C7 Energy Changes Flashcards
How is electricity made in batteries?
By placing 2 different metals in an electrolyte solution
What is an electrolyte solution?
A solution that can conduct electricity, e.g. a molten ionic compound
On what condition can cells produce electricity?
If they use metals with different reacitivity
How can the potential difference be changed in a cell?
By increasing/decreasing the difference in reactivity between the metals, you increase/decrease the potential difference.
Also the electrolyte can affect the potential difference
What is a battery?
2 or more cells connected in series to produce a greater voltage
Why can rechargable batteries be recharged?
The chemical reactions can be reversed when applying an electrical current
How do fuel cells produce electricity?
A fuel e.g. hydrogen is reacted with pure oxygen or air
What waste product is produced in a hydrogen fuel cell?
Water
What’s the half equation at the negative electrode in a hydrogen fuel cell?
2H₂ —- 4H⁺ + 4e⁻
What’s the half equation at the positive electrode in a hydrogen fuel cell?
2O2⁻ → O2 + 4e-
What is happening to the hydrogen inside the hydrogen fuel cell?
It’s being oxidised (gaining oxygen)
What is the overall equation inside a hydrogen fuel cell?
O₂ + 2H₂ —– 2H₂O
What are some advantages of Hydrogen fuel cells compared to rechargable batteries?
- They produce energy as long as hydrogen is present
- They don’t get less efficient the longer they run
- Can be used as a source of drinking water
- Can be used to replace fossil fuels as they don’t
release greenhouse gases
What are some disadvantages of rechargable batteries compared to hydrogen fuel cells?
- They run out and need to be recharged
- They store less electricity the more charging cycles they go through and eventually need to be replaced
What are some disadvantages of Hydrogen fuel cells compared to rechargable batteries?
- Hydrogen is an explosive gas and is difficult to store
- They produce a relatively low voltage
What are some advantages of rechargable batteries compared to Hydrogen fuel cells?
- They can produce a larger voltage
- No dangerous fuels are required for them
Explain how Hydrogen fuel cells produce electricity
As fuel enters the cell, it become oxidised, setting up a potential difference across the cell
Hydrogen fuel cells can be used to power different forms of transport.
Some diesel trains are being converted to run on hydrogen fuel cells.
A newspaper article referred to the converted trains as the new ‘steam trains’.
Suggest why.
- In a fuel cell hydrogen is
oxidised and water is produced
Hydrogen fuel cells can be used to power different forms of transport.
Some diesel trains are being converted to run on hydrogen fuel cells.
A newspaper article referred to the converted trains as the new ‘steam trains’.
Suggest why.
- In a fuel cell hydrogen is
oxidised and water is produced
