1. Questions on Combustion KEYWORDS: Exothermic, Endothermic,
Endothermic Reactions
Starter
Questions on Combustion
Give an example of a combustion reaction?
What type of reaction is this exothermic or endothermic?
Explain why this reaction releases energy?
Suggest why these reactions changed the world?
Today you will be learning about endothermic reactions and their uses.
KEYWORDS: Exothermic, Endothermic,
Energy level Profile

2. Learning Outcomes
Grade 4– Describe the difference between exothermic and endothermic reactions. 
Grade 6 – Explain how energy change from a chemical reaction can be used. 
Grade 8 – Evaluate uses and applications of exothermic and endothermic reactions given appropriate information.

3. Homework
Homework: Students should research self-heating cans and find out the risks of using them to heat food.
Complete by the next lesson.

4. Exothermic Reactions
An exothermic reaction is one that transfers energy FROM the reacting chemicals TO the surroundings.
More simply, it’s a reaction that gives off heat
LO: Understand exothermic and endothermic reactions

5. Exothermic Examples Burning fuels Neutralisation Respiration
LO: Understand exothermic and endothermic reactions

6. Endothermic Reactions
An endothermic reaction is one that TAKES IN energy from the surroundings.
These reactions are a lot less common than exothermic reactions
LO: Understand exothermic and endothermic reactions

7. Practical – Endothermic reaction
Aim: To investigate the temperature
change during an endothermic reaction
Method:
Measure out 20cm³ of citric acid and place in a conical flask
Measure the initial temperature of the acid
Add three spatulas of sodium hydrogencarbonate and stir
Measure the temperature every 30s for 4 minutes 
LO: Understand exothermic and endothermic reactions

8. Practical – Endothermic reaction
Make a conclusion for how you know the reaction was an endothermic reaction. Use results from your experiment to back up your conclusion
LO: Understand exothermic and endothermic reactions

9. Self Heating Cans List all of the Cans key features
What is the chemical reaction?
Write the word equation?
Write the symbol equation?
How do you start the reaction?
How do you know the reaction is done?
How can heat be distributed evenly?
Self Heating Cans

10. Hand warmers and self heating cans
Reusable
Sodium ethanoate solution is dissolved in water, until no more will dissolve.
A small disc in the warmer is pressed, this scratches the metal and small metal particles are scraped off.
These metal particles “seed” the crystallisation.
This reaction gives off energy as heat.
Boiling will reverse the change so it can be reused
Single use
Iron oxidises to form iron (III) oxide.
This reaction releases energy as heat.
Sodium chloride is used as a catalyst to speed up the reaction.
These types of hand warmers last a long time but they cannot be used again.

11. List pros and cons of each type of hand warmer

12. KNOWLEDGE CHECK
State what is meant by an exothermic and endothermic reaction
Start Timer 7
10 Minutes 10 8
Give two examples of exothermic reactions 8 6 4
Explain how chemical hand warmers work 9 2