genetic conditions passed down from parents to children, caused by faulty alleles.
Meiosis	A type of cell division that produces gametes (sperm and egg cells) with half the number of chromosomes; introduces genetic variation.
Offspring	The children or young produced by living organisms through reproduction.
Polydactyly	A genetic condition where a person is born with extra fingers or toes.
Proteins	Large molecules made of amino acids that perform many important functions in the body, such as building cells and enzymes.
Sexual Reproduction	A type of reproduction involving the fusion of male and female gametes, producing genetically varied offspring.
Variation	Differences in characteristics between individuals of the same species, caused by genetic and/or environmental factors.
Extinction	The permanent loss of all members of a species. Causes include habitat loss, climate change, disease, or competition.
Fossil record	The collection of fossils that provides evidence for how life on Earth has changed over time and supports the theory of evolution.
Antibiotic resistance	When bacteria evolve so that antibiotics no longer kill them. This can lead to infections that are harder to treat and is a major concern in medicine.
Natural selection	The process where organisms with advantageous traits are more likely to survive, reproduce, and pass on those traits.
Evolution	The gradual change in the characteristics of a species over time, driven by natural selection. It leads to the development of new species from earlier forms.
Embryo transplant	A method of cloning animals. An embryo is split into several identical parts, and each part is implanted into a different surrogate mother to develop into genetically identical offspring.
Genetically modified	An organism whose genetic material has been altered by adding genes from another organism to give it useful characteristics.
Genetic engineering	The process of altering the DNA of an organism by inserting genes from another organism to give it new traits.
Inbreeding	The breeding of closely related individuals, which can increase the risk of genetic disorders because harmful recessive alleles are more likely to be inherited.
Mutation	A random change in the DNA sequence of an organism's genes. It can be beneficial, harmful, or have no effect.
Selective breeding	The process where humans breed plants or animals for particular genetic traits.
Clone	An organism or cell that is genetically identical to the one from which it was produced. Cloning can occur naturally (e.g., identical twins) or artificially (e.g., in the lab or by cuttings in plants).
Dominant	An allele that expresses its trait in the phenotype even if only one copy is present. It masks the effect of a recessive allele.
Double helix	The shape of a DNA molecule, consisting of two strands twisted around each other, like a twisted ladder.
Fertilisation	The fusion of a male gamete (sperm) and a female gamete (egg) to form a zygote, which will develop into an embryo.
Gamete	A sex cell (sperm in males, egg in females) that contains half the number of chromosomes. During fertilisation, two gametes fuse to form a zygote.
Genome	The entire set of genetic material (all the DNA, including all the genes) in an organism. The human genome has around 20,000?25,000 genes.
Genotype	The genetic makeup of an organism ? the combination of alleles it has for a particular trait (e.g., Bb or bb). It determines the phenotype (what you see).
Heterozygous	Having two different alleles for a particular gene.
Meiosis	A type of cell division that produces gametes (sperm and egg cells) with half the number of chromosomes; introduces genetic variation.
Mitosis	A type of cell division that produces two genetically identical daughter cells for growth and repair.
Phenotype	The observable characteristics or traits of an organism, determined by its genes and environment (e.g. eye colour, height).
Punnett square	A diagram used to predict the possible genetic outcomes of offspring from a genetic cross.
Genetic cross	A diagram or method used to show how alleles are inherited from parents to offspring, often using a Punnett square to predict possible genotypes and phenotypes.
Recessive	A type of gene that only shows its effect if two copies are present (one from each parent).
Acid rain	Rainwater that is more acidic than normal, caused by sulfur dioxide (SO₂) and nitrogen oxides (NO_x) dissolving in rain. It can damage plants, aquatic life, and buildings.
Basalt	A fine-grained, dark volcanic rock formed from rapidly cooling lava. It is igneous and found in oceanic crust and volcanic regions.
Carbon cycle	The process by which carbon is recycled in the environment, involving processes like photosynthesis, respiration, decomposition, combustion, and fossil fuel formation. It ensures carbon is continuously reused.
Core	The central part of the Earth, made mainly of iron and nickel. It has a solid inner core and a liquid outer core, which contributes to Earth's magnetic field.
Crust	The outermost layer of the Earth, made up of solid rock. It includes continental and oceanic plates and is part of the lithosphere.
Crystals	Solid materials with particles arranged in a regular, repeating pattern. They often form during crystallisation.
Deposited	When a substance is laid down or settles, often from a solution or suspension. In geology and chemistry, it refers to materials being left behind after a liquid evaporates or cools.
