C5 - Energy Changes Flashcards
1
Q
Are exothermic energy changes shown as positive or negative ?
A
Negative
2
Q
Are endothermic energy changes shown as positive or negative ?
A
Positive
3
Q
Is bond breaking endothermic or exothermic ?
A
Endothermic
4
Q
Is bond making endothermic or exothermic ?
A
Exothermic
5
Q
What are the benefits of hydrogen fuel cells ?
A
- Produce electricity, for as long as you provide hydrogen
- They don’t get less efficient the longer they run
- Can be the source of drinkable water
6
Q
What are the problems of hydrogen fuel cells ?
A
- explosive gas and is difficult to store
- produce a low voltage, many are needed together
7
Q
What are the benefits of rechargeable batteries?
A
- no dangerous fuels are required
- produce a greater voltage than hydrogen fuel cells
8
Q
What are the problems of rechargeable batteries ?
A
- run out and need to be recharged
- store less electricity, more charging cycles they go through, so they have to be replaced eventually
9
Q
What are exothermic reactions used for ?
A
- hand warmers
- self - heating cans
