Chapter 4: States of Matter

 Chapter 4: States of Matter

The Three States

- Solid: Fixed shape and volume, particles tightly packed and vibrate in place.

- Liquid: Fixed volume but no fixed shape, particles slide past each other.

- Gas: No fixed shape or volume, particles move freely and rapidly.

Changes of State

- Melting: Solid → Liquid

- Boiling: Liquid → Gas

- Condensation: Gas → Liquid

- Freezing: Liquid → Solid

- Sublimation: Solid → Gas directly

These changes involve energy transfer and occur at specific temperatures for pure substances.

The Kinetic Theory

- Particles are in constant motion.

- Temperature increases → kinetic energy increases.

- Explains pressure, diffusion, and changes of state.

Ideal Gas Behaviour

- Gases consist of particles with negligible volume.

- No intermolecular forces.

- Collisions are elastic.

- Obeys the ideal gas equation:  

  pV = nRT

  - p: pressure (Pa)  

  - V: volume (m³)  

  - n: moles  

  - R: gas constant (8.31 J/mol·K)  

  - T: temperature (K)

Real Gases

- Deviate from ideal behaviour at high pressure and low temperature.

- Particles have volume and experience intermolecular forces.

- Van der Waals equation adjusts for these deviations.

Diffusion

- Movement of particles from high to low concentration.

- Gases diffuse faster than liquids.

- Rate depends on molar mass and temperature.