Unit 5- Energy Changes Flashcards

(15 cards)

1
Q

What is an Exothermic reaction

A

One which transfers energy to the surroundings usually by heating. This is shown as a rise in temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is an endothermic reaction

A

Reactions which takes energy in from the surroundings, this is shown as a fall in temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Example of Exothermic reaction

A

Neutralisation, combustion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Uses of Exothermic reactions

A

Hand warmers- use the Exothermic oxidation of iron in air to release energy
Self heating cans

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Example of endothermic reaction

A

Thermal decomposition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Uses of endothermic reactions

A

Used in sport injury packs, allows pack to become instantly cooler without having to be put in freezer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a fuel cell

A

Electrical cell that produces electricity using fuel and oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Uses of fuel cells

A

Used in vehicles- don’t produce nasty pollutants, however uses a lot of energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the voltage in a cell dependant on

A

Type of electrode and electrolyte

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Advantages and disadvantages of hydrogen fuel cells

A

Produce electricity as long as they are supplied with fuel (hydrogen) inline batteries that will eventually run out
Only by product is water
Clean alternative (environmentally friendly)

More expensive
Hydrogen flammable so careful handling and storage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Advantages + disadvantages of rechargeable cells (batteries)

A

-ideal for portable devices
-Less expsive than hydrogen fuel cell
-Easy to use

-limited range need to be reachrged
-environmental impacts when disposing of

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

At the anode hydrogen fuel cells half equation - remember anode is the negative electrode in hydrogen fuel cells

A

Oxidation of hydrogen :
2H2 —> 4H+ + 4e

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How hydrogen fuel cells work

A
  1. Hydrogen comes in from the leftoutlet and is oxidised by the anode
  2. Hydrogen atom loses an e,et rom to be come H+ ions
  3. Hydrogen ions move over the electrolyte to the cathode
  4. They then react to make water (reduced)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

At the cathode hydrogen fuel cells half equations- remember the cathode is positive as it is the other way around

A

O2 + 4H+ +4e- —> 2H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Overall hydrogen fuel cell equation

A

2H2 + O2 —> 2H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly