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  • Created by: haseeb786
  • Created on: 22-03-15 07:55

Heat & Temperature

A cup of coffee - 70 degrees celcius - energy stored within the liquid - the energy inside the cup will become the same temperature as the surroundings so the temperature drops.

Iced water - the hot energy outside will move into the cup - the ice will melt.

Thermogram - represents the amount of heat energy is emitted.

White in the thermogram is the hottest. 

More heat energy means more kinetic energy which increases the collision frequency.

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Specific Heat Capacity

Wooden spoon - warm in soup

Metal spoon - hot in soup

It takes more energy to raise the temperature of the wooden spoon - higher SHC


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Specific Latent Heat

The specific latent heat of