p3 particle model of matter

• density = mass per unit volume
• density = mass / volume
• gases have the most kinetic energy, particles can move freely and have the lowest density
• in liquids particles are quite close together and move randomly. move rapidly in all directions and collide more frequently than in gases - can flow over each other
• particles in a solid can only vibrate around fixed positions/points, they have the highest density and the least kinetic energy
• changes of state are physical changes
• mass is always conserved in changes of state
• chemical changes cannot easily recover their original properties
• physical changes - if change is reversed the material's properties can be recovered
• temperature increases depending on material type, material mass and the energy inputted
• specific heat capacity is measured in J/kg degrees
• latent heat of vaporisation = changing from liquid to vapour
• energy = mass x specific heat capacity x change in temperature
• energy = mass x specific latent heat
• pressure in gases - pressure produces a force at right angles to the container it is in
• The specific latent heat of fusion refers to when a substance changes from a solid to a liquid (or vice versa).
• The specific latent heat of vaporisation refers to when a substance changes from a liquid to a gas (or vice versa).
• Increasing concentration increases pressure (in a fixed volume container)
• Increasing temperature increases pressure (in a fixed volume container)
• Increasing temperature increases volume (in a flexible container)
• If the gas is trapped within a container that cannot expand, it means that the volume of the gas is fixed, and so the pressure inside the container increases. 
• how volume affects pressure in a gas:

  1. Decreasing the volume of the container, whilst keeping the number of gas particles the same, will increase the concentration.
  2. In this smaller volume, collisions between particles of gas and the walls of the container will be more frequent.
  3. A greater number of collisions per unit area of wall means the pressure increases.
• faster moving particles and more collisions with the wall of the container can increase the pressure of gas
• gas does not have a definite shape or volume
• liquid has a definite volume but can be any shape
• solids have a definite volume and shape
• how temperature and concentration affect a flexible container:

  1. Some containers, such as balloons, are flexible.
  2. An increase in force on the walls of the container would just cause the container to expand.
  3. Therefore, changing temperature or concentration will change the volume of the container, rather than the pressure of the gases inside.
• To convert from per cm3 to per m3 you need to multiply by 1,000,000
• whilst a substance changes state, the temperature remains constant