Changes of state

• What is a change of state?

  A physical change where a substance transitions between solid, liquid, and gas, without changing its chemical composition.
• What are the main changes of state?

  • Melting (solid -> liquid)
  • Freezing (liquid -> solid)
  • Boiling/Evaporation (liquid -> gas)
  • Condensation (gas -> liquid)
  • Sublimation (solid -> gas)
  • Deposition (gas -> solid)
• Is a change of state a physical or chemical change?

  Physical change, because no new substances are formed, and it can be reversed.
• What happens to particle energy during melting?

  Particles gain energy, move faster, and break some of their bonds, turning into a liquid.
• What happens to particle energy during freezing?

  Particles lose energy, move slower, and form stronger bonds, turning into a solid.
• What is the difference between boiling and evaporation?

  • Boiling occurs at a specific temperature (boiling point) throughout the liquid.
  • Evaporation happens at any temperature but only at the surface.
• What happens to particle energy during condensation?

  Particles lose energy, move closer together, and form a liquid.
• What is sublimation?

  When a solid changes directly to a gas without becoming a liquid, e.g., dry ice (solid CO2).
• What is specific latent heat?

  The energy required to change the state of 1 kg of a substance without changing its temperature.
• Why does temperature stay constant during a change of state?

  Energy is used to break or form bonds between particles rather than changing temperature.
• Why does sweating cool you down?

  Evaporation takes energy from your skin, transferring heat away and cooling you down.
• Why do gases have more energy than solids and liquids?

  Gas particles move faster, have weaker forces between them, and have more kinetic energy.