Heating & 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
• Temperature


  A measure of how hot or cold a substance is, measured in degrees Celsius, °C
• Heat


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

  Energy stored in heated objects
• 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
• Temperature


  A measure of how hot or cold a substance is, measured in degrees Celsius, °C

  
• Heat


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

  
• Thermal energy


  Energy stored in heated objects
• The direction of movement of energy between two objects of different temperatures


  Hot to cold

  
• Energy transfers from the hotter to the cooler object
• The transfer of energy between two objects or areas at different temperatures continues until both objects are at the same temperature
• Law of conservation of energy


  Energy cannot be created or destroyed, only transferred or stored
• What causes an object to have energy in its thermal energy store

  The vibration or movement of its particles

  
• What happens when particles gain more energy

  The particle vibrates more
• What factor affects the amount of energy contained in the object's thermal energy store

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

  Its mass
• Conduction


  The way solids transfer energy

  
• Convection


  The way fluids (liquids and gases) transfer heat

  
• What method of heat transfer causes heat to be transferred to the air above a cup of hot tea

  Convection
• Solid


  A material with particles that vibrate around fixed positions
• Thermal conductor


  A substance that transfers energy by conduction quickly
• Thermal insulator


  A substance that transfers energy by conduction slowly or not at all

  
• Thermal insulator


  A material that is a poor thermal conductor
• Conduction occurs in substances with touching particles
• 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
• Conduction is very slow in liquids because the particles are loosely packed, so they don't collide often
• Conduction rarely happens in gases because the particles are spread out, so the particles rarely collide
• Conduction doesn't occur in a vacuum because there are no particles
• Energy is transferred through a solid by conduction

  
• Energy transfer by conduction can be reduced by placing a layer of insulating material inside the solid (e.g. air)
• Density


  A measure of how heavy a certain volume of a material is
• Density (⍴)


  Measured in kilograms per cubic metre (kg/m³)