5.5.1.1 Energy transfer during exothermic and endothermic reactions

Law of conservation of energy states:

Energy cannot be created or destroyed.

Energy can only be transferred from one store to another.


Energy is conserved in any chemical reaction.


the amount of energy in universe

before the reaction takes place

=

the amount of energy in universe

at the end of a chemical reaction


In an exothermic reaction,

energy is transferred to the surroundings

so, the temperature of the surroundings  (thermometer) will increase.


Examples of exothermic reactions:



In an endothermic reaction,

energy is taken in from the surroundings

so, the temperature of the surroundings  (thermometer) will decrease.


Examples of endothermic reactions:




Q1. What is the law of conservation of energy?

Energy cannot be created or destroyed. 

Energy can only be transferred from one store to another.

Q2. What is an exothermic reaction?

A reaction where energy is transferred from the reaction to the surroundings.

Q3. What are two examples of exothermic reactions?

Combustion

Oxidation

Respiration

Neutralisation

Q4. What happens to the temperature of the surroundings during an exothermic reaction?

Increases

Q5. Give a real-life use of an exothermic reaction.

Handwarmers, self-heating cans

Q6. What is an endothermic reaction?

A reaction where energy is transferred from the surroundings into the reaction.

Q7. What are two examples of endothermic reactions?

Thermal decomposition reactions

Citric acid and sodium hydrogen carbonate

Ammonium nitrate + water

Q8. What happens to the temperature of the surroundings during an endothermic reaction?

Decreases

Q9. Give one real life use of an endothermic reaction. 

Sports injury cool packs

Q10. Is respiration an exothermic or endothermic reaction?

Exothermic

Q11. Is photosynthesis an exothermic or endothermic reaction?

Endothermic