Erosion	The process by which soil, rock, or land is worn away by forces such as wind, water, or ice. It can be natural or worsened by human activity like deforestation.
Evaporates	When a liquid changes into a gas at the surface, below its boiling point. This occurs when particles gain enough energy to escape.
Extrusive	A type of igneous rock formed when lava cools quickly on the Earth's surface, resulting in small crystals.
Global warming	The gradual increase in Earth's average temperature, mainly due to increased greenhouse gases (like carbon dioxide and methane) from human activities such as burning fossil fuels and deforestation.
Granite	A hard, igneous rock with large crystals, formed from slowly cooled magma underground. It is non-porous and often used in building materials.
Greenhouse effect	The natural process by which greenhouse gases trap heat (infrared radiation) in Earth?s atmosphere, keeping the planet warm enough to support life.
Greenhouse gases	The group of gases in the atmosphere that trap heat and contribute to global warming. These include CO₂, CH₄, N₂O, and water vapour.
Igneous rock	A type of rock formed from cooled magma or lava. It can be intrusive (cools slowly underground, e.g., granite) or extrusive (cools quickly on the surface, e.g., basalt).
Intrusive	Rock formed when magma cools slowly below the Earth's surface, creating large crystals.
Layers	In science, this often refers to structural arrangements, such as rock layers (geology), atmospheric layers, or layers of skin.
Magma	Molten rock beneath the Earth?s surface that can erupt as lava during volcanic activity.
Mantle	The thick layer of hot, semi-solid rock between the Earth?s crust and core; involved in tectonic activity.
Marble	A metamorphic rock formed when limestone is subjected to heat and pressure; used in buildings and sculptures.
Metamorphic rock	Rock formed when existing rock is changed by heat and pressure without melting, e.g. limestone turning into marble.
Minerals	Naturally occurring solid substances with a definite chemical composition and crystalline structure.
Non-porous rock	A type of rock that does not allow water or air to pass through it because it has no spaces (pores), e.g. granite.
Physical weathering	The breakdown of rocks without chemical change, often caused by temperature changes (freeze-thaw) or physical forces like wind or water.
Rock cycle	The continuous process by which rocks are formed, broken down, and transformed into different types of rocks (igneous, sedimentary, and metamorphic).
Sediment	Small particles of rock, soil, or organic material that settle at the bottom of a liquid.
Sedimentary rock	Rock formed by the compression and cementation of layers of sediment.
Slate	A fine-grained metamorphic rock that can be split into thin layers, often used for roofing or writing slates.
Strata	Layers of sedimentary rock formed over time, often containing fossils that provide clues about Earth?s history.
Transported	Refers to the movement of substances, such as ions or molecules, often during chemical reactions or separation processes.
Weathering	The breakdown of rocks and minerals at the Earth?s surface due to physical, chemical, or biological processes.
Force	A push or pull on an object, measured in newtons (N). Forces can cause objects to start moving, stop, change speed, direction, or shape.
Fluid	A substance that flows, meaning it has no fixed shape. Includes liquids and gases.
Gas	A state of matter where particles are far apart and move freely in all directions. Gases have no fixed shape or volume and can be compressed easily.
Hydraulic	Refers to systems using liquid pressure (usually water or oil) to transmit force.
Pascal (Pa)	The SI unit of pressure. One pascal is equal to one newton per square metre (1 Pa = 1 N/m²).
Pivot	The fixed point around which a lever or object rotates or turns ? important in calculations involving moments (turning forces).
Pressure	The force applied per unit area on a surface. It is measured in pascals (Pa).
Lever	A simple machine consisting of a rigid bar that pivots around a fixed point (fulcrum) to move a load with less effort.
Liquid	A state of matter with a definite volume but no fixed shape; particles can move past one another freely.
Load	The weight or resistance that a machine or structure supports or moves; in physics, it's often used when studying forces in levers and structures.
Metre (m)	The SI base unit of length in the metric system. One metre = 100 centimetres.
Moment	The turning effect of a force around a pivot
Newton (N)	The unit of force in the International System of Units (SI). One newton is the force needed to accelerate a 1 kg mass by 1 m/s².
Newton metre (Nm)	The unit of moment (turning force). One newton metre is the moment produced by a force of 1 newton acting 1 metre from a pivot.
Square metre (m²)	The SI unit of area, equal to the area of a square with sides 1 metre long.
Volume	The amount of space an object or substance occupies, measured in cubic units (e.g., cm³, m³).
