AQA GCSE Science P1 notes

Kinetic TheoryKinetic theory is the arrangement and movement of particles in solids, liquids and gases.A solid's particles have the least energy, the particles in liquids have some energy and a gas's particles have the most energy.In solids, particles are packed tightly together and vibrate around fixed positions, this means solids have fixed shapes and volumes.In liquids, particles are arranged close together (Not in neat rows or columns) but are moving in no fixed way. Liquids have a fixed volume and take the shape of its container.In gases, particles are very far apart and move randomly and quickly. Gases fill a space available and have no fixed volume.When a solid is heated, it expands because the particles gain energy and move more.When a liquid is heated, it expands as well - used in thermometers.When a gas is heating, it also expands and takes up more space.

Infrared RadiationAll objects emit infrared radiation, the warmer they are, the more they emit. All objects can absorb infrared radiation.Infrared radiation doesn't require the presence of particles, as it is an electromagnetic wave (Which also means it travels at the speed of light).Infrared radiation can be detected with a special camera (Thermogram), but our eyes can't see it.Thermograms can be used to create heat maps, these heat maps can analyse a house's insulation or detect injury.Dark objects absorb heat best (Dull/matte surfaces are better at absorbing heat than shiny surfaces), and light object reflect heat more (Shiny surfaces reflect more heat than dull surfaces).Dark objects lose heat rapidly and light objects lose heat slower.

ConductionMetals with free electrons conduct heat better because the electrons are delocalised and free to move. Metals are also better at conducting because the atoms are arranged in neat rows.Atoms near the source of heat gain energy and vibrate more, it then bumps into its neighbour and the heat energy will be passed along the atoms.An object which is poor at conducting is called an insulator. Usually, they conduct heat worse because their atoms aren't arranged neatly and have no free electrons. Air is a good insulator because its particles are very far apart.

ConvectionConvection can only happen in gases and liquids because it relies on particles moving around freely.Particles near a heat source will gain energy and move around more, taking up more space, and then rise because its surroundings are more dense. The liquid/gas then cools because it looses energy and transfers its energy to surrounding cool particles, it then becomes more dense and sinks to the bottom again. The cycle then repeats. Never say that heat rises. It's the expanded liquids/gases that expand and rise.

Generating Energy A turbine is something that moves and is connected to a generator which then generates electricity.Steam is used to turn turbines. A lot of coal, oil, gas and biofuel are used to heat water to turn into steam so the steam turns the turbine. Nuclear fuel (Plutonium and uranium) generate heat through nuclear fission (Which is when the nucleus of an atom are split into smaller nuclei, this releases a large amount of energy). This heat is then used to evaporate steam to move a turbine. Nuclear stations produce a lot of energy and emit no polluting gases but they also produce radioactive waste and a high decommissioning cost.