C5: Energy changes

Question 1

Endothermic reactions(3):

Answer 1

Takes in energy from surroundings;

Thermal decomposition, sports injury packs

Question 2

Exothermic reactions(3):

Answer 2

Reactions that releases energy to the surroundings(temp increases in surroundings);
Combustion, hand warmers

Question 3

Energy level diagrams(3):

Answer 3

Shows the amount of energy lost and gained during a reaction

• endothermic: products are higher than reactants because thy take in energy from surroundings
• exothermic: products are lower as they release energy to surroundings

Question 4

Hydrogen fuel cells(5):

Answer 4

Hydrogen + oxygen = water
\+ no pollutants
\+ can be a range of sizes
- hydrogen is highly flammable
- hydrogen is difficult to store

Question 5

Hydrogen fuel cell equations(2):

Answer 5

Cathode:
2H2 + 4OH- = 4H2O + 4e-

Anode:
O2 + 2H2O + 4e- = 4OH-

Question 6

Define activation energy

Answer 6

The minimum amount of energy that colliding particles require in order to react

Question 7

What is the difference between a battery and a cell?(4)

Answer 7

Cell= 1 can be made by connecting 2 different metals in contact with an electrolyte

Battery= 2+ cells connected in series to provide a greater voltage

Question 8

Rechargeable cells

Answer 8

They can be recharged because the reactions are reversible when an electric current is supplied

Question 9

Non- rechargeable batteries

Answer 9

They CANNOT be recharged because one of the reactants is used up