What is being taught lesson by lesson:
- Earth’s resources and sustainable development.
- Potable water.
- Required practical – water purification and testing for ions.
- Wastewater treatment.
- Alternative methods of extracting metals.
- Life Cycle Assessments (LCAs) and recycling.
- Reducing our needs for resources.
Key Terms for this topic (Tier 3 vocabulary)
Resources – sustainability – sustainable development – bioleaching – phytomining – life cycle assessments – potable water – screening – aerobic digestion – anaerobic digestion.
What everyone needs to know:
Our resources come from the Earth, whether is is food grown in its soil, fuel from trees, coal and oil or minerals mined from its crust, the Earth, its atmosphere and oceans are the sources that sustains life. These resources are finite.
Chemistry is vital in making these resources more sustainable for future generations. You need to tell the difference between finite and renewable resources. Information may come in the form of graphs and data tables for you to interpret.
Potable water is safe drinking water. Chemically it is not pure as it has a variety of dissolved ions and gases. In different parts of the world, different methods are used to make water safe to drink.
In the UK –
- We use rainwater in lakes and rivers as it has very little dissolved in it.
- We then pass this through filter beds to remove sediments.
- Then sterilise the water with chlorine, ozone or UV light.
You need to be able to describe these stages and state why each one is competed. In countries that do not have our rainfall levels, desalination (removing salt) is an option. Here, fresh water is taken from sea water in the expensive process of wither distillation or reverse osmosis.
Required practical 13 – Analyse and purify samples of water from different sources, test the pH and ions dissolved in it.
When potable leaves our homes, businesses and factories, it needs to be treated before returning to rivers and the sea.
- Sewage is screened to remove grit.
- Then the sediments settles and the sludge is removed.
- The sewage sludge is attacked by bacteria for anaerobic digestion to break it down.
- Finally, aerobic treatment from microbes to break down the last of the biological matter.
You should be able to describe that potable water is relatively easy to get from wastewater. Look at developments such as the lifestraw.
Life cycle assessments (LCAs) assess the impact a product has on the environment from start to finish:
- Obtaining the raw materials and processing them,
- Making it and its packaging,
- How it is used through its life
- Disposal and any transport.
You need to be able to evaluate data to se which products have the biggest impact on the environment. The most common one is the comparison between paper and plastic shopping bags.
Finally, you need to be able to show ways of reducing the use of resources. Starting with Reduce, Reuse and Recycle. Look into a variety of materials like glass, ceramics, metals and plastics, see how they affect the environment from oil exploration to giant pen quarries. Given data, you need to be able to evaluate ways of reducing the use of our limited resources.
Extra topics needed for the Higher papers:
Because we use so much metal for our modern lives, the easily obtained/high grade ores are mostly gone so we need better ways of getting low grade ores out.
Phytomining involved growing plants in soil containing metals. Harvest the plants then burn them. You can collect the metals from the ash. This method is also used to decontaminate soil that contains toxic metals.
Bioleaching relies on bacteria to make leachate solutions rich in these metals which can be electrolysed.