7 - Energy changes Flashcards
1
Q
What are some examples of exothermic reactions?
A
- Combustion
- Neutralisation
2
Q
What is an example of an endothermic reaction?
A
- Thermal decomposition
3
Q
How can we make chemical cells & batteries?
A
- Dip two metal rods into an electrolyte solution
- The more reactive metal donates electrons, causing a flow of electrical current
- The greater the difference in reactivity, the greater the voltage
4
Q
Which cells cannot be recharged?
A
- Primary battery cells
- Dry cells
- Alkaline cells
5
Q
What are the cons of BURNING hydrogen as a fuel?
A
- Safety
- Storage & transportation
- Obtaining hydrogen by electrolysis burns fossil fuels
6
Q
How do hydrogen fuel cells work?
A
- Hydrogen reacts with oxygen and loses electrons to make water
- Oxygen picks up the electrons
- Flow of electrons carries currents
7
Q
What are the advantages of hydrogen fuel cells?
A
- Don’t need to be electrically recharged
- No pollutants
- Come in a range of sizes
8
Q
What are the disadvantages of hydrogen fuel cells?
A
- Hydrogen is flammable
- Hydrogen is obtained using non-renewable resources
- Hydrogen is difficult to store
