Conduction, Convection, Condensation, Evaporation and Radiation (P1)
- Created by: alexdakota
- Created on: 15-03-15 16:10
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- Heat Radiation
- heat energy transferred by:
- radiation
- conduction
- solids
- convection
- liquids and gases
- transfer of energy by particles
- the transfer of heat energy by infrared radiation
- emitted by solids, liquids and gases
- The bigger the temperature difference between a body and its surroundings, the faster energy is transferred by heating
- Hotter than surroundings- emits more radiation than it absorbs
- Cooler than surroundings- absorbs more radiation than it emits
- The hotter an object, the more radiation it radiates in a given time
- Dark, matt surfaces
- absorb and emit radiation well
- Solar hot water panels
- washing up
- radiators
- Light, shiny surfaces
- reflect most infrared radiation
- vacuum flask- silver inner surfaces to keep heat in or out (dependent)
- reflect most infrared radiation
- heat energy transferred by:
- Kinetic Theory and Concuction
- Solids
- strong forces of attraction
- particles close in a fixed, regular arrangement
- not much energy
- vibrate about fixed positions
- Liquids
- weaker forces of attraction
- particles can move and form irregular arrangements
- more energy
- move in random directions at low speeds
- Gases
- almost no forces of attraction
- most energy and free to move
- travel in random directions at high speeds
- Conduction of heat energy is where vibrating particles pass on their extra kinetic energy to neighbouringparticles
- causes a rise in temperature at the other side of the solid
- increase in heat radiating from its surface
- faster in denser solids because particles are closer together and so will collide more often
- increase in heat radiating from its surface
- Metals are good conductors
- electrons are free to move inside the metal
- At the hot end, electrons move faster and collide with other electrons, transferring heat
- causes a rise in temperature at the other side of the solid
- Insulators
- materials that have larger spaces between their particles
- conduct heat more more slowly
- Solids
- Convection
- occurs when the more energetic particles move from the hotter region to the cooler region- and take their heat energy with them
- Immersion heaters
- kettes
- radiators
- Condensation
- gas turns to a liquid
- gas cools, particles slow down and lose kinetic ernergy
- attractive forces pull particles together
- If the temperature gets cold enough and the gas particles get close enough, condensation can take place
- water vapour in the air condenses when it comes into contact with cold surfaces
- drinks glasses
- Gets faster if:
- temperature of gas is lower
- temperature of the surface the gas touches is lower
- density is higher
- airflow is less
- Evaporation
- liquid turns into gas
- when particles escape from a liquid
- Particles near the surface of a liquid can escape and become gas particles if:
- travelling in the right direction
- travelling fast enough to overcome attractive forces of other particles
- the fastest particles evaporate so the average speed and kinetic energy of the remaining particles decreases
- temperature of the remaining liquid falls
- cooling effect
- temperature of the remaining liquid falls
- Faster if:
- temperature is higher
- density is lower
- surface area is larger
- airflow over the liquid is greater
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