# Energy Transfer

pretty much everything you need to know on this topic for GCSE, includes some equations

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• Energy Transfer
• Particles
• Solids
• set shape
• can't be compressed
• joined by bonds
• vibrations can pass through
• Liquids
• Can be poured
• takes the shape of the container
• can't be compressed
• Gas
• Not bonded
• can be compressed
• Why? - particles are so spread out so they can be compressed (squashed) together easily. While in solids and liquids the particles are more compact
• Evaporation- when a liquid turns into a gas
• Best  conditions for evaporation
• big surface area
• warm temperature
• dry
• windy
• not humid
• Our hands fell cold when using hand gel  because the gel takes the heat energy away from our hands
• A liquid cools down when it evaporates because
• 1. particles with the most energy evaporate
• 2. they have enough energy to overcome the forces from other particles
• 3. the average energy of the ones left behind decreases so the temperature decreases
• Condensation- when a gas turns into a liquid
• 1. gas cools so particles slow down ,lose kinetic energy and are pulled together
• 2. as the temp drops the particles get close enough together that condensation occurs
• Matt/ black surfaces
• good absorbers
• good emitters
• Shiny/silver surfaces
• good reflector
• poor emitter
• can travel through a vacuum
• travels in straight lines
• travels at the speed of light
• matt surfaces are the best at emitting infa-red radiation
• Convection
• 1. particles gain energy, move apart and become less dense so they rise
• 2. As the heated particles move away from the heat source, they cool,  become closer together and fall
• Conduction
• Solids are the best conductors because the particles are closer together
• 1. particles closest to heat source begin to vibrate more, which passes on the energy to surrounding particles
• 2. These surrounding particles also begin to vibrate faster until all particles are vibrating faster and the solid expands
• Metals are good conductors because they have free electrons, which move where they want and pass on energy quicker
• Payback time- cost divided by saving
• Cost effective- total saving minus the initial cost
• The lower the U value, the better insulator the material is
• Specific Heat Capacity
• E=M x C x 0
• E= energy transferred in joules (J)
• M= mass in kg
• C= specific heat capacity in J/kg degrees C
• 0= temperature change in degrees C
• Heat Transfer
• Cavity Wall
• stops convection, radiation and conduction
• Loft
• Draught proofing
• stops convection
• curtains
• Types of energy
• electrical
• whenever a current flows
• light
• sun, light bulbs
• sound
• noise
• kinetic
• movement
• thermal
• hot objects to cold
• gravitational potential
• anything that can fall
• elastic potential
• stretched springs, bands etc
• chemical
• foods and batteries