Changing state

• What happens to particles in a solid when it is heated?


  The particles gain more energy.
• How does heating a solid affect the forces holding it together?


  Heating weakens the forces that hold the solid together.
• What is the temperature called at which a solid turns into a liquid?

  Melting point.
• What is the process called when a solid turns into a liquid?

  This process is called melting.
• What happens to particles in a liquid when it is heated?


  The particles gain even more energy.
• What effect does heating have on the bonds holding a liquid together?


  Heating weakens and breaks the bonds holding the liquid together.
• What is the temperature called at which a liquid turns into a gas?


  Boiling point.
• What is the process called when a liquid becomes a gas?

  This process is called boiling or evaporating.
• What are the states of matter and their transitions?


  • Solid to Liquid: Melting
  • Liquid to Gas: Boiling (Evaporating)
  • Liquid to Solid: Freezing
  • Gas to Liquid: Condensing
• What happens to particles at the melting point?


  Many bonds have formed between the particles holding them in place.
• What occurs when a liquid cools down?

  The particles have less energy and move around less.
• What happens at the boiling point regarding gas particles?


  So many bonds have formed that the gas becomes a liquid.
• What is the relationship between the strength of forces between particles and the energy needed to change state?


  The stronger the forces, the more energy is needed to break them.
• How can you predict the state of a substance at a certain temperature?


  If below the melting point, it’s a solid; if above the boiling point, it’s a gas; if in between, it’s a liquid.
• At what state is a substance if the temperature is 25 °C and its melting point is -7 °C and boiling point is 59 °C?


  The substance is a liquid.
• What state is ethanol in at 25 °C if its melting point is -114 °C and boiling point is 78 °C?


  Ethanol is a liquid at 25 °C.
• What is the melting point of ethanol?


  • 114 °C.
• What is the boiling point of ethanol?


  78 °C.
• What happens to particles and forces during heating and cooling of substances?


  • Heating:
  • Particles gain energy and move faster.
  • Forces between particles weaken.
  • Cooling:
  • Particles lose energy and move less.
  • Forces between particles strengthen.