P1 Unit 1 Energy Transfer by Heating

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  • Created by: Phoebe
  • Created on: 10-04-12 15:26

Infra-red Radiation

ALL objects emit (give out) and absorb (take in) infra-red radiation.

The hotter an object is, the more infra-red radiation it emits.

Infra-red waves=part of the electromagnetic spectrum.

Unlike conduction and convection, radiation doesn't involve particles, only waves. This explains why we can still feel the heat of the Sun through the vacuum of space, even though there are no particles in a vacuum.

Surface and radiation

Some surfaces are better than others at emitting and absorbing infra-red radiation.

Dark and matt surfaces are good absorbers AND emitters of infra-red radiation    i.e. if you wear a black outfit on a hot day, you will become hotter than if you had worn a white outfit.

Light, shiny surfaces are poor absorbers and emitters of infra-red radiation, however they are excellent reflectors of infra-red radiation.

States of matter

3 states of matter: Solids, liquids and gases.

Solids: 

Particles are closely packed together, in a regular pattern. They cannot flow, but the particles vibrate about a fixed position. They have a fixed volume. They have a high density.

Liquids:

Particles are close together, but arranged randomly. They can flow, and move around each other. They always fit the shape of their container. They have a fixed volume, and a fairly high density, much higher than a gas.

Gases:

Particles are far apart and completely random. They can move quickly in any direction. They can fill a container, and their volume can be changed. They have a very low density.

A substance can change its state from one to another:

Red=cooling     Blue=heating

(http://i2.squidoocdn.com/resize/squidoo_images/-1/draft_lens18393858module152685903photo_13142543423_states_of_matter.gif)Conduction

Conduction occurs mainly in solids. Most liquids and ALL gases are poor conductors.

Metals are the best conductors. Copper is a better conductor than steel. Wood conducts better than glass.

Poor conductors are better known as insulators (fibreglass and wool are good insulators because they contain trapped air. Air is a rubbish conductor).

When one end of a solid is heated, the particles at one end gain kinetic energy and vibrate more. This energy gets passed on to the neighbouring particles, and thus the energy is transferred through the solid.

When metals are heated their free electrons gain kinetic energy and move through the metal, leaving their atoms behind and transferring energy by colliding with other particles.

Non-metals are poor conductors because they do not contain free electrons

Convection

Convection occurs in fluids (liquids and gases).

When a fluid is heated, it expands. The hot fluid becomes less dense and rises and causes circulation, as the warm fluid

Comments

:) PurpleJaguar (: - Team GR

Thanks for these notes they were very helpful :)

Victoria

this is an AMAZING resource!!! soo useful because it is everything tht we need to know! 

Thank You  :D **

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