Primary 3 · Science · Physical sciences
Heat on the move
Students explore how heat moves from warmer objects to cooler ones and identify sources of heat, such as the Sun, fires and rubbing hands together.
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These lessons were written around Australian Curriculum strands and matched to Singapore levels by age (Primary 1 is the first year of primary school). They are not aligned to MOE syllabuses or the PSLE, so check them against the syllabus your child is working towards.
Learning goals
Learners will
- Identify sources of heat, such as the Sun, fires, electric heaters and rubbing hands together.
- Explain that heat moves from warmer objects to cooler objects.
- Compare how quickly heat moves through different materials.
Success looks like
- I can name four sources of heat.
- I can explain why a hot drink cools down and an ice cube melts in my hand.
- I can say whether metal, wood or plastic lets heat through fastest.
The big idea
Heat is a kind of energy. It always moves from something warmer to something cooler, until they are the same temperature.
A heat source gives out heat. Examples:
- The Sun, our biggest heat source. It warms the land, the sea and the air.
- Fire, such as a campfire, candle or gas stove.
- Electricity, in heaters, toasters, ovens and hair dryers.
- Rubbing things together. Rub your hands together quickly and they get warm.
- Living things. Our bodies make heat, which is why a room full of people warms up.
A hot drink left on the table cools down because heat moves from the drink into the cooler air and cup. An ice cube melts in your hand because heat moves from your warm hand into the ice. Your hand feels cold because it is losing heat.
Some materials let heat through quickly. These are conductors, like metal. That is why a metal spoon in a hot drink soon feels hot.
Other materials slow heat down. These are insulators, like wood, plastic, wool and air. Saucepan handles are often plastic or wood, and a woollen jumper keeps you warm by trapping your body heat, not by making heat.
We measure how hot or cold something is with a thermometer. Temperature is measured in degrees Celsius (°C).
Worked examples
Spoon race
Which spoon lets heat travel up it fastest: metal, plastic or wood?
- Stick a bean to the top of each handle with an equal dab of butter.
- An adult stands all three spoons in the mug of hot tap water at the same time.
- Watch which bean slides off first as the butter melts.
- The bean on the metal spoon falls first. The others take much longer, or do not fall at all.
Answer: Metal, because it is a good conductor of heat. Wood and plastic are insulators.
Ice in your hand
Why does an ice cube melt when you hold it, and why does your hand feel cold?
- Your hand is warmer than the ice.
- Heat moves from the warmer hand into the cooler ice.
- The ice gains heat and melts; your hand loses heat and feels cold.
Answer: Heat moves from your hand to the ice. Cold does not move into your hand; heat moves out of it.
A cooling cup
A cup of water was 70 °C. Twenty minutes later it was 50 °C. How much did it cool, and why?
- Subtract: 70 − 50 = 20.
- It cooled by 20 degrees.
- Heat moved from the warm water into the cooler air around it.
Answer: It cooled by 20 °C because heat moved into the cooler surroundings.
Practice check
Have a go, then check your answers. Each answer comes with an explanation.
Answer guide for parents
Which way does heat move?
From warmer to cooler things — Heat always moves from warmer things to cooler things.
Which is a heat source?
The Sun — The Sun gives out heat.
What happens to a hot drink left on the table?
It cools until it is about the same temperature as the room — Heat moves out of the drink into the cooler room.
Which spoon will feel hot first when it stands in a hot drink?
A metal spoon — Metal is a good conductor, so heat moves through it quickly.
How does a woollen jumper keep you warm?
It traps your body heat — Wool is an insulator. It slows down heat leaving your body.
Rub your hands together quickly. Do they get warmer or cooler?
warmer — Rubbing makes heat, so your hands get warmer.
A bowl of soup cools from 70 °C to 50 °C. By how many degrees did it cool?
20 — 70 − 50 = 20 degrees.
What tool do we use to measure temperature?
thermometer — A thermometer measures temperature.
Watch out for
- Many students think 'cold' moves into things. Really, heat moves out of warmer things into cooler things.
- Students often think jumpers and blankets make heat. They are insulators that trap the heat our bodies make.
- Students may think metal is colder than wood in the same room. Both are the same temperature, but metal conducts heat away from your hand faster, so it feels colder.
Tips for parents
- Use hot tap water, not boiling water, and have an adult pour it and place the spoons.
- Point out heat moving in daily life: steam from a cup, butter softening on warm toast, a cold drink warming up.
- Safety: an adult handles all hot water, stoves and heaters; children never use matches, candles or fires.
Go further
- Wrap one ice cube in a woollen sock and leave another uncovered. Predict and check which melts first.
- Feel a metal tray and a wooden board that have been in the same room, then talk about why they feel different.
- Use a thermometer to measure the temperature of a cup of warm water every 5 minutes and record the results.
About 45 minutes
You'll need
- A metal spoon, a plastic spoon and a wooden spoon of similar length
- A mug of hot tap water (an adult pours it)
- Three small, equal dabs of butter and three dried beans or sequins
- Ice cubes and a plate
- A kitchen thermometer if you have one
Key words
- heat
- A form of energy that moves from warmer things to cooler things.
- temperature
- How hot or cold something is, measured in degrees Celsius (°C).
- heat source
- Something that gives out heat, such as the Sun, a fire or a heater.
- thermometer
- A tool for measuring temperature.
- conductor
- A material that lets heat move through it easily, such as metal.
- insulator
- A material that slows down heat moving through it, such as wood, plastic, wool or air.
Still tricky?
For parents
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