Thermal insulation — Engineering, 11–13 years
Insulation slows the movement of heat. Engineers use trapped air, foam, fibres or reflective surfaces to keep heat in, keep heat out, or protect people from hot and cold parts.
Heat moves
Heat naturally spreads from a warmer place to a cooler one. Insulation does not make a perfect wall against heat; it makes that spreading slower. A winter coat, a thermos and the foam in a cool box all use spaces or materials that make heat take longer to cross.
The problem of heat loss
Buildings and containers often need a steady temperature, but heat leaks through walls, roofs and lids. Without insulation, a heated room loses energy and a cold drink warms quickly. Engineers add insulation when keeping a temperature saves energy, protects a product or makes a place comfortable.
Testing two cups
Pour 200 millilitres of hot water into two identical cups. Wrap one in 3 centimetres of foam and leave the other bare. After 30 minutes, the bare cup is 48°C and the wrapped cup is 58°C. The wrapped cup lost less heat: compare the 10-degree difference, while keeping water amount, starting temperature and time the same.
The sensible mistake
A common thought is that insulation makes something hot or cold. It does not add coldness to ice or heat to soup; it slows the exchange with the surroundings. The same material can help in both directions: it keeps a warm object warm and a cool object cool for longer.
Where it appears
House walls, lofts and windows use insulation to reduce heating and cooling needs. Fridges use insulation to slow heat entering, while insulated pipes stop hot water losing heat on its journey. Ovens also insulate their outer walls so the inside can be hot without making the outside equally hot.
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