Doc Brown's GCSE OCR Gateway Science-Chemistry Revision Notes

OCR GCSE Gateway Additional Science Chemistry Module C3 Chemical Economics

Unit-Item C3f Energy

1. This unit develops ideas about how the amount of energy released during chemical reactions such as combustion can be measured.

2. Ideas about bond forming and bond breaking are used to explain why reactions are exothermic or endothermic.

3. Practical work and research investigations-activities which you have done which help in revision may have included:

   • Carry out experiments to find out about exothermic and endothermic reactions (with the option of using data loggers).

   • Measure the energy released per gram during the combustion of butane and the combustion of some liquid fuels – possible use of spreadsheets to analyse results.

   • Compare the energy output from a blue and from a yellow Bunsen flame.

4. Know that an exothermic reaction is one in which energy is transferred into the surroundings (releases energy).

5. Know that an endothermic reaction is one in which energy is taken from the surroundings (absorbs energy).

6. Be able to recognise exothermic and endothermic reactions using temperature changes.

7. Be able to describe, using a diagram, a simple calorimetric method for comparing the energy transferred in combustion reactions:

   • a) use of spirit burner or a bottled gas burner

   • b) heating water in a copper calorimeter

   • c) measuring the temperature change

   • d) fair tests.

8. Be able to interpret and use data from simple calorimetric experiments related to the combustion of fuels to compare which fuel releases the most energy.

9. Know bond making as an exothermic process and bond breaking as an endothermic process.

10. HT only: Be able to explain why a reaction is exothermic or endothermic using the energy changes that occur during bond breaking and bond making.

11. Be able to describe a simple calorimetric method for comparing the energy transferred per gram of fuel combusted:

    • a) use of spirit burner or a bottled gas burner

    • b) heating water in a copper calorimeter

    • c) measuring mass of fuel burnt

    • d) measuring temperature change

    • e) fair and reliable tests.

12. Be able to calculate the energy transferred by using the formula (no recall needed):

    • energy transferred (in J) = m × c × ΔT

      • where m = mass of water heated in g

      • c = specific heat capacity (4.2 J/g °C)

      • ΔT = temperature change.

13. HT only: Be able to use the formula energy transferred (in J) = m × c × ΔT to calculate:

    • m = mass of water heated in g

    • ΔT = temperature change.

14. HT only: Be able to calculate the energy output of a fuel in J/g by knowing and using the formula:

    • energy per gram = energy released (in J) / mass of fuel burnt (in g)

15. Notes and quizzes:

    • Notes on Energy changes-transfers in Chemical Reactions - Exothermic and endothermic energy changes

    • Multiple choice quiz on Energy Changes in Chemical Reactions