P1.1 - Energy Transfer By Heating

P1.1 - Energy Transfer By Heating

1. INFRARED RADIATION

   • All objects EMIT and ABSORB infrared radiation. The hotter the object, the more infrared radiation it emits.
   • Dark/Matte surfaces are good absorbers of infrared radiation however they are bad REFLECTORS of radiation. Light and shiny surfaces are good reflectors of infrared radiation but BAD absorbers.

2. KINETIC THEORY

   • Kinetic theory is used to explain the different states of matter. The particles of solids, liquids and gases have different amounts of energy.
   • .In a GAS,the particles are usually far apart and move at random much faster. NO FIXED SHAPE AND CAN FLOW.
   • In a SOLID, the particles vibrate around fixed positions so the solid has a FIXED shape.
   • In a LIQUID, the particles are in contact with each other but can move about at random. They don’t have a fixed shape and can fit the shape of their container.

3. CONDUCTION

   • Conduction occurs mainly in solids. Most liquids and gases are poor conductors
   • Metals are EXCELLENT conductors. Metals have FREE ELECTRONS. Poor conductors are called insulators.

4. CONVECTION

   • Convection occurs in fluids (liquids and gases). When a fluid is heated, it expands. The fluid then becomes less dense and rises. The warm fluid is replaced by cooler/denser fluid.
   • Convection occurs when the more energetic particles move from the hotter region to the cooler region and take their heat energy with them

5. EVAPORATION AND CONDENSATION

   • The rate of condensation increases if the temperature of the gas is decreased. On the other hand, the rate of evaporation increases if the temperature of the liquid is increased.
   • It is also increased if the surface area of the liquid is increased ans air is moving over the surface of the liquid

6. ENERGY TRANSFER BY DESIGN

   • The greater the temperature difference between an object and its surroundings, the greater the rate at which that energy is transferred.
   • Sometimes we want to maximise the rate of energy transfer to keep things cool.

7. SPECIFIC HEAT CAPACITY

   • When we heat a substance, we transfer energy to it so the overall temperature is increased.

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