P1 U1 Energy transfer by heating

Infared radiation
1. Infrared radiation is energy transfer by electromagnetic waves.
2. All objects emit infrared radiation
3. The hotter an object is the more infrared radiation it emits in a given time.
4. Infrared waves are part of the electromagnetic spectrum. They are the part of the spectrum just beyond visible red light. We can detect infrared radiation with our skin - it makes us feel warm.
5. All objects emit (give off) infrared radiation.
6. The hotter an object is the more infrared radiation it emits in a given time.
7. Infrared radiation can travel through a vacuum, as in travelling through space. This is how we get energy from the sun.
Surfaces and radiation
1. Dark, matt surfaces emit infrared radiation more quickly than light, shiny surfaces.
2. Dark, matt surfaces absorb infrared radiation more quickly than light, shiny surfaces.
3. Light, shiny surfaces reflect more infrared radiation than dark, matt surfaces.
4. 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.
5. Dark, matt surfaces are are also good emitters of infrared radiation. So an object that is painted dull black will transfer energy and cool down more quickly than the same object painted shiny white.
6. Light shiny surfaces are good reflectors of infrared radiation.
States of matter
1. The three states of matter are solid, liquid and gas. We can make a substance change between these states by heating or cooling it.
2. In a solid, the particles vibrate about fixed positions so the solid has a fixed shape.
3. 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.
4. 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.
5. Flow, shape, volume and density are the properties used to describe each state of matter.
6. The particles in a solid are held next to each other, vibrating in their fixed positions.
7. The particles in a liquid move about at random and are in contact with each other.
8. The particles in a gas move about randomly and are much further apart than particles in a solid or liquid.
Conduction
1. Metals are the best conductors.
2. Materials such as wool and fibreglass are good insulators.
3. Conduction in a metal is mainly due to free electrons transferring energy inside the metal.
4. Non-metals are poor conductors because they do not contain free electrons.
5. Conduction mainly occurs in solids. Most liquids and gases are poor conductors.
6. If one end of a solid is heated, the particles at that end gain kinetic energy and vibrate more. This energy is passedto neighbouring particles and in this way the energy is transferred through the solid.
7. This process occurs in metals.
8. In addition, when metals are heated their free electrons gain kinetic energy and move through the metal, transferring energy by colliding with other particles. Hence all metals are good conductors.
9. Poor conductors are called insulator. Materials such as wool and fibreglass are good insulators because they contain trapped air.
Convection
1. Convection occurs in fluids. Fluids are liquids and gases.
2. 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.
3. Convection currents can be on a very small scale, such as heating water in a beaker, or on a very large scale, such as heating the air above land and sea. Convection currents are responsible for onshore and offshore breezes.
4. Convection is the circulation of a fluid (liquid or gas) caused by heating it.
5. Convection takes place only in liquids and gases (fluids)
6. Heating a liquid or a gas makes it less dense so it rises and causes circulation.
Evaporation and condensation
1. Evaporation is when a liquid turns into a gas.
2. Condensation is when a gas turns into a liquid.
3. Evaporation is when a liquid turns into a gas. Evaporation takes place because the most energetic liquid molecules escape from the liquids 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.
4. The rate of evaporation is increased by:
  1. increasing the surface area of the liquid
  2. increases the temperature of the liquid
  3. creating a draught of air across the liquid's surface.
5. Condensation is when a gas turns into a liquid. This often takes place on cold surfaces such as windows and mirrors.
6. The rate of condensation is increased by:
  1. increasing the surface area
  2. reducing the surface temperature.

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P1 U1 Energy transfer by heating

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	Created by Abbie Edwards over 8 years ago