Page 81 - Science Coursebook

5 End of unit questions

5.3 Some students carried out four reactions and took the temperatures at the start
and end of each reaction.

Reaction Start temperature / °C Final temperature / °C
A 20 25
B 19 16
C 20 23
D 18 24
a Which reactions are exothermic and which are endothermic? [4]
b Explain how you worked out your answer to a. [1]
c Which reaction had the largest energy change? [1]

5.4 Burning is a chemical reaction where heat energy is given out. It is an exothermic
reaction. Lisa has four fuels to investigate to find out which one gives out the most heat.

She uses apparatus like this.

thermometer

water

spirit burner
fuel in spirit
burner

a Which variable will Lisa change? [1]
b Name two variables Lisa must keep the same. [2]
c Explain what she must do in order to be able to identify which fuel gives out the
most energy. [2]
d Name one safety precaution she should take whilst carrying out this investigation. [1]

5 Energy changes 79