Matter Changes Its State

Key notes :

Definition of Matter States:

  • Matter exists in three primary states: solid, liquid, and gas.
  • The state depends on the arrangement, movement, and energy of particles.

Interconversion of States:

  • Matter can change states (e.g., solid to liquid, liquid to gas) due to changes in temperature or pressure.
  • These changes are physical changes, as they don’t alter the chemical composition.

Processes of State Changes:

  • Melting: Solid → Liquid (e.g., ice melting into water).
  • Freezing: Liquid → Solid (e.g., water freezing into ice).
  • Evaporation: Liquid → Gas (e.g., water turning into vapor at its surface).
  • Boiling: Liquid → Gas (e.g., water boiling at 100°C).
  • Condensation: Gas → Liquid (e.g., water vapor condensing into droplets).
  • Sublimation: Solid → Gas directly (e.g., dry ice sublimating into carbon dioxide gas).

Role of Temperature:

  • Adding heat increases the kinetic energy of particles, causing them to overcome intermolecular forces and change state.
  • Removing heat decreases kinetic energy, allowing particles to come closer and change state.

Latent Heat:

  • Latent Heat of Fusion: The heat required to change 1 kg of a solid into a liquid at its melting point.
  • Latent Heat of Vaporization: The heat required to change 1 kg of liquid into gas at its boiling point.

Effect of Pressure:

  • Increasing pressure can compress particles and force matter into a denser state (e.g., gas to liquid).
  • Decreasing pressure allows particles to expand and move apart (e.g., liquid to gas).

Examples in Daily Life:

  • Boiling water for cooking.
  • Ice cubes melting in a drink.
  • Fog formation from condensation.
  • Sublimation of mothballs or dry ice.

Energy and State Changes:

  • State changes are energy-dependent:
    • Endothermic Processes: Absorb energy (e.g., melting, evaporation).
    • Exothermic Processes: Release energy (e.g., freezing, condensation).

Heating Curve of Water:

  • A graph showing temperature changes as heat is added:
    • Flat portions represent phase changes (e.g., melting and boiling).
    • Sloped portions indicate temperature increase in a single state.

Applications:

  • Refrigeration systems use condensation and evaporation cycles.
  • Industrial processes like distillation involve state changes.

Let’s practice!