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SavannahYear 8
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ScienceEnergy and waves26 min★★ difficulty

Conservation of energy

Energy cannot be created or destroyed — only transferred from one store to another, or usefully to wastefully. The total always stays the same.

Part of your national curriculum
  • Physics: energy: Understand energy as a quantity that can be quantified and calculated, and the total energy has the same value before and after a change

Lesson overview

What you'll learn in this lesson

Understand energy as a quantity that can be quantified and calculated, and the total energy has the same value before and after a change

Key learning points

  • • Energy stores and transfers
  • • Conservation of energy
  • • Worked example

This lesson at a glance

  • 26 minutes
  • 14 parts to scroll through
  • 3 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

energyquantityquantifiedcalculatedbefore

Scroll down — the lesson carries on below

Part 1 of 14 · Discover7%
1

Watch & discover

Part 1 of 14

Watch first

Conservation of energy

An English teaching video on this topic from Lammas Science. Watch it, then scroll down for the lesson.

In a nutshell

Understand energy as a quantity that can be quantified and calculated, and the total energy has the same value before and after a change

2

Learning cycle

Part 2 of 14

Learning cycle 1 of 2

Part 1 · Energy stores and transfers

A short piece of teaching, then a check to make sure it has landed.

3

Explore the idea

Part 3 of 14

Learn

Energy stores and transfers

Energy can be stored in different ways: kinetic (moving objects), gravitational potential (raised objects), chemical (food, fuel), thermal, and elastic. A change, such as dropping a ball, transfers energy between these stores, for example from gravitational potential to kinetic.

4

Explore the idea

Part 4 of 14

Learn

Conservation of energy

The law of conservation of energy states that energy cannot be created or destroyed, only transferred, stored or dissipated in different ways. The total energy before a change always equals the total energy after it, even though some is often wasted as heat.

5

Quick check

Part 5 of 14

Quick check

What does the law of conservation of energy state?

6

Reset break

Part 6 of 14

Pause

That's sitting 1 of 2 done

Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.

Stop here for now
7

Quick check

Part 7 of 14

Quick check

A falling object's gravitational potential energy mainly transfers into which store as it falls?

8

Learning cycle

Part 8 of 14

Learning cycle 2 of 2

Part 2 · Worked example

A short piece of teaching, then a check to make sure it has landed.

9

Explore the idea

Part 9 of 14

Learn

Worked example

A ball with 20 J of gravitational potential energy is dropped. Just before hitting the ground (ignoring air resistance), all 20 J has transferred to kinetic energy. In reality, a little energy is also transferred to the surroundings as heat and sound due to air resistance, but the total is still 20 J.

10

Quick check

Part 10 of 14

Quick check

If a raised ball has 50 J of gravitational potential energy, what is the total energy just before landing (ignoring air resistance)?

11

Challenge round

Part 11 of 14

Game · Sort it

Which of these are true?

Drag each card into the right column. Tap a card first if dragging is fiddly.

True

Not true

12

Challenge round

Part 12 of 14

Game · Fill the gaps

Finish the sentences

Choose the word that belongs in each gap.

____ can be stored in different ways: kinetic (moving objects), gravitational potential (raised objects), chemical (food, fuel), thermal, and elastic.

The total energy ____ a change always equals the total energy after it, even though some is often wasted as heat.

13

Mastery quiz

Part 13 of 14

Marked quiz

End of lesson quiz: Conservation of energy

3 questions, marked with the reasoning shown. No timer.

  1. 1. What does the law of conservation of energy state?

  2. 2. A falling object's gravitational potential energy mainly transfers into which store as it falls?

  3. 3. If a raised ball has 50 J of gravitational potential energy, what is the total energy just before landing (ignoring air resistance)?

14

Lesson round-up

Part 14 of 14

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 3 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Case study

Why the school greenhouse failed

A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.

The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.

The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.

Written for Good Learning Co.

Reading questions

  1. Name the variable the club changed the second time, and one variable they kept the same.
  2. Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
  3. Write a conclusion for the club's report, saying how far the evidence supports it.

  • Method and results

    Writing

    Write the aim, what you changed, what you measured and what you kept the same, then record your results in a table.

    1 page + results table

  • Conclusion

    Writing

    Explain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.

    6–8 sentences

  • Labelled diagram

    Diagram

    Draw the apparatus or the process in pencil, label it fully, and photograph it.

    1 labelled diagram

  • Reading and notes

    Reading

    Read the lesson text again and write the key ideas in your own words.

    Half a page of notes

Saved as you type.

Part 1 of 14 · Watch & discover

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    Understand energy as a quantity that can be quantified and calculated, and the total energy has the same value before and after a change

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