Year 9 Science · Unit 3 · Lesson 24
Foundation Worksheet
Learning Goals
Fill the gap: key words from the unit
Choose the correct word from the word bank. Each word is used once. Two words will not be used.
The law of of energy states that energy cannot be created or destroyed; it can only be transferred or transformed. When heat travels through a solid without the material itself moving, the process is called . Solar and wind energy are energy sources because they are replaced naturally. In a house, appliances are wired in so each one receives the same of 230 volts. Green is made using renewable electricity to split water. Australia’s CO₂ per person are among the highest in the world. The of a device is its useful energy output divided by its total energy input.
1. Name the three ways heat can be transferred, and give one example of each from a home.
Sort it: which part of the unit?
Write each idea in the correct column. Each column gets three ideas.
Heat transfer
Making and storing electricity
Circuits
Energy data and audits
2. A 12 V aquarium pump draws a current of 0.50 A, and it runs all day and all night. Use P = V × I to find its power. Then use E = P × t to find the energy it uses in one day (86,400 s), in joules and in kWh.
Power W
Per day J
Daily kWh
Investigation: three garden tools
A class worked out the energy going into three garden tools during one minute of use, from the fuel or electricity each one used. They also worked out how much of it became useful kinetic energy of the moving parts.
| Tool | Energy in (J) | Useful energy out (J) |
|---|---|---|
| Battery hedge trimmer | 9,000 | 6,300 |
| Petrol leaf blower | 60,000 | 12,000 |
| Electric pressure washer | 90,000 | 54,000 |
Source: sample class results.
3. Calculate the efficiency of each tool.
Hedge trimmer %
Leaf blower %
Pressure washer %
4. How much energy does the leaf blower waste in one minute, and into which forms of energy does it go?
Wasted J
5. The pressure washer wastes 36,000 J every minute, far more than the hedge trimmer takes in, yet it is not the least efficient tool. Explain how this can be true.
Scenario: from gas to a moving train
A gas-fired power station burns natural gas to boil water into steam. The steam spins a turbine joined to a generator. The electricity travels along high-voltage transmission lines to Sydney, where it drives the motors of an electric train.
6. Trace the energy from the natural gas to the moving train. Name each energy transformation and transfer, say where energy is wasted, and use the law of conservation of energy to explain why the train gets much less energy than the gas released.