Effort	The force applied to a machine (like a lever) to move a load.
Adaptation	A feature or characteristic that helps an organism survive and reproduce in its environment. Adaptations can be structural, behavioural, or functional.
Ancestors	Organisms from which later organisms have evolved. Your ancestors are the species or individuals from the past that you are genetically descended from.
Animals	A kingdom of multicellular organisms that are heterotrophic (they consume other organisms for energy), usually mobile, and do not have cell walls. Examples include humans, birds, and insects.
Biodiversity	The variety of different species of plants, animals, and microorganisms living in an ecosystem or on Earth as a whole. High biodiversity helps ecosystems stay stable and resilient.
Characteristics	The features or traits of an organism, such as eye colour, blood type, or leaf shape. These can be inherited (genetic) or influenced by the environment.
Chordates	Animals that belong to the phylum Chordata. They have a notochord (a supportive rod) at some stage in development. This group includes vertebrates like mammals, birds, and fish.
Class	A level of classification in the biological taxonomy system. For example, mammals form a class within the animal kingdom.
Conservation status	A classification that describes the risk of extinction of a species. Categories include Least Concern, Vulnerable, Endangered, and Critically Endangered.
Continuous variation	A type of variation that shows a range of values with no distinct categories, such as height or mass. It is usually influenced by both genes and the environment.
Descendants	The offspring or future generations of an organism. In biology, descendants inherit genetic traits from their ancestors.
Discontinuous variation	A type of variation where individuals fall into distinct groups or categories with no intermediates. Examples include blood type or ability to roll the tongue. It is usually controlled by one or a few genes.
DNA	A large molecule that carries the genetic instructions for the development and function of living organisms.
Endangered	A species that is at risk of extinction because its population is very low or its habitat is under threat.
Environmental	Relating to the natural world, including living organisms, air, water, land, and the effects of human activity on these.
Evolution	The gradual change in the characteristics of a species over time, driven by natural selection. It leads to the development of new species from earlier forms.
Extinct	When a species has no living members left anywhere on Earth ? it has died out completely.
Families	Groups of elements with similar chemical properties, usually found in the same vertical column of the periodic table.
Fungi	A kingdom of living organisms including mushrooms, yeasts, and moulds. They are decomposers, breaking down organic matter, and do not photosynthesise.
Gene bank	A place where genetic material (like seeds, eggs, sperm, or DNA) is stored for future use, often for conservation or breeding programs.
Genes	The plural of gene ? units of heredity that control the development of characteristics in living organisms by coding for proteins.
Genetic modification	The process of altering the DNA of an organism by inserting genes from another organism to give it new traits.
Genus	A rank in biological classification above species and below family. A genus groups closely related species.
Inherited Disorders	Genetic conditions passed down from parents to children, caused by faulty alleles.
Keys	Tools used in classification to identify organisms or substances based on a series of choices that lead the user to the correct name.
Kingdom	One of the highest taxonomic groups in biological classification. Examples include Animalia (animals), Plantae (plants), Fungi, and Protista.
Natural selection	The process where organisms with advantageous traits are more likely to survive, reproduce, and pass on those traits.
Order	A level in the biological classification system, ranking below class and above family
Phylum	A classification level in the biological hierarchy below kingdom and above class; it groups organisms with similar body plans or features (e.g. Chordata for animals with a backbone).
Plants	Living organisms that typically produce their own food through photosynthesis using sunlight, water, and carbon dioxide. They have roots, stems, and leaves.
Prokaryote	A simple type of cell without a nucleus, found in bacteria.
Protoctista	A group of mostly single-celled organisms, like algae and protozoa, that don?t fit into animals, plants, or fungi.
Seedbank	A facility or natural storage place where seeds are stored to preserve genetic diversity for future use.
Selective breeding	The process where humans breed plants or animals for particular genetic traits.
Species	A group of organisms that can breed together to produce fertile offspring.
Variation	Differences in characteristics between individuals of the same species, caused by genetic and/or environmental factors.
Attraction	A force that pulls objects together. For example, there is attraction between oppositely charged ions or between magnets and magnetic materials.
Fleming's left hand rule	A rule used to predict the direction of force on a current-carrying wire in a magnetic field.
Induced	Caused or triggered by an external action.
Magnetic field	The region around a magnet where magnetic forces can be felt; represented by field lines from north to south pole.
Magnetic Flux Density	A measure of the strength of a magnetic field; represented by the symbol B and measured in tesla (T).
Non-contact Force	A force that acts between objects without them touching, such as gravity, magnetic force, or electrostatic force.
Poles	The ends of a magnet where the magnetic force is strongest; called the north and south poles.
Repulsion	The force that pushes two objects or charges away from each other.
Solenoid	A coil of wire that produces a magnetic field when an electric current passes through it.
Electromagnet	A magnet created by passing current through a coil of wire (often wrapped around an iron core). It can be switched on and off and used in devices like relays or electric bells.
Motor effect	The force experienced by a current-carrying wire in a magnetic field; basis for how electric motors work.
Split-ring commutator	A device in an electric motor that reverses the direction of current every half turn to keep the motor spinning in one direction.
Permanent	Often refers to a permanent magnet, which retains its magnetic properties without being in a magnetic field or needing electricity.
Alkane	A type of hydrocarbon that contains only single bonds between carbon atoms. They are saturated compounds (e.g. methane, ethane).
Alkene	A type of hydrocarbon that contains at least one carbon-carbon double bond. They are unsaturated compounds (e.g. ethene, propene).
Catalytic Cracking	A process in which long-chain hydrocarbons are broken down into shorter, more useful molecules (like alkanes and alkenes) using a catalyst and heat. Used in the oil industry.
Complete Combustion	A type of combustion that happens when there is plenty of oxygen. It produces carbon dioxide and water, and releases the maximum amount of energy.
Crude Oil	A mixture of hydrocarbons found underground or under the sea. It is unrefined petroleum and must be separated by fractional distillation to make useful fuels like petrol and diesel.
Decolourising	The process of removing colour from a substance. In chemistry, it often refers to a reaction where a coloured compound becomes colourless, e.g. bromine water decolourising when alkenes are present.
Fraction	In chemistry, a group of hydrocarbons with similar boiling points obtained during fractional distillation of crude oil.
Fractional Distillation	A method used to separate a mixture of liquids (like crude oil) based on their different boiling points. Substances with lower boiling points are collected first.
Homologous Series	A group of organic compounds (e.g., alkanes, alkenes) that have the same general formula, similar chemical properties, and show a gradual change in physical properties.
Hydrocarbon	A compound made only of hydrogen and carbon atoms. Found in crude oil and natural gas, and used as fuels.
Incomplete Combustion	A combustion reaction where there is not enough oxygen, producing carbon monoxide (CO) or soot (carbon) instead of just carbon dioxide and water. It releases less energy and is more dangerous.
Saturated	A solution that contains the maximum amount of dissolved solute at a given temperature.
Unsaturated	refers to a compound (usually a hydrocarbon) that contains at least one double or triple bond between carbon atoms, meaning it can react with more atoms (e.g., alkenes).
Viscous	Describes a liquid that is thick and resists flowing easily.
Volatile	Describes a substance that evaporates easily at room temperature due to weak intermolecular forces (e.g., ethanol).
Boiling point	The temperature at which a liquid turns into a gas (boils). For water at standard pressure, it is 100°C.
Combustion	A chemical reaction in which a substance reacts with oxygen, releasing heat and light (exothermic).
Feedstock	A raw material used in an industrial process. In chemistry, it usually refers to substances used to make chemicals or fuels, such as crude oil fractions.
Flammability	A measure of how easily a substance catches fire and burns in air.
Fuel	A substance that releases energy when it burns, often used for power or heating.
Viscosity	A measure of how thick or resistant to flow a liquid is. A high-viscosity liquid (like honey) flows more slowly than a low-viscosity one (like water).
Fluidity	How easily a fluid flows ? the ability to flow freely. Liquids with high fluidity flow quickly (like water), while those with low fluidity flow slowly (like syrup).
Alveoli	Tiny air sacs in the lungs where gas exchange occurs. Oxygen diffuses into the blood and carbon dioxide diffuses out. They have a large surface area, thin walls, and a rich blood supply to make gas exchange efficient.
Antibody	A single molecule of the protein that binds to a specific antigen. Each antibody is specific to one type of antigen.
Antitoxin	Substances produced by white blood cells that neutralise toxins (poisons) made by bacteria.
Aorta	The largest artery in the body. It carries oxygenated blood from the left ventricle of the heart to the rest of the body.
Artery	A type of blood vessel that carries blood away from the heart. Most arteries carry oxygenated blood and have thick, muscular walls to handle high pressure.
Atrium	One of the upper chambers of the heart. The left atrium receives oxygenated blood from the lungs, and the right atrium receives deoxygenated blood from the body.
