Physics · 2.2.1 Thermal expansion
Thermal Expansion. Heat it.
Heating makes particles vibrate more and take up more space. See a bimetallic strip bend, and compare how much solids, liquids and gases expand for the same temperature rise. Gases expand most, solids least.
0625 Topic 2.2.1 — Thermal expansion
Bimetallic strip
Solids < liquids < gases
Variables
20
Live readouts
Temperature θ
20 °C
Strip deflection
0%
Particle picture
Heating gives particles more kinetic energy; they vibrate further apart, so the material expands. Mass is unchanged, so density falls.
Expansion order for the same temperature rise: gases ≫ liquids > solids.
📋 Key ideas (Cambridge)
- A bimetallic strip is two metals (e.g. brass and iron) bonded together. Brass expands more, so on heating the strip bends with brass on the outside. Used in thermostats and fire alarms.
- For the same temperature rise, gases expand most, then liquids, then solids — because particle spacing and bonding differ.
- Applications: expansion gaps in bridges and railway lines; expansion loops in pipes; the cause of a thermometer's liquid rising.
🎯 Syllabus reference (0625)
- 2.2.1 Thermal expansion of solids, liquids and gases — describe qualitatively the thermal expansion of solids, liquids and gases at constant pressure; explain in terms of the kinetic particle model; describe applications and consequences (bimetallic strip, gaps in structures).