Required Practical 10: Temperature Changes
About this practical...
When chemical reactions occur, there is a change in energy. In this practical, you will be able to measure that change and work out the energy change. The level of complexity can vary, you can record a temperature change; work out an energy change using the specific heat capacity of water; energy change per gram of reactant and finally, you could work out the energy change per mole. Key learning is also around assessing the practical's reliability and accuracy. Look at ways of improving this experiment to get consistent answers around the class.
Method:
1. Into a polystyrene cup, add 50cm3 of tap water
2. For improved stability, stand the cup inside a glass beaker
3. Place a thermometer into the water and record the initial temperature
4. Carefully measure out 5g of calcium chloride (replace the lid)
5. Add the calcium chloride to the water and place plastic lid on and put the thermometer through the hole into the solution
6. Record the highest/lowest temperature achieved = final temperature.
7. Calculate the temperature change ="initial temperature" and "final temperature".
8. Once completed, your teacher may ask you to repeat the same experiment to assess accuracy or to repeat with a different mass of calcium chloride to see if you get the same energy grange per gram (or mole), which you should.
9. Energy change = mass of water (50) x temperature change x 4.2 (SHC of water)
10. To find the energy change per gram, divide the above answer by 5 (as 5g added).
(Higher tier) - try to calculate the energy change per mole.
Safety & Managing Risks
Usual lab rules must be followed: loose hair tied back, goggles worn throughout the lesson, bags and stools tucked away and notify the teacher of any spills or breakages immediately. Take care with the chemicals as some generate heat and can burn. For more detailed information, please consult CLEAPSS.
Technician notes:
Small pots of calcium chloride with screw on lids
Spatulas
Balances
Weighing boats
Polystyrene cups
Glass beakers into which the cups can stand
Plastic lids with centre holes
short thermometers (best stability)
This page was updated on: 8th January 2022