Energy transfers in reactions

Question 1

Where is energy transferred to in exothermic reactions?

Answer 1

To the surroundings (EXit - Going out)

Question 2

What happens in ‘chemical energy —–> thermal energy’?

Answer 2

Thermal energy is released to the surroundings

Question 3

What happens in ‘thermal energy —–> chemical energy’?

Answer 3

Thermal energy is taken in from the surroundings

Question 4

What happens to the temperature in exothermic reactions?

Answer 4

It increases

Question 5

Examples of exothermic reactions?

Answer 5

Combustion reactions, neutralisation reactions, reactions of acids with metals, hand warmers

Question 6

Where is energy transferred to in endothermic reactions?

Answer 6

From the surroundings (ENtrance - Going in)

Question 7

What happens to the temperature in endothermic reactions?

Answer 7

Can decrease or may need heat to be added for the reaction to proceed

Question 8

Examples of endothermic reactions?

Answer 8

Thermal decomposition reaction, photosynthesis, cooling packs

Question 9

What is activation energy?

Answer 9

The amount of energy needed to start a reaction

Question 10

What does activation energy make the particles in the reaction do?

Answer 10

Collide with each other so they can react

Question 11

In exothermic reactions, the product of the reaction have a ___________ energy level than the reactants

Answer 11

Lower

Question 12

Which reaction has a positive energy transferred number and which one has a negative number?

Answer 12

Exothermic - Negative
Endothermic - Positive

Question 13

In endothermic reactions, the product of the reaction have a ___________ energy level than the reactants

Answer 13

Higher

Question 14

What is energy transferred measured in?

Answer 14

kJ/mol

Question 15

How to work out overall energy change?

Answer 15

Products energy - reactants energy

Question 16

How to work out total energy change in a reaction?

Answer 16

Energy taken in when bonds are broken - Energy given out when new bonds are formed

Question 17

What is bond energy?

Answer 17

The amount of energy required to make or break a bond

Question 18

Negative result = _____

Answer 18

Exothermic reaction

Question 19

Positive result = _____

Answer 19

Endothermic reaction

Question 20

What is a cell?

Answer 20

A single power cell, two different metals in contact through an electrode, contains chemicals which react to produce electricity

Question 21

What is a battery?

Answer 21

Two or more cells connected in series, produce a higher voltage than a cell

Question 22

Pros of fuel cells (hydrogen)?

Answer 22

Only product is water, continuous supply of energy if the fuel doesn’t run out, very efficient and little energy is wasted as heat

Question 23

Cons of fuel cells (hydrogen)?

Answer 23

Hydrogen is extremely flammable, hydrogen might be produced using fossil fuels or in a reaction that produces co2, very expensive to make, hydrogen needs to be stored in pressurised containers which could easily explode