C5 - Energy Changes

Question 1

What are the 2 types of chemical reaction and how are they different?

Answer 1

Exothermic:
- Gives out energy
- Warms the surroundings

Endothermic:
- Takes in energy
- Makes the surroundings cold

Question 2

What does the reaction profile of an exothermic reaction look like?

Answer 2

The overall energy would decrease:

Energy
|
| ___
| / \
| ______/ \
|reactants \_______
| products
|____________________________→ Time

Question 3

What does the reaction profile of an endothermic reaction look like?

Answer 3

Overall energy would increase:

Energy
| _____
| / \
| / \_______
| / products
| ______/
|reactants
|____________________________→ Time

Question 4

What is the activation energy?

Answer 4

The activation energy is the minimum energy needed for a reaction to take place.

Question 5

What are the uses of exothermic
reactions?

Answer 5

1 – Heating
2 – Hand warmers
3 – Self-heating cans

Question 6

What are the uses of endothermic reactions?

Answer 6

1 – cold packs
2 – drink coolers

Question 7

Does making chemical bonds give out energy to the surroundings or take in energy from the surroundings?

Answer 7

Making bonds releases energy to the surroundings.

Question 8

What is the equation to calculate the overall energy change in a chemical reaction?

Answer 8

Overall energy change is the energy needed to break the bonds minus the energy released when new bonds form.
OR
Energy change = energy in – energy out

Question 9

What is the difinition of bond energy?

Answer 9

The energy required to break a specific chemical bond.