Three States of Matter

Overview

Introduction to the three states of matter: solid, liquid, gas.
Explanation of particle theory as a model to understand how substances change states.

Particle model: Each particle is considered as a small, solid, inelastic sphere.

Strong forces of attraction between particles.
Particles are held close together in a:
- Fixed position
- Regular lattice structure
Characteristics:
- Keeps a definite shape and volume.
- Cannot flow like liquids.
- Particles can vibrate but remain in fixed positions.
Heating a solid:
- Particles gain energy, vibrate more.
- At melting point, particles can break free and the solid melts into a liquid.

Weaker forces of attraction compared to solids.
Particles are:
- Free to move around.
- Arranged randomly.
Characteristics:
- Definite volume but not definite shape (can flow to fit a container).
Heating a liquid:
- Particles gain energy, move faster.
- At boiling point, particles break bonds and the liquid evaporates into a gas.

Very weak forces of attraction between particles.
Particles can:
- Move freely.
- Not keep a definite shape or volume (fill the container).
Movement:
- Gases exhibit random motion (travel in straight lines but can be deflected).
Heating a gas:
- Particles gain energy and travel faster.
- Gas expands if in an expandable container (like a balloon) or increases pressure in a fixed container.
Cooling a gas:
- Particles lose energy, bonds form, condensing the gas into a liquid.
Further cooling a liquid:
- Particles lose energy further, bonds form, freezing the liquid into a solid.

The particle model is an idealization:
- Particles aren't actually solid, inelastic spheres; they are atoms, ions, or molecules.
- The model does not detail the forces between particles (strength, quantity, etc.).
Despite limitations, the model is a useful simplification for understanding complex concepts.