Topic 8 - Fuels and Earth Science

Question 1

What is a

chemical cell?

Answer 1

an electrochemical cell that produces a voltage across the cell until one of the reactants has been used up

Question 2

What is a

fuel cell?

Answer 2

a chemical cell that is supplied with a fuel and oxygen (or air) and uses the reaction between them to efficiently release energy

Question 3

What is the

overall reaction in a hydrogen-oxygen fuel cell?

Answer 3

hydrogen + oxygen -> water (+ energy)

Question 4

What are the advantages of

hydrogen fuel cells?

(6 advantages)

Answer 4

• they are much more efficient then power stations or batteries at producing electricity
• the electricity is generated directly from the reaction so fuel cells don’t require any heavy machinery
• as there aren’t a lot of stages to the process of generating electricity, there are fewer places for energy to be lost as heat
• unlike a car engine or a power station, there are no moving parts, so energy isn’t lost through friction
• doesn’t produce any conventional pollutants
• could be used to replace batteries which are incredibly polluting to dispose of because they are usually made of highly toxic metal compounds

Question 5

What are the disadvantages of

hydrogen fuel cells?

(4 disadvantages)

Answer 5

• hydrogen is a gas so it takes up far more space to store than liquid fuels like petrol
• hydrogen gas is very explosive so it is difficult to store safely
• the process of making hydrogen fuel is not environmentally friendly (either from hydrocarbons from fossil fuels or by electrolysing water which uses electricity which is normally generated by burning fossil fuels)
• it would be expensive to develop and install the necessary technology to use fuel cells widely