P3

• Matter


  Sub-atomic particles and anything made from them, such as atoms and molecules
• Solids


  • Particles are tightly packed in a regular structure
• Liquids


  • Particles are tightly packed but free to move past each other
• Gases


  • Particles are spread out and move randomly
• Matter


  Made up of small particles called atoms
• Atoms


  Can exist on their own or together as molecules
• Density


  A measure of compactness and the ratio of mass to volume, usually measured in kg/m³ or g/cm³
• Mass


  The amount of matter an object contains, measured in kg or g
• Density


  A measure of compactness and the ratio of mass to volume, usually measured in kg/m3 or g/cm3
• Volume


  The amount of space or capacity a three-dimensional shape occupies
• Displacement can


  Used to measure volume of irregular solids by measuring the volume of water displaced
• Displaced


  Moved out of position, e.g. an object placed in water displaces the water causing the level to rise
• States of matter


  Solid, liquid or gas
• Evaporation


  A change of state from liquid to gas
• Solid


  • Particles in a regular arrangement
  • Particles vibrate about a fixed position
  • Particles sit very closely together
• Liquid


  • Particles are randomly arranged
  • Particles move around each other
  • Particles sit close together
• Gas


  • Particles are randomly arranged
  • Particles move quickly in all directions
  • Particles are far apart
• Sublimation


  A solid turns straight into a gas on heating, without becoming a liquid first - or when a gas turns straight into a solid, without becoming a liquid
• Boiling


  An active process where energy is applied to a liquid to turn it into a gas
• Evaporation


  A passive process where the liquid slowly absorbs energy from the surrounding area so that some of its particles gain enough energy to escape the liquid
• Throughout all of these changes the number of particles does not change, just their spacing and arrangement. As a result the total mass does not change.
• These changes in state are called physical changes because the process can be reversed (eg by cooling instead of heating). This is different to the changes seen in a chemical reaction, which cannot be reversed so easily.
• Internal energy


  The total amount of kinetic energy and chemical potential energy of all the particles in the system
• Energy required by different materials

  Depends on their 'heat capacity' and 'latent heat'
• When a material is heated or cooled, two changes may happen to the particles within the material:
• Internal energy


  The total kinetic energy and potential energy of the particles in an object
• Chemical bonds between the particles

  • May form, break or stretch
  • There is a change in the chemical potential store of energy in the material
• Temperature


  A measure of the average kinetic energy of particles in a substance
• Particles within the material

  • May gain or lose speed
  • There is a change in the thermal store of energy within the material
• Heating water


  Causes the water molecules to gain kinetic energy and speed up
• When energy is given to raise the temperature

  Particles speed up and gain kinetic energy
• It takes more energy to raise the temperature of a large amount of water because more molecules need to have their speed changed
• When the substance melts or boils

  Energy is put in to breaking the bonds that are holding particles together, which increases the potential energy
• The conservation of energy means that, assuming no energy is lost to the environment, any energy transferred to a material will be distributed between the chemical store and the thermal store of the internal energy
• Internal energy


  The total kinetic energy and potential energy of the particles in an object
• Specific heat capacity


  The amount of energy needed to raise the temperature of 1 kg of substance by 1°C
• Specific latent heat


  The amount of energy needed to melt or vaporise 1 kg at its melting or boiling point
• Specific latent heat is the amount of energy required to change the state of 1 kilogram (kg) of a material without changing its temperature
• Types of specific latent heat

  • Latent heat of fusion - the amount of energy needed to melt or freeze the material at its melting point
  • Latent heat of vaporisation - the amount of energy needed to boil or condense the material at its boiling point
• Thermal energy


  A more formal term for heat energy