Energy

Question 1

What is an endothermic reaction?

Answer 1

A reaction in which energy is taken from the surroundings (absorbs energy)

Question 2

Recognise exothermic and endothermic reactions using temperature changes

Answer 2

• A rise in temperature is known as an exothermic reaction as heat energy is given out to the surroundings.
• A fall in temperature is known as an endothermic reaction as heat energy is taken in from the surroundings

Question 3

Describe using a diagram a simple calorimetric method for comparing the energy transferred per gram of fuel combusted

Answer 3

Use of spirit burner or a bottled gas burner
Heating water in a copper calorimeter
Measuring the temperature change
Fair and valid tests

Question 4

What reaction do bonds break?

Answer 4

Endothermic

Question 5

What reaction are bonds made?

Answer 5

Exothermic

Question 6

Equation for energy per gram

Answer 6

Energy per gram= energy released (in J) / mass of fuel burnt

Question 7

Equation for energy transferred

Answer 7

Energy transferred= m x c x ∆T

m = mass of water heated
c = specific heat capacity (4.2J/g°C)
∆T = temperature change

Question 8

Explain why a reaction is exothermic or endothermic using the energy changes that occur during bond breaking

Answer 8

• Chemical reaction that require more energy to break bonds than is released when new bonds are made are endothermic reactions
• Chemical reactions that release more energy when bonds are made than is required to break bonds are exothermic reactions

Question 9

What is an exothermic reaction?

Answer 9

A reaction in which energy is transferred into the surroundings (releases energy)