Key concepts
For moderate temperature changes, length change is approximately coefficient × initial length × temperature change. Heating usually expands materials; cooling contracts them.
Particle motion and dimensional changes are visually magnified. Coefficients are representative room-temperature values.
Applications and misconceptions
Applications: bridge joints, railway gaps, thermostats, power lines, thermometers, and precision instruments.
Explore: Why does a longer bridge require a larger expansion gap? Why is Invar useful in measuring tools?
Misconception: Individual atoms do not swell like balloons. Their average separation changes.