C7 - Energy Changes 1️⃣✅

Question 1

What is an endothermic reaction?

Answer 1

An endothermic reaction is when energy is transferred from the surroundings during a reaction and the surroundings temperature falls

Question 2

What is an exothermic reaction?

Answer 2

An exothermic reaction is when energy is transferred to the surroundings during an reaction and the surroundings temperature rises

Question 3

What is a reaction profile?

Answer 3

A reaction profile is a graph that shows whether a reaction is exothermic or endothermic.

Question 4

What is activation energy?

Answer 4

Activation energy is the minimum amount of energy that particles must have to react when they collide.

Question 5

What does an endothermic reaction profile look like?

Answer 5

Question 6

What does an exothermic reaction profile look like?

Answer 6

Question 7

Breaking a bond requires ________ so is ____________

Answer 7

Breaking a bond requires energy so is endothermic

Question 8

Making a bond ________ energy so is ___________

Answer 8

Making a bond releases energy so is exothermic

Question 9

If a thermometer records an increase in temperature the reaction is ___________

Answer 9

exothermic

Question 10

If a thermometer records a decrease in temperature the reaction is ____________

Answer 10

endothermic

Question 11

In an endothermic reaction energy is transferred _______ the surroundings

Answer 11

In an endothermic reaction energy is transferred from the surroundings

Question 12

In an exothermic reaction energy is transferred _______ the surroundings

Answer 12

In an exothermic reaction energy is transferred to the surroundings

Question 13

What is bond energy?

Answer 13

The energy required to break a bond or the energy released when a bond is formed

Question 14

In terms of bond breaking and making, what is an exothermic reaction?

Answer 14

Less energy is required to break the bonds than is released when making the bonds

Question 15

In terms of bond breaking and making, what is an endothermic reaction?

Answer 15

More energy is required to break the bonds than is released when making the bonds

Question 16

What is the equation used when doing bond energy calculations?

Answer 16

change = break - make

Question 17

In bond energy calculations, if the change its negative it is ____________

Answer 17

Exothermic

Question 18

In bond energy calculations, if the change its positive it is ____________

Answer 18

Endothermic

Question 19

How do hydrogen fuel cells work?

Answer 19

1. Hydrogen fuel is supplied to the -ve anode and is oxidised electrochemically, loosing its electrons, and cosequrntly setting up a potential difference across the cell (diffeerence in charge across the 2 electrodes) and resulting in generating electricity
2. Hydrogen then becoms ions and travels through electrolyte to the +ve cathode where it and its electrons combine with oxygen to produce water.
3. For every 1 oxygen atom, 2 hydrogen and 2 electrons are required to produce a water molocule

Question 20

What is the half equation for the -ve anode in hydrogen fuel cells?

Answer 20

Question 21

What is the half equation for the +ve cathode in hydrogen fuel cells?

Answer 21

Question 22

What would the overall equation be to summarise a hydrogen fuel cell

Answer 22

REMEMBER: for evey 1 oxyen atom,2 hyrogen atoms is required to produce a water molocule hence for every 1 oxygen MOLOCULE you need 4 hydrogen atoms in order to produe a water molocule

Question 23

How do rechargable cells/ batteries work?

Answer 23

Rechargeable cells and batteries can be recharged because the chemical reactions are reversed when an external electrical current is supplied.

Question 24

How do non-rechargable batteries/ cells work?

Answer 24

In non-rechargeable cells and batteries the chemical reactions stop when one of the reactants has been used up

Question 25

What is an example of a non-rechargable battery?

Answer 25

Alkaline battery

Question 26

Electrodes in fuel cells are ____________ to electrodes in electrolysis

(give example)

Answer 26

Electrodes in fuel cells are opposite to electrodes in electrolysis
E.g.
Electrolysis: +ve anode & -ve cathode
Fuel cells: -ve anode & +ve cathode

Question 27

What are the pros and cons to hydrogen fuel cells?

Answer 27

Pros:
* Only require hydrogen & oxygen
* No waste produces produced
* Last longer than batteries & are less poluting to dispose of
Cons:
* Because hydrogen is a gas takes up alot of space to store
* The hydrogen is dangerous to store as its explosive when mixed with air
* To make the hydrogen fuel, energy from fossil fuel fuesl is required