Heating and Cooling

• Condensing

  The change of state when a gas turns into a liquid
• Freezing

  The change of state when a liquid turns into a solid
• Boiling

  The change of state when a liquid turns into a gas
• Melting

  The change of state when a solid turns into a liquid
• Heat


  A measure of the amount of energy contained in an object's thermal energy store, measured in joules, J

  
• The direction of movement of energy between two objects of different temperatures


  Hot to cold
• Energy transfers from the hotter to the cooler object
• What causes an object to have energy in its thermal energy store

  The vibration or movement of its particles

  
• What factor affects the amount of energy contained in the object's thermal energy store

  Its temperature
• Convection


  The way fluids (liquids and gases) transfer heat
• What happens to the particles in a substance as it's being heated

  They gain energy and vibrate more

  
• Stages of energy transfer by conduction

  1. Particles that are heated gain energy

  2. The increase in energy causes the particles to vibrate more

  3. The particles that are vibrating more collide into the particles around them, transferring the energy

  4. The movement of energy through a solid is called conduction

  
• How conduction occurs through a metal rod that is being heated by a Bunsen burner

  1. The Bunsen burner flame heats the metal rod

  2. As they are heated, the particles in the rod gain energy and vibrate more

  3. The heated particles collide with nearby particles, causing them to also vibrate more

  4. As more and more particles vibrate, there are more and more collisions, so energy transfer continues throughout the metal rod

  5. Eventually the temperature of the whole rod increases
• Density


  A measure of how heavy a certain volume of a material is
• Volume (V)


  Measured in cubic metres (m³)
• Use a digital scale to measure the mass of a material
• How to calculate the volume of a regular shaped solid e.g. a cube

  1. Measure the length, height and width using a ruler

  2. Use the formula: volume = length x height x width
• Fluids


  Liquids and gases, where the particles are free to move
• What hot air does compared to cold air

  Rise above

  
• How differences in density cause convection current in a room

  1. The radiator gives out heat

  2. The air around the radiator heats up

  3. The hot air is less dense, so it rises

  4. Then the denser cold air sinks

  5. The cold air is then heated by the radiator

  6. This movement of hot and cold air is called a convection current