Heat moves — Physical education, 7–10 years
Heat moves from something warmer to something cooler. This explains why a hot drink cools in a room and why a fridge can keep food cold.
Heat spreads out
Heat is energy moving between things because their temperatures are different. It naturally travels from the warmer thing towards the cooler thing until their temperatures become closer. A cold spoon in hot soup warms up because heat leaves the soup and enters the spoon.
Why people learned this
People wanted to keep food warm or cold, and to avoid burning their hands. That problem led to choices such as metal for a pan, wood or plastic for a handle, and layers of clothing for the body. The useful question is not just “Is it hot?” but “Where can the heat go?”
A cup cooling
A cup of tea is at 80°C and the room is at 20°C. First, heat moves from the tea into the cup and the surrounding air. As the tea cools, the difference becomes smaller, so the heat transfer slows. It may eventually reach about 20°C, not because cold enters it, but because heat leaves it.
The common mistake
People often say that “cold travels into” a warm object. That sounds sensible because a drink gets cold, and we feel cold air around it. In physical terms, heat is leaving the drink and moving to cooler surroundings; “cold” describes having less thermal energy, rather than being a substance flowing in.
Where we use it
An oven mitt slows heat moving from a hot tray to your hand. A thermos uses several barriers to slow heat moving in or out, so soup stays warm and water stays cool. Houses also use insulation in roofs and walls to make heating and cooling more effective.
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