Lesson 1: Endo/ Exo reactions

Question 1

True or False

When an exothermic reaction takes place, there is more energy in the universe than before the reaction.

Answer 1

• False.
• The amount of energy in the universe at the end of a chemical reaction is the same as before the reaction takes place.

Question 2

What is an exothermic reaction?

Answer 2

• An exothermic reaction is one that transfers energy to the surroundings - so temp of surroundings increases.

Question 3

Give 3 broad types of exothermic reactions.

Answer 3

1.) Combustion
2.) Many oxidation reactions
3.) Neutralisation

Question 4

Give 2 examples of everyday uses of exothermic reactions.

Answer 4

1.) Self- heating cans
2.) Hand warmers.

Question 5

Describe the energy of products vs reactants in exothermic reaction.

Answer 5

• Product molecules have less energy than reactant molecules.
• As energy has been transferred to the surroundings.

Question 6

What is an endothermic reaction?

Answer 6

• An endothermic reaction is one that takes in energy from the surroundings - so the temperature of the surroundings decreases.

Question 7

Give 3 examples of endothermic reactions.

Answer 7

1.) Thermal decomposition
2.) Reaction of citric acid and sodium hydrogencarbonate.
3.) Some sport injury packs are based on endothermic reactions.

Question 8

What is collision theory?

Answer 8

• In order for a reaction to take place, particles must collide with each other with sufficient energy.

Question 9

What is the activation energy?

Answer 9

The minimum amount of energy that particles must have to react is called the activation energy.