Describe condensation and solidification in terms of particles
2.2.3 Melting, Boiling and Evaporation
Condensation
When a gas loses energy, its particles slow down and start to stick together. Think of a crowd of dancers (gas particles) who are moving fast and far apart. When the music (energy) slows, they begin to hold hands and form a tighter group – that’s condensation. The particles are still moving, but they’re now closer together, forming a liquid. 🌬️➡️💧
- Occurs when a gas cools to its condensation point.
- Energy lost by the gas is released as heat to the surroundings.
- Example: Water droplets on a cold window.
Solidification
Solidification is the opposite of melting. Imagine the dancers now standing still in a neat line (solid). The particles have lost almost all kinetic energy and are locked in a fixed arrangement. They vibrate but don’t move freely. ❄️
- Occurs when a liquid cools to its freezing point.
- Particles lose energy, reducing their vibration amplitude.
- Resulting structure is a rigid lattice.
Key Phase‑Change Relationships
| Phase | Particle Motion | Heat Transfer |
|---|---|---|
| Gas → Liquid (Condensation) | Fast, far‑apart → Slower, closer together | Heat released (latent heat of condensation) |
| Liquid → Solid (Solidification) | Vibrating in place → Fixed lattice | Heat released (latent heat of fusion) |
- Condensation: gas → liquid, heat released.
- Solidification: liquid → solid, heat released.
Practical Example: Ice Cream Maker
In an ice cream maker, the mixture (liquid) is cooled in a freezer. As it reaches the freezing point, it begins to solidify. The machine agitates the mixture, preventing large ice crystals from forming. The result is a smooth, solid ice cream. The process involves both solidification and the release of latent heat. 🍦
Revision
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