Science lesson plan · 9th grade (Year 10 in England) · 45 minutes
Efficiency
Energy
CCSS NGSS.HS-PS3-3England: KS4 Combined Science: Energy
Objective and success criteria
Students will: Efficiency.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Conservation of energy and wasted energy
Leads to: the next skill in this area.
Materials: Wind-up toys or a pendulum, Energy transfer diagrams, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).
Warm-up · 5 min
- Quick retrieval from earlier learning (Conservation of energy and wasted energy). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- A speaker is supplied with 1200 J of energy. It transfers 240 J usefully. How much energy is wasted, in J? → 960 JPrompt: Energy is conserved: input = useful output + wasted output.
- How can wasted energy in a machine with moving parts be reduced? (remove the oil / lubricate the parts to reduce friction / make it move faster / paint it a darker colour) → lubricate the parts to reduce frictionPrompt: What causes heating where parts rub?
- Conservation of energy: which statement is NOT true? (Energy is used up and disappears. / Wasted energy is often transferred to the surroundings by heating. / A Sankey diagram shows useful and wasted energy. / The total energy in a closed system stays the same.) → Energy is used up and disappears.Prompt: Can energy ever be created or destroyed?
Hook · 5 min
- Wind up a toy or stretch an elastic band and ask where the energy goes.
- Share the objective: Efficiency. Read the success criteria together.
I do: model it · 10 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: A device is supplied with 200 J and transfers 30 J usefully. What is its efficiency, as a percentage?
- Step 1: 30 ÷ 200 × 100 = 15
- Step 2: So the answer is: 15%
- Answer: 15 %
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 10 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- A device is supplied with 800 J and transfers 720 J usefully. What is its efficiency, as a percentage? → 90 %Prompt: efficiency = useful output ÷ total input
- A motor is 40% efficient. It is supplied with 3000 J. How much useful energy does it transfer, in J? → 1200 JPrompt: useful output = efficiency × total input
You do: independent practice · 10 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- A motor is 20% efficient. It is supplied with 2000 J. How much useful energy does it transfer, in J? → 400 JPrompt: useful output = efficiency × total input
- An electric motor is 80% efficient. What happens to the other 20%? (It is turned into extra motion / It is destroyed / It is mostly wasted heating the motor and its surroundings / It is stored in the plug) → It is mostly wasted heating the motor and its surroundingsPrompt: Energy is conserved.
Watch out for
- Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
- Remembering facts without the reason: ask "why?" and "what is the evidence?"
Support and stretch
Support
- Review first: Conservation of energy and wasted energy.
- Use concrete materials: wind-up toys or a pendulum.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-9.
Free lesson plan from eurekami.com/lesson-plan-builder