Capillary	The smallest type of blood vessel. Capillaries have thin walls (one cell thick) to allow exchange of substances like oxygen, carbon dioxide, and glucose between the blood and tissues.
Carbohydrate	A macronutrient made of carbon, hydrogen, and oxygen. It provides energy to the body. Examples include sugars and starches.
Cell	The basic unit of life in all living organisms. Cells can be prokaryotic (like bacteria) or eukaryotic (like animal and plant cells).
Deoxygenated	Describes blood that has little or no oxygen. It returns to the right side of the heart from the body and is then pumped to the lungs to pick up oxygen.
Enzyme	A biological catalyst that speeds up a chemical reaction in living organisms without being used up. Each enzyme is specific to a particular reaction.
Epidermal	The outer layer of cells on the surface of a plant or animal, providing protection. In plants, epidermal tissue helps reduce water loss and protect against pathogens.
Gland	An organ that produces and releases hormones or other substances.
Intestine	A part of the digestive system where food is broken down and nutrients are absorbed.
Lipid	A type of biological molecule that includes fats and oils; used for energy storage, insulation, and making cell membranes.
Liver	A large organ in the body that performs many functions including detoxifying chemicals, producing bile, and breaking down substances like alcohol and drugs.
Mesophyll	The inner tissue of a leaf where most photosynthesis takes place. It includes palisade and spongy mesophyll cells.
Oxygenated	Refers to blood that is rich in oxygen, usually found in arteries (except the pulmonary artery)
Pancreas	A gland that produces digestive enzymes and the hormones insulin and glucagon to regulate blood sugar levels.
Phloem	The tissue in plants that transports dissolved sugars (mainly sucrose) from the leaves to the rest of the plant.
Plasma	The yellowish liquid part of blood that carries cells, nutrients, hormones, and waste products around the body.
Platelet	A small blood cell that helps with blood clotting to stop bleeding when you get a cut.
Protein	Large molecules made of amino acids that perform many important functions in the body, such as building cells and enzymes.
Pulmonary	Related to the lungs.
Stomach	A muscular organ in the digestive system that breaks down food using enzymes and stomach acid.
Stomata	Tiny pores on the surface of leaves that allow gases (like carbon dioxide and oxygen) to enter and leave the plant.
Tissue	A group of similar cells working together to perform a specific function (e.g., muscle tissue, nervous tissue).
Translocation	The movement of dissolved sugars and other substances in the phloem of a plant from where they are made (sources) to where they are needed (sinks).
Transpiration	The loss of water vapour from the leaves of a plant through the stomata. It helps pull water up from the roots.
Vein	A blood vessel that carries blood towards the heart, usually low in oxygen (except the pulmonary vein).
Ventricle	One of the two lower chambers of the heart that pump blood out to the lungs (right ventricle) or the rest of the body (left ventricle).
Villi	Small finger-like projections lining the small intestine that increase the surface area for the absorption of digested food.
Xylem	Plant tissue that transports water and mineral ions from the roots to the rest of the plant. It also provides structural support.
Bronchi	The two main air passages that branch off from the trachea and carry air into each lung.
Bronchiole	Small branches of the bronchi within the lungs that carry air to the alveoli where gas exchange occurs.
Cardiac	Relating to the heart. For example, cardiac muscle is the special muscle that makes up the heart.
Coronary	Relating to the blood vessels (coronary arteries) that supply the heart muscle with oxygenated blood.
Double circulatory system	A circulatory system where the blood passes through the heart twice for every full circuit of the body
Valve	A structure in the heart and veins that prevents the backflow of blood, ensuring it flows in one direction.
Vena cava	A blood vessel that carries blood towards the heart, usually low in oxygen (except the pulmonary vein).
Photosynthesis	The process by which green plants use light energy to convert carbon dioxide and water into glucose and oxygen:
Temperature	A measure of how hot or cold something is, indicating the average kinetic energy of particles in a substance.
Guard cells	Specialised cells on either side of a stomata (pore) in plant leaves. They control the opening and closing of the stomata to regulate gas exchange and water loss.
Humidity	The amount of water vapour in the air. High humidity means the air holds more moisture.
Wind speed	The rate at which air is moving, often measured using an anemometer; relevant in ecology for measuring abiotic factors.
Active site	The specific part of an enzyme where the substrate binds. It has a unique shape that fits only one type of substrate.
Catalyse	To speed up a chemical reaction without being used up itself. Enzymes are biological catalysts.
Denatured	When a protein (like an enzyme) changes shape due to heat or extreme pH, and no longer functions properly because its active site is altered.
