States of matter
Heat and cool a substance and watch the particles change arrangement, separation and motion in real time.
- Particle arrangement
- Changes of state
- Temperature and kinetic energy
State
liquid
Temperature
300K
Wall collisions
1039/s
Relative pressure
99kPa
Predict
A sealed gas is heated at constant volume. What happens to the pressure?
Experiment
- 1Start at 150 K and raise the temperature slowly through 273 K and 373 K. Note where the arrangement changes.
- 2Set the temperature to 500 K, then shrink the volume. Watch the collision rate.
- 3Compare the collision rate at 300 K and 600 K with the volume unchanged.
Explain
Heating gives particles more kinetic energy. At a change of state the energy goes into overcoming the forces of attraction between particles instead of raising the temperature — which is why heating curves have flat sections.
Gas pressure comes from collisions with the container walls. Raise the temperature and the collisions become more frequent and harder. Shrink the volume and the same particles hit a smaller area more often. Both raise the pressure.
For a fixed mass of gas at constant temperature, p₁V₁ = p₂V₂.