BRAINCAKEMatter
Revision notes for Matter in OCR Combined Science A (J250). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.
- Development of the atomic modelOur picture of the atom has changed as new evidence has appeared.
- The structure of the atomAn atom has a tiny nucleus at its centre.
- The size of atoms and small moleculesAtoms are incredibly small.
- Defining densityDensity tells us how much mass a material has in each unit of volume.
- Density and the states of matterThe particles in a substance have the same mass whatever state it is in.
- Density when mass is conservedThe equation density = mass ÷ volume can be rearranged.
- Conservation of mass in changes of stateMelting, freezing, evaporation, condensation and sublimation are all changes of state.
- Physical and chemical changesA physical change does not make a new substance.
- Heating and internal energyA system has energy stored inside it, called its internal energy.
- Specific heat capacity and specific latent heatThe specific heat capacity of a substance is the energy needed to raise the temperature of 1 kg of the substance by 1 °C.
- Calculating energy for a temperature changeThe change in thermal (internal) energy when a substance is heated or cooled is found from three things.
- Calculating energy for a change of stateThe energy needed for a change of state is found from the mass and the specific latent heat.
- Gas molecules, temperature and pressureThe molecules in a gas move quickly in random directions.
- Temperature and pressure of a gas at constant volumeImagine a fixed amount of gas sealed in a rigid container.