Physics - P1 - AQA - GCSE - Heating and Cooling

Infrared Radiation is emitted and absorbed by all objects. Warmer objects give out more, while cooler objects give out less.
1. IR is a type of electromagnetic wave. As it is a wave, it can pass through a vacuum.
  1. Dark, matt surfaces are better at absorbing and emitting IR.
  2. Light, shiny surfaces are poorer at absorbing and emitting IR. However, they are better reflectors.
The Kinetic Particle theory explains the properties of the different states of matter.
1. Particles are solids, liquids and gases.
  1. Solids
    1. Close together, regular pattern.
    2. Vibrate in a fixed position.
    3. Fixed shape, cannot flow as the particles are not free to move
    4. Cannot be squashed or compressed
  2. Liquids
    1. Fairly close together, mixed up randomly
    2. Move around each other
    3. Can flow, take up any container as the particles can move.
    4. Cannot be compressed as the particles are too close together already
  3. Gases
    1. Far apart, random
    2. Move in any direction
    3. Can flow and fill up any container, free particles
    4. Can be compressed as the particles are far away
Conduction
1. Heat transfer by conduction happens when heat it applied to a solid, such as a metal.
  1. The heat give the metal atoms energy, so they begin to vibrate and transfer the energy around them.
    1. This means that the heat energy is moved around the object- it has been conducted through the atoms.
Convection
1. Because gases and liquids are fluids, they expand when they are heated- because the particles move more with the extra energy.
  1. As a result, the particles take up more volume, because the gap between them becomes bigger.
    1. Warmer particles are less dense than colder particles, so will rise. This moves the colder particles down into the warmer area, warming it up, which then rises and replaces the now colder particles at the top.
Evaporation
1. When a liquid has enough energy, it will become less dense. At a point, the liquid will become a gas. Some remaining particles have a lower average kinetic energy than before, so the liquid cools down as evaporation happens.
  1. This is why sweating cools you down. The sweat absorbs energy from your skin, evaporating it.
  2. Increased surface area- more reactions.
    1. Moving air over liquid surface
Condensation
1. Some particles in a gas have different energy to others. Some may not have enough energy to remain as seperate particles, especially if the gas is cooled down.
  1. They form bonds as they come closer together, releasing energy, which is why water vapour can burn- energy is released as your skin condenses the gas.
    1. This means that the gas becomes a liquid.
2. Factors affecting condensation and evaporation
  1. Decreased temperature

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Physics - P1 - AQA - GCSE - Heating and Cooling

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