Grade 7 · Science · Unit 15 of 16
Energy Changes
Melting points, energy exchanges and efficiency
What your child practises
Children practise why substances melt and boil at different temperatures, follow energy as it changes form, and learn why some energy always ends up as heat.
Manitoba Curriculum learning outcome: SCI.7.E.3, SCI.7.E.10, SCI.7.E.11 · melting and boiling points, energy exchanges in everyday phenomena, and energy transfer, dissipation as heat and efficiency
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
At what temperature does pure water melt (or ice melt)?
- 32 °C
- -10 °C
- 100 °C
- 0 °C
Show answer
0 °C
Hint: 0 °C is the melting point of ice.
Question 2
When you eat food and run, the energy changes from…
- sound to electrical
- chemical energy in food to motion and heat
- nuclear to magnetic
- light to chemical
Show answer
chemical energy in food to motion and heat
Hint: Your body releases stored energy.
Question 3
Plants use sunlight to make food. This is an energy exchange from…
- light energy to chemical energy
- sound to light
- electrical to magnetic
- heat to sound
Show answer
light energy to chemical energy
Hint: Photosynthesis stores energy.
Question 4
Which device changes electrical energy mainly to heat?
- a microphone
- a speaker
- a camera
- a toaster
Show answer
a toaster
Hint: Heating elements make heat.
Question 5
Efficiency tells us…
- how much of the energy put in is used for the job we want
- what colour a device is
- how heavy a device is
- how loud a device is
Show answer
how much of the energy put in is used for the job we want
Hint: More useful output means higher efficiency.
Question 6
The energy stored in a hydroelectric reservoir is…
- sound energy
- chemical energy in coal
- gravitational potential energy of water
- heat from nuclear fuel
Show answer
gravitational potential energy of water
Hint: Water high above the turbine has stored energy.