Heat flows from warmer to cooler — Physical education, 11–13 years
Temperature tells how hot or cold something is, while heat is energy moving between objects. Without a machine doing extra work, heat spreads from warmer places towards cooler ones.
Thermal energy spreads
When a warmer object touches a cooler one, particles in the warmer object transfer energy through the contact. The warmer object loses some energy and the cooler one gains it. This transfer is called heat, and it continues until their temperatures become equal.
Why explain heat flow?
People wanted to predict how food cools, how homes lose warmth and how engines handle hot parts. A temperature tells the state of one object, but it does not show the direction of energy movement. The idea of heat flow gives that direction and helps compare materials.
A cool drink in warm air
A can is at 5 °C and the room is at 22 °C. The room air is warmer, so energy moves from the air into the can. The drink’s temperature rises while the nearby air cools slightly. Eventually both approach the same temperature, unless a fridge removes energy.
Cold does not flow
People often say that cold moves from an ice cube into a drink. This is reasonable because the drink gets colder, but what actually moves is energy: it leaves the drink and enters the ice. “Cold” describes a lower temperature; it is not a substance flowing the other way.
Insulation in real life
A wool jumper does not create heat. Its fibres trap air and slow the transfer of energy from your warm body to the cooler surroundings. The same idea is used in building insulation, oven gloves and cool boxes, although no ordinary insulation stops heat flow completely.
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