BRAINCAKEMatter
Revision notes for Matter in OCR Physics A (J249). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.
- How the atomic model has changedScientists change a model when new evidence does not fit it.
- The structure of the atomAn atom has a nucleus at its centre.
- The size of atoms and small moleculesAtoms and small molecules are tiny.
- DensityDensity is the mass of a substance in each unit of volume.
- Density and the states of matterThe density of a material depends on how closely its particles are packed.
- Density, mass and volume when mass is conservedThe equation density = mass ÷ volume can be rearranged.
- Conservation of mass in changes of stateWhen a substance melts, freezes, evaporates, condenses or sublimates, it changes state.
- Physical changes and chemical changesIn a physical change no new substance is made.
- Heating, internal energy and changes of stateThe particles in a substance have kinetic energy because they move, and potential energy because of the forces between them.
- 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 one degree Celsius (1 °C).
- Calculating energy changes using specific heat capacityThe energy needed to change the temperature of a material depends on three things: its mass, its specific heat capacity and the change in temperature.
- Calculating energy changes using specific latent heatThe energy needed to change the state of a substance, with no change in temperature, depends on its mass and its specific latent heat.
- Molecules, temperature and pressure of a gasThe molecules in a gas move randomly at high speed in all directions.
- Gas temperature and pressure at constant volumeTake a fixed mass of gas in a sealed container that cannot change size, so the volume is constant.
- Compressing gases and the force from pressureA gas can be compressed, which means squashed into a smaller volume, and it can expand into a larger one.
- Volume and pressure of a gas at constant temperatureSuppose a fixed mass of gas is kept at a constant temperature, and the volume it is held in is increased.
- Doing work on a gas to raise its temperatureWhen you push the plunger of a bicycle pump, a force moves through a distance and you do work on the air inside.
- A simple model of the atmosphere and atmospheric pressureThe Earth is surrounded by a thin layer of gas called the atmosphere.
- Atmospheric pressure and heightThe Earth is surrounded by a layer of air called the atmosphere, held in place by gravity.
- Floating and sinkingAny object placed in a fluid (a liquid or a gas) feels an upward force from the fluid called upthrust.
- Pressure in liquids and upthrustThe pressure in a liquid is caused by the weight of the liquid above a point.
- Calculating pressure differences in liquidsThe pressure due to a column of liquid can be calculated using: pressure (Pa) = height of column (m) × density of liquid (kg/m3) × gravitational…