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| Frage | Antworten |
| What is 'infrared radiation'? | Electromagnetic waves between visible light and microwaves in the electromagnetic spectrum |
| The electromagnetic spectrum | |
| What is meant by the term 'emit'? | To give out radiation |
| Properties of infrared radiation | . We can detect infrared radiation with our skin - it makes us feel warm . It can travel through a vacuum. This is how we get energy from the sun |
| What is meant by the term 'absorber'? | A substance that takes in radiation |
| What is meant by the term 'emitter'? | A substance that gives out radiation |
| What is meant by the term 'reflector'? | A substance that reflects radiation |
| What surfaces are good absorbers? | Dark, matt surfaces are good absorbers of infrared radiation. An object painted dull black and left in the sun will become hotter than the same object painted shiny white. |
| What surfaces are good emitters? | Dark, matt surfaces are good emitters of infrared radiation. So an object painted dull black will transfer energy and cool down more quickly than the same object painted shiny white. |
| What surfaces are good reflectors? | Light, shiny surfaces are good reflectors of infrared radiation. |
| Properties of a solid | In a solid, the particles vibrate about fixed positions so the solid has a fixed shape |
| Properties of a liquid | In a liquid, the particles are in contact with each other but can move about at random, so a liquid doesn't have a fixed shape and can flow. |
| Properties of a gas | In a gas, the particles are usually far apart and move at random much faster, so a gas doesn't have a fixed shape and can flow. The density of a gas is much less than that of a solid or liquid. |
| What is conduction? | 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 this way the energy is transferred through the solid. |
| Why are metals such good conductors? | When metals are heated, their free electrons gain kinetic energy and move through the metal, transferring energy by colliding with other particles. |
| What is an insulator? | A material or object that is a poor conductor |
| Examples of insulators | Wool or fibreglass are good insulators because they contain trapped air. |
| What is convection? | When a fluid is heated, it expands. The fluid becomes less dense and rises. The warm fluid is replaced by cooler, denser fluid. The resulting convection current transfers energy throughout the fluid. |
| What is meant by 'convection current'? | The circular motion of matter caused by heating in fluids. |
| What energy transfer is responsible for onshore and offshore breezes? | Convection |
| Example of conduction | |
| Example of convection | |
| What is meant by 'evaporation'? | Turning from liquid into vapour |
| Why does evaporation take place? | 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. This means that evaporation causes cooling. |
| What increases the rate of evaporation? | .Increasing the surface area of the liquid .Increasing the temperature of the liquid .Creating a draught of air across the liquid's surface |
| What is condensation? | Condensation is when a gas turns into a liquid. This often takes place on cold surfaces such as windows and mirrors |
| The rate of condensation is increased by... | .Increasing the surface area .Reducing the surface temperature |
| The greater the temperature difference between an object and its surroundings... | ...The greater the rate at which energy is transferred. |
| The rate at which energy is transferred also depends on... | .The materials the object is in contact with .The object's shape .The object's surface area |
| To maximise the rate of energy transfer to keep things cool, we sometimes use things that... | .Are good conductors .Are painted dull black .Have the air flow around the maximised |
| Sometimes we want to minimise the rate of energy transfer to keep things warm. To do this we need to minimise the transfer of energy by conduction, convection and radiation. We may use things that.... | .Are good insulators .Are white and shiny .Prevent convection currents by trapping air in small pockets |
| What is meant by 'specific heat capacity'? | Energy needed by 1kg of the substance to raise its temperature by 1 degrees. |
| Specific heat capacity equation | E = m x c x E = energy transferred, J m = mass, kg c = specific heat capacity, J/kg degrees C = temperature change, degrees C |
| How do we work out a change in temperature? | Subtract the initial temperature from the final temperature |
| What is meant by 'energy transfer'? | Movement of energy from one place to another or one form to another |
| How can people minimise the rate of energy transfer out of their homes? | . Fibreglass loft insulation to reduce ET by conduction . Cavity wall insulation that traps air in small pockets to reduce ET by convection. . Double glazing to reduce ET by conduction . Aluminium foil behind radiators to reflect infrared radiation into the room. |
| What is a U-Value? | The U-Value of a material tells us how much energy per second passes through it. Knowing the U-Values of different materials allows us to compare them. The lower the U-Value the better the material is as an insulator. |
| What is a solar heating panel? | Sealed panel designed to use sunlight to heat water running through it. |
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