States of Matter

• What are the 3 states of matter?

  Solid

  Liquid

  Gas
• Solids

  Arrangement of particles: Regular

  Evidence of particles: Crystal shapes have straight edges - solids have definite shapes

  Spacing: Particles are close together

  Evidence of spacing: Solids are not easily compressed

  Movement: Vibrating about a point

  Evidence of movement: Diffusion is very slow - solids expand on heating
• Liquids

  Arrangement of particles: Random

  Evidence of arrangement: Liquids change shape to fill the bottom of the its container - can flow

  Spacing: Particles are close together

  Evidence of spacing: Liquids are not easily compressed

  Movement: Rapid jostling

  Evidence of movement: Diffusion is slow - liquids evaporate when heated
• Gases


  Arrangement of particles: Random

  Evidence of arrangement: Gas will fill into container

  Spacing: Particles are far apart

  Evidence of spacing: Gases are easily compressed

  Movement: Rapid

  Evidence of movement: Diffusion is rapid - gases exert pressure
• What are the state changes?

  Solid to liquid - melting

  Liquid to solid - freezing

  Liquid to gas - boiling

  Gas to liquid - condensation

  Solid to gas - sublimation

  Gas to solid - deposition

  
  

  These are all reversible reactions
• What is enthalpy?

  Change in heat energy measured under constant pressure

  Positive enthalpy change - endothermic reaction

  Negative enthalpy change - exothermic reaction
• What is temperature?

  Average kinetic energy of the particles
• What is the enthalpy change of fusion?

  Energy needed to change the state

  Solid to liquid

  Liquid to solid
• What is the enthalpy change of vaporisation?

  Energy needed to change the state

  Liquid to gas

  Gas to liquid
• What happens when you heat a solid?

  Energy supplied to the particles which makes them vibrate more about a fixed point

  Increases the average distance between the particles so the solid expands
• How does a solid turn into a liquid?

  Supply more energy to break the intermolecular forces between particles - this is the enthalpy change of fusion

  When a solid melts, the temperature does not change as the heat energy provided is absorbed to break the bonds
• What happens when you heat a liquid?

  Energy supplies to the particles which makes them move more quickly as they have more kinetic energy

  Increases the average distance between the particles so the liquid expands
• How does a liquid turn into a gas?

  Supply more energy to break all the intermolecular forces between particles - this is the enthalpy change of vaporisation

  When a liquid boils, the temperature does not change as the heat energy provided is absorbed to break the bonds
• What happens when you heat a gas?

  Particles gain kinetic energy and move faster

  Particles move apart so gases expand