# Physics GCSE (1)

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Notes.

Specific Latent Heat is the amount of energy needed to change the state of 1kg of a substance. It is calculated by E=Mass x SLH. The SLH of water is 2257kJ/kg. So if i had 2kg of water i would need 4514kJ to change its state.

Specific Heat Capacity is the amount of energy needed to raise or lower the temperature of 1kg of a substance by 1C. It is calculated by E=Mass x SHC x Temperature Change. The amount of energy needed is affected by the amount of intermolecular bond within the substance. The Specific Heat Capacity of water is 4.2J. If i had 10kg and i wanted to change the temperature from 21C to 25C I would need 168J.

Insulation is how we keep heat within out houses. We measure the effects of insulation usually on a thermograph; this shows us where and how much heat is escaping in our houses. On a well insulated house the thermograph will show up blue, green or yellow as there is not much infrared escaping and being detected on the device however if there is heat escaping the colors will be orange, red or even white. There are three main ways of which heat escapes from our houses. These are: Convection, Conduction and Radiation.

Convection only occurs in fluids (liquids or gasses). Particles in the substance get less dense as they heat up and move upwards replacing particles that are cooling down and getting more dense. This creates a cycle of moving particles.

Conduction occurs in all materials. It is the movement of energy through particles, as particles heat up they vibrate and collide with other particle they pass the energy onwards.

Radiation is direct heat transfer, it goes through all materials including vacuum. We can only reflect it back into the house.

In houses we use the following to prevent heat loss:

Loft Insulation, this traps air molecules and prevents conduction and convection.

Cavity Wall, this prevents conduction through gaps in the wall and also convection currents in the gaps of air molecules.

Double Glazed Windows, this traps air between two panes to stop conduction through the glass.

Draft Excluder, this prevents cold air from entering from the outside.

Radio Waves and Micro Waves are two different ways which we carry information. They both have different wavelengths. Microwaves have a shorter wavelength than radio waves. We use microwaves as the means of transport of information to our phones because the wavelength is shorter and when something with a shorter wavelength hits a gap between the top of a hill and the ionosphere it can bend, this is called diffraction. Radio waves don't spread out as much when they pass the gap so if you stand at the bottom of the hill you will be able to pick up microwave signals but not radio waves. The ionosphere is a layer of the earth's atmosphere which was created by the suns energy. It diffracts radio waves back towards the earth as…