Thermal Expansion and Contraction Notes

Part A: Recap - Properties of the 3 States and Particle Model

  • Solids

    • Particle Arrangement: Packed closely together in a regular pattern.
    • Particle Movement: Vibrate in a fixed position.
    • Fixed Shape: Yes, due to the regular particle arrangement.
    • Fixed Volume: Yes, particles are close together with little space.

  • Liquids

    • Particle Arrangement: Packed closely together but in an irregular pattern.
    • Particle Movement: Move and slide over one another.
    • Fixed Shape: Not fixed, particles in irregular pattern can slide over each other.
    • Fixed Volume: Yes, particles are close together with little space.

  • Gases

    • Particle Arrangement: Far apart from each other and in irregular pattern.
    • Particle Movement: Move freely in any direction.
    • Fixed Shape: No, particles in irregular pattern.
    • Fixed Volume: No, particles are far apart from each other, with a lot of space between them.

Part B: Thermal Expansion and Contraction

  • Heating a Substance

    • Particles: Gain energy.
    • Particle Vibration: Vibrate more strongly.
    • Distance between Particles: Further apart.
    • Spaces between Particles: Larger.
    • Substance: Expands.

  • Cooling a Substance

    • Particles: Lose energy.
    • Particle Vibration: Vibrate less strongly.
    • Distance between Particles: Closer together.
    • Spaces between Particles: Smaller.
    • Substance: Contracts.

Change of States

  • Heating leads to absorption of energy.
  • Cooling leads to releases of energy.

Concept Check: True or False?

  1. When we cool a substance, the particles stop moving. (False)

    • Particles move less strongly, but they do not stop moving entirely.

  2. When we heat a substance, the particles expand. (False)

    • Substances expand, not the individual particles themselves.

  3. When we heat a substance, the mass increases. (False)

    • Mass remains unchanged during heating.

  4. When we heat a substance, the volume increases. (True)

  5. When water changes to ice, energy is absorbed. (False)

    • Energy is released when water changes to ice.