Energy Transfer (P1)

Energy Transfer (P1)

1. Specific Heat Capacity

   • Specific heat capacity is the amount of energy required to change the temperature of 1kg of a material by 1°C.
     • E = m x c x θ
       • E is energy transferred (J), m is mass (kg), c is specific heat capacity (J/kg °C) and θ is temperature change (°C).

2. Kinetic Theory/States Of Matter

   • Gas: the particles move about quickly, randomly and are much farther apart than particles in a liquid or a solid.
     • Increase in temperature: the gas molecules move faster and the collisions become more intense.
     • Decrease in temperature: the gas molecules move more slowly, move closer together, the collisions become less frequent and the gas begins to form a liquid.
     • Less dense.
   • Explains the different states and properties of matter.
   • Liquid: the particles move in random and are in contact with each other.
     • They can flow.
     • They do not have a fixed shape.
     • They have fixed volume.
   • Solid: the particles have a fixed shape and volume.
     • They are dense.
     • They vibrate in a fixed position.

3. Energy Transfer By Design

   • The bigger the temperature difference between an object and its surroundings, the faster the rate which energy is transferred.
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     • The rate of which energy is transferred also depends on: the materials the object is in contact with, the objects shape, the objects surface area and volume, the type of material it's made from and its temperature.

4. Energy Transfer By Heating

   • Conduction
     • The transfer of heat through a material, without the material itself moving.
     • Metals are good conductors of energy.
       • When metals are heated their free electrons gain kinetic energy and move through the metal, transferring energy by colliding with other particles.
     • Non-metals, most liquids and all gases are (usually) poor conductors of heat.
       • These are known as insulators.
         • Wool and fibreglass is a good insulator because it traps air between the fibres and air is a poor conductor.
     • If one end of a solid is heated, the particles at that end gain kinetic energy and vibrate more. This energy is passed to neighbouring particles and in the way the energy is transferred through the solid.
   • Convection
     • Convection only takes place in liquids and gases (fluids).
       • Convection cannot occur in solids because the particles are held in fixed positions are not able to flow.
     • When a fluid is heated is becomes less dense and rises, resulting in a convection current.
       • Particles in the liquid or gas (nearest to the energy source) warm up causing the substance to expand and become less dense. The warm air then rises, as it does so it begins to cool down. The air becomes denser and eventually sinks. The cool, dense fluid replaces the air that has risen and the cycle repeats again.
     • Convection is the transfer of energy by heating through the movement of particles.
   • Evaporation
     • Evaporation is the transfer of energy at the surface of a liquid.
     • Evaporation is the process of a liquid changing into a gas.
       • Evaporation takes place because the most energetic liquid molecules escape from the liquid's surface and enter the air. Therefore the average kinetic energy of the remaining molecules is less, so the temperature of the liquid decreases.
         • The rate of evaporation is increased by: increasing the surface area of the liquid, increasing the temperature of the liquid and creating a draught of air across the liquid's surface.
   • Condensation
     • Condensation is the process of a gas changing into a liquid.
       • The rate of condensation is increase by: increasing the surface area and reducing the surface temperature.

5. U-Values

   • U-values give a measure of how effective a particular material is as an insulator.
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     • The lower the U-value, the better the material is as an insulator.

6. Keywords

   • Liquid.
   • Emit.
   • Solid.
   • Infrared Radiation.
   • Gas.
   • Conduction.
   • Evaporation.
   • Conductor.
   • Thermal Radiation.
   • Kinetic Theory.
   • Energy Transfer.
   • Insulator.
   • Convection.
   • Condensation.
   • Specific Heat Capacity.
   • U-Value.
   • Emitter.
   • Reflector.
   • Abosorber.
   • Free Electrons.
   • Convection Current.
   • Mass.
   • Fluid.
   • Temperature Difference.
   • Temperature.
   • Solar Heating Panel.

7. Infrared Radiation

   • Dark Matt Surfaces
     • Emit more radiation than light, shiny surfaces.
     • Absorb more radiation than light, shiny surfaces.
   • Light Shiny Surfaces
     • Poor emitters of thermal (infrared ) radiation.
     • Poor absorbers of infrared radiation.
     • Good reflectors of infrared.
   • All objects emit infrared radiation.
     • The hotter the object, the more radiation emitted within a given time.
     • The amount of infrared radiation an object takes in or gives out depends on it's surface, shape and dimensions.
   • Part of the electromagnetic spectrum, (between visible light and microwaves).
   • The energy transfer by electromagnetic waves.
   • Can travel through a vacuum.

8. Heating & Insulating Buildings

   • Solar heating panels contain water that is heated by radiation from the sun.
   • The rate of energy to or from our homes can be reduced.
   • Solar heating panels do not use fuel to heat water, but they are expensive to buy and install.