Lipase	An enzyme that breaks down lipids (fats) into fatty acids and glycerol in the digestive system.
Optimum	The best or most favourable condition for a process or reaction to happen, such as the optimum temperature or pH for enzyme activity.
Organ	A group of different tissues working together to perform a specific function in an organism (e.g. the heart or liver).
Organ system	A group of organs that work together to carry out a major body function (e.g. the digestive system or respiratory system).
pH	A scale from 0 to 14 that measures how acidic or alkaline a solution is.
Protease	An enzyme that breaks down proteins into smaller peptides or amino acids.
Substrate	The substance on which an enzyme acts during a chemical reaction.
Density	The mass per unit volume of a substance.
Displacement	A reaction where a more reactive element replaces a less reactive one in a compound.
Internal Energy	The total energy stored inside a system, made up of the kinetic energy (movement) and potential energy (position) of particles.
Latent Heat	The energy required for a substance to change state (e.g. from solid to liquid or liquid to gas) without changing temperature.
Matter	Anything that has mass and takes up space (volume); exists as solids, liquids, or gases.
Potential Energy	Energy stored in an object due to its position or condition (like a raised object or stretched spring).
Boil	A localized infection of the skin, often caused by bacteria, resulting in a swollen, red, painful lump filled with pus.
Condense	The process by which a gas turns into a liquid, usually when cooled. This is the opposite of evaporation or boiling.
Melt	The process by which a solid turns into a liquid when heated to its melting point.
Solidify	The process where a liquid changes into a solid, usually by cooling.
Sublimation	The change of state from a solid directly to a gas (or gas to solid) without passing through the liquid state (e.g., dry ice).
Avogadro's constant	The number of particles (atoms, molecules, or ions) in one mole of a substance. It is 6.022 ? 10²³ particles per mole.
Concentration	The amount of a substance (solute) dissolved in a certain volume of solvent or solution.
Conservation of Mass	A principle stating that mass is not lost or gained in a chemical reaction. The total mass of reactants equals the total mass of products.
Dilution	The process of adding more solvent (usually water) to a solution to make it less concentrated.
Isotope	Atoms of the same element that have the same number of protons but different numbers of neutrons.
Limiting Reactants	The substance in a chemical reaction that is used up first, limiting the amount of product that can be formed.
Mole	A unit used to measure the amount of a substance; one mole contains 6.02x10²³ particles (Avogadro's number).
Neutralisation	A chemical reaction in which an acid and a base react to form a salt and water, cancelling each other out.
Reacting Masses	The amounts (mass) of substances that react together in a chemical reaction, based on their proportions in the balanced equation.
Relative Atomic Mass (A_r)	The average mass of an atom of an element compared to 1/12th of the mass of a carbon-12 atom.
Relative Formula Mass (M_r)	The sum of the relative atomic masses of all the atoms in a chemical formula.
Excess	An amount that is more than needed. In chemistry, an excess reactant is one that is not completely used up in a reaction.
Formula	A way of showing the elements in a compound and the ratio of atoms using symbols and numbers.
Mass	The amount of matter in an object; measured in kilograms (kg) and not affected by gravity.
Activity	The rate at which a radioactive source decays, measured in becquerels (Bq). One becquerel equals one decay per second.
Alpha Decay	A type of radioactive decay where an unstable nucleus emits an alpha particle, which consists of two protons and two neutrons (the same as a helium nucleus). This process decreases the atomic number by 2 and the mass number by 4.
Atomic Models	Different representations of the structure of the atom, such as the plum pudding model, Bohr model, and the nuclear model, developed as scientific understanding improved.
Beta Decay	A type of radioactive decay where a neutron changes into a proton, and a beta particle (a high-speed electron) is emitted. The atomic number increases by 1, but the mass number stays the same.
Contamination	The unwanted presence of a substance, often harmful, such as radioactive material, bacteria, or toxic chemicals. It can make things unsafe or affect scientific results.
Electrons	A tiny negatively charged particle that orbits the nucleus of an atom in energy levels (shells). Electrons are involved in chemical bonding and electric current.
Gamma Radiation	A type of electromagnetic radiation with very short wavelength and high energy, emitted from the nucleus of radioactive atoms. It is highly penetrating and used in cancer treatment and sterilisation.
Half Life	The time it takes for half of the radioactive nuclei in a sample to decay. Used to measure radioactive stability and for dating fossils.
Irradiation	The process of exposing objects to radiation, often used to kill bacteria in food or sterilize medical equipment.
