Particle model of matter

• density is how closely packed the particles are
• density equation


  density = mass / volume
• the changing of states is a physical reaction so it can be reversed by removing or adding heat energy. no mass is lost
• properties of a solid

  fixed shape and volume, highest density, particles vibrate on the spot, cant be compressed
• properties of a liquid

  fixed volume, fits the shape of the container, particles slide past each other, lower density than gas but higher than solid, cant be compressed
• Gas properties


  no fixed shape, fills the container, free to move, lowest density
• the internal energy is the combined kinetic and potential energy of the particles in a system
• evaporation can happen at any temperature on the surface whereas boiling can only happen at a certain temperature throughout the liquid e.g. 100 degrees for water.
• In a heating/cooling graph, the temperature increases/decreases until a change of state where it levels off as the energy is put into breaking the bonds
• Specific latent heat is the amount of energy needed to change the state of 1kg of a substance without changing its temperature
• specific latent heat equation

  energy = mass(kg) * specific latent heat
• particles in a gas are very far apart and and in constant random motion
• the pressure of the gas is caused by the particles colliding with the walls of the container
• a low temperature would lead to less pressure as the particles have less kinetic energy so less collisions
• a high temperature would lead to high pressure as the particles have more kinetic energy so more collisions
• Particles in a container exert a force on the walls of the container. always at right angles
• if we increase the volume while keeping the temperature constant, the pressure will decrease as they are inversely proportional

  Pv = constant
• If we compress gas in an enclosed container with a piston, we carry out work. we have transferred energy to the particles and increased its internal energy. As we have increased the kinetic energy, we have increased the temperature