- Before the discovery of the electron: atoms as tiny spheres that could not be divided.
- Plum Pudding Model: the atom as a ball of positive charge with negative electrons embedded in it.
- Rutherford's alpha scattering experiment: they shot alpha particles at gold foil. Most particles went straight through, some deflected, very few reflected. Conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged.
- Bohr: improved the nuclear model, saying that electrons orbit the nucleus at specific distances (shells). Experiments also found each proton as one unit of positve charge.
- Chadwick: showed the existence of neutrons in the nucleus 20 years after the nucleus was found.
- The atom has a positive nucleus surrounded by negatively charged electrons, with almost all of the mass in the nucleus.
- density = mass/volume
- density: kg/m3
- mass: kg
- volume: m3
- Mass is conserved when substances melt, freeze, evaporate, condense or sublimate
- Physical changes differ from chemical changes because the material recovers its original properties if the change is reversed
- Heating a system will change the energy stored within the system and raise its temperature - or produce a change in state.
- Specific heat capacity: the energy needed to raise the temperature of 1kg by 1o C.
- Specific latent heat: the energy needed to change state of 1kg of a substance.
- Fusion: solid to liquid.
- Vaporisation: liquid to vapour.
- E = mCAT (given in equation sheet)
- E - mL (given in equation sheet)
- If temperature increases, gas molecules gain more kinetic heat energy so move around faster.
- If pressure increases, gas molecules are closer together and will collide more with other molecules and the walls of the container.
- Increasing the temperature of a gas, at a fixed volume, increases the pressure exerted (because it will bump into walls of the container with more force).