CHEM Kinetic Particle Theory

Kinetic Particle Theory

2.1 How Are Solids, Liquids, and Gases Different?

• Kinetic Particle Theory:
  • Matter consists of tiny particles (atoms, molecules, or ions). These particles are in constant random motion.
  • The arrangement and movement of these particles determine the physical state of matter (solid, liquid, or gas).
• States of Matter:
  • Solid:
    • Fixed volume and shape.
    • Particles are closely packed in an orderly manner and vibrate/rotate about fixed positions.
    • Very strong forces of attraction.
    • Very low kinetic energy.
  • Liquid:
    • Fixed volume, takes the shape of its container.
    • Particles are closely packed in a disorderly manner and slide past each other.
    • Less strong forces of attraction.
    • Low kinetic energy.
  • Gas:
    • Takes on the volume and shape of its container.
    • Particles are far apart in a disorderly manner and move quickly and randomly.
    • Very weak forces of attraction.
    • High kinetic energy.

Changes in State

• Changes in state occur at transition temperatures (e.g., melting, freezing, boiling points).
• Heating a substance increases the kinetic energy of its particles, potentially leading to a change in state.
• Cooling a substance decreases the kinetic energy of its particles, potentially leading to a change in state.

2.2 What Happens During Solid-Liquid Transitions?

• Melting:
  • Solid changes to liquid due to increased kinetic energy overcoming forces of attraction.
  • Temperature remains constant at the melting point until all solid has melted.
• Freezing:
  • Liquid changes to solid as particles lose energy, and forces of attraction draw them closer.
  • Temperature remains constant at the freezing point until all liquid has solidified.
• Expansion and Contraction:
  • Heating causes expansion as particles vibrate more quickly with slightly wider spacing.
  • Cooling causes contraction as particles vibrate slower and come closer together.

2.3 What Happens During Liquid-Gas Transitions?

• Evaporation:
  • Particles at the surface of a liquid gain enough energy to escape as a vapor.
• Boiling:
  • Liquid changes to gas throughout the liquid at the boiling point.
  • Temperature remains constant until all liquid has turned to gas.
• Condensation:
  • Gas cools, loses kinetic energy, and forms a liquid as particles come closer together.

2.4 What Happens During Solid-Gas Transitions?

• Sublimation:
  • Solid changes directly into a gas.
  • Particles gain enough thermal energy to overcome strong forces of attraction.
• Vapor Deposition:
  • Gas changes directly into a solid.
  • Particles in a gas are cooled, slow down, and arrange into a solid state.

Interconversion of Matter

The interconversion between the states of matter are:

• Melting:
  • $Solid \rightarrow Liquid$
• Evaporation/Boiling:
  • $Liquid \rightarrow Gas$
• Sublimation:
  • $Solid \rightarrow Gas$
• Freezing:
  • $Liquid \rightarrow Solid$
• Condensation:
  • $Gas \rightarrow Liquid$
• Vapor Deposition:
  • $Gas \rightarrow Solid$