Energy changes are an important part of chemical reactions. The interaction of particles often involves transfers of energy due to the breaking and formation of bonds. Reactions in which energy is released to the surroundings are exothermic reactions, while those that take in thermal energy are endothermic. These interactions between particles can produce heating or cooling effects that are used in a range of everyday applications. Some interactions between ions in an electrolyte result in the production of electricity. Cells and batteries use these chemical reactions to provide electricity. Electricity can also be used to decompose ionic substances and is a useful means of producing elements that are too expensive to extract any other way.

Specification links:

Set 1 - 4.5.1.1 - 4.5.2.2

Set 2 - 5.5.1.1 - 5.5.1.3

Set 3 - 5.5.1.1 - 5.5.1.2

Task 1b:  Listen to the podcast for an overview of this topic:

Task 2b: Make notes that:

• Define conservation of energy

• Define exothermic and endothermic reactions

• Give examples of exothermic and endothermic reactions

• Identify exothermic and endothermic reactions on basis of temperature change

• To investigate energy changes in chemical reactions

Task 3b: Make notes that:

• Identify the variables

•  Complete a risk assessment

• Copy and complete the results table

• Use the results to plot a graph

• Describe and explain the trend on your graph

Task 3c: Complete and mark the exam question 

Task 4b: Make notes that:

• Draw reaction profiles for exothermic and endothermic reactions including activation energy

• Define activation energy

• Identify endothermic and exothermic reactions from the reaction profile

• Set 1 & 2: Describe the energy changes when bonds are broken and made 

Set 2 go to task 5

Set 3 go to task 8 

Task 5b: Make notes that:

• Describe how the overall energy change in a reaction is affected by the balance between bond breaking in reactants and bond making in the products

• Calculate the energy transferred in chemical reactions

Task 5c: Complete and mark the exam questions 

Task 7b: Make notes that:

• Explain how a hydrogen fuel cell produces electricity.

• Give the advantages and disadvantages of hydrogen fuel cells.

• Describe the reactions in fuel cells using balanced symbol and half equations. 

• Evaluate the use of fuel cells and batteries to provide power for cars.  The data on the right should be used to help you.

Task 7c: Complete and mark the exam questions 

Task 8a: Watch the videos

Task 8b: Complete the seneca learning unit for your set. 

Task 9: Complete the quiz for your set to make sure you understand this unit.