Isotope	Atoms of the same element that have the same number of protons but different numbers of neutrons.
Neutrons	A neutral subatomic particle found in the nucleus of an atom. It has no charge and a mass similar to a proton.
Nucleon	A particle found in the nucleus of an atom - either a proton or a neutron.
Nucleus	The central part of an atom containing protons and neutrons.
Plumb Pudding Model	An early atomic model proposed by J.J. Thomson where the atom is pictured as a sphere of positive charge with electrons scattered inside like "plums" in a pudding.
Protons	Positively charged particles in the nucleus of an atom; they determine the atomic number of an element.
Radioactivity	The process by which unstable atomic nuclei lose energy by emitting radiation.
Scattering Experiment	An experiment where particles (like alpha particles) are fired at a target to study the structure of atoms (e.g., Rutherford?s experiment).
Tangent	A straight line that touches a curve at one point only. Used to find the gradient (rate of change) on a distance-time or velocity-time graph.
Activation Energy	The minimum amount of energy needed for a chemical reaction to start. Enzymes lower the activation energy required.
Catalyst	A substance that speeds up a chemical reaction without being used up or changed in the process. It lowers the activation energy needed for the reaction.
Collision Theory	A theory that explains how chemical reactions occur. It states that particles must collide with enough energy (activation energy) and in the correct orientation for a reaction to happen.
Collisions per Second	A way of describing the frequency of collisions between reacting particles. The more collisions per second, the faster the reaction rate.
Concentration	The amount of a substance (solute) dissolved in a certain volume of solvent or solution.
Dynamic equilibrium	In a reversible reaction, dynamic equilibrium occurs when the forward and backward reactions happen at the same rate, and the concentrations of reactants and products remain constant.
Gas Syringe	A piece of lab equipment used to collect and measure the volume of a gas produced in a chemical reaction, often in cm?.
Heat Energy	A form of energy that causes an object to increase in temperature. It is transferred from hotter objects to cooler ones until equilibrium is reached.
Precipitation	A chemical reaction where a solid forms and separates out from a solution.
Pressure	The force exerted by gas particles colliding with the walls of their container, measured in pascals (Pa).
Proportional	When two quantities change at the same rate; if one doubles, the other doubles too.
Rate of reaction	How fast a chemical reaction happens, usually measured by the amount of product formed or reactant used per time.
Reversible reaction	A chemical reaction where the products can change back into the reactants.
Surface Area	The total area of the exposed surface of an object or substance. In chemistry, a higher surface area (e.g., powdered solid) can speed up reactions.
Tangent	meaning a straight line that touches a curve at one point without crossing it.
Collision	When two or more particles or objects hit each other. In chemical reactions, collisions between reactant particles are needed for reactions to occur.
Closed system	A system where no matter can enter or leave, but energy can be transferred. In chemistry and physics, it means the mass stays constant, even if energy changes.
Conditions	The specific factors or environment needed for a reaction or process to occur, such as temperature, pressure, pH, or light intensity.
Frequency of collisions	How often reacting particles collide with each other. A higher frequency of collisions usually means a faster reaction rate.
Gradient	A measure of the steepness of a graph line, often used to find speed in a distance?time graph or acceleration in a velocity?time graph.
Le Chatelier's principle	If a change is made to a system at equilibrium, the system responds to counteract the change and restore equilibrium.
Aeration	The process of adding air (oxygen) to a substance, such as soil or water, to improve conditions for aerobic organisms like plant roots or bacteria.
Aerobic Digestion	A process in which microorganisms break down organic matter in the presence of oxygen, often used in sewage treatment to reduce waste.
Anaerobic Digestion	The breakdown of organic material by microorganisms without oxygen, often used to produce biogas (mainly methane) from waste like food or sewage.
Bioleaching	A process that uses bacteria to extract metals from low-grade ores by breaking down the ore and producing a solution containing the metal (a leachate).
Blackwater	Wastewater that contains human waste (e.g. from toilets). It needs to be treated before being safely released into the environment.
Filtering	A separation process where a solid is removed from a liquid using a filter. Common in water purification or chemistry experiments.
Finite resources	Resources that are limited in supply and will run out if overused, because they are not replaced quickly.
Greywater	Wastewater from sinks, baths, showers, and washing machines (not toilets). It can sometimes be recycled for watering plants or flushing toilets.
Life Cycle Assessments (LCAs)	A method for assessing the environmental impact of a product throughout its entire life ? from raw material extraction to disposal.
Phytomining	A method of extracting metals from soil by growing plants that absorb metal compounds; the plants are then burned and the metals extracted from the ash.
Potable Water	Water that is safe to drink.
Recycling	The process of recovering and reusing materials to reduce waste and conserve resources.
Resources	Natural materials used by humans, such as minerals, water, and fossil fuels.
Sustainability	Using resources in a way that meets current needs without harming the environment or using up resources for future generations.
Sustainable Development	Development that balances economic growth, environmental care, and social well-being for long-term benefit.
Leaching	The process by which soluble substances are washed out from soil or waste materials, often by rainwater.
Biodegradable	A substance that can be broken down naturally by microorganisms (like bacteria or fungi) into harmless substances over time.
Distillation	A method used to separate mixtures based on differences in boiling points. A liquid is heated until it evaporates, then cooled and condensed into a separate container.
Effluent	Wastewater (liquid waste) that is discharged into the environment, especially from factories or sewage treatment works. It must be treated to remove harmful substances.
Renewable resources	Natural resources that can be replaced or regenerated quickly and are not depleted by use (e.g., solar energy, wind).
Reverse osmosis	A process that removes impurities from water by forcing it through a semi-permeable membrane.
Screening	A process used to separate solids of different sizes by passing them through screens or sieves.
Sedimentation	The process by which sediment settles out of a fluid (water or air) and accumulates.
Sewage	Waste water and excrement that is carried away from buildings through drains or sewers.
Sludge	Thick, semi-solid waste material produced during sewage or industrial wastewater treatment.
Sterilisation	The process of killing or removing all microorganisms to prevent contamination, often used in food, medicine, and lab work.
Amplitude	The maximum displacement of a wave from its rest position. It shows how much energy the wave carries - larger amplitude = more energy.
Angle of Incidence	The angle between the incoming ray (incident ray) and the normal (a line at 90° to the surface) at the point where the ray hits a surface.
Angle of Reflection	The angle between the reflected ray and the normal at the point of reflection. According to the law of reflection, it is equal to the angle of incidence.
Compression	A region in a longitudinal wave (like sound) where the particles are close together. Also refers to squeezing a material, reducing its volume.
Displacement	A reaction where a more reactive element replaces a less reactive one in a compound.
Echo	A sound wave that is reflected off a surface (like a wall or cliff) and heard again. Used in applications like ultrasound scanning and sonar.
Electromagnetic Spectrum	The range of all types of electromagnetic waves, arranged by wavelength or frequency.
Frequency	The number of waves that pass a point per second, measured in hertz (Hz).
Gamma Rays	A type of electromagnetic radiation with very short wavelength and high energy, emitted from the nucleus of radioactive atoms. It is highly penetrating and used in cancer treatment and sterilisation.
Infrared	A type of electromagnetic radiation with longer wavelengths than visible light. It is emitted by warm objects and used in thermal imaging and remote controls.
Ionosphere	A region of Earth?s upper atmosphere that is ionized by solar radiation and is important for radio communication as it reflects radio waves.
Longitudinal	A type of wave where the vibrations are parallel to the direction the wave travels, e.g. sound waves.
Microwaves	A type of electromagnetic wave used in cooking and communication, such as mobile phones and satellite signals.
Period	The time taken for one complete cycle of a wave or oscillation.
Radio waves	Electromagnetic waves with the longest wavelength, used for communication like radio and TV signals.
Rarefaction	A region in a longitudinal wave where particles are spread apart, causing a decrease in pressure.
Reflection	When a wave (like light or sound) bounces off a surface.
Refraction	The bending of a wave as it passes from one material to another.
Total Internal Reflection	When a wave (like light) hits a boundary at a large angle and is completely reflected back into a material instead of passing through. Happens when moving from a dense to a less dense medium.
Transverse	A type of wave where the oscillations are perpendicular to the direction the wave travels (e.g., light waves, water waves).
Ultraviolet	A type of electromagnetic radiation with wavelengths shorter than visible light. It can cause skin damage and is used in sterilisation.
Visible Light	The part of the electromagnetic spectrum that can be seen by the human eye, ranging from red to violet.
Wavefront	A line or surface joining points where the wave has the same phase (e.g., all the crests of a wave). It shows the direction the wave is moving.
Wavelength	The distance between two corresponding points on a wave (e.g., crest to crest or trough to trough). It is usually measured in metres (m).
X-Rays	A type of high-energy electromagnetic radiation used in medicine to view inside the body. They can pass through soft tissue but are absorbed by bone.

This page was updated on: 1st July 2025