Bridges are built with gaps, power lines sag in summer, and a tight metal lid loosens under hot water. All of it comes from one quiet fact: warm something up and its particles jostle harder, nudging each other a little farther apart.
Most substances expand when heated, because the particles vibrate or move more and take up slightly more space on average. For the same temperature rise, solids expand least and gases expand most.
Thermal expansion is the increase in size of a substance when its temperature rises, because its particles move more vigorously and their average separation increases.
The particles do not grow; only the spaces between them increase.
Raise the temperature of a solid and watch how its length grows as the particles vibrate more.
Four quick checks. Each correct answer earns XP and lights this skill on your star map.
When a metal bar is heated it usually...
A substance expands on heating because its particles...
For the same temperature rise, which expands most?
Gaps are left between railway rails to allow for...
The same effect appears in all three states, but to very different degrees, with important everyday uses.
Heating does not make the individual atoms or molecules larger. They stay the same size; the substance expands because the particles move more energetically and the average gap between them grows.
Unlocks once the four checks above are done. Worth more XP, written in the style of Paper 2.
A bimetallic strip bends when heated because the two metals...
The order of expansion for the same temperature rise, from least to most, is...
Overhead power lines are hung loosely between poles so that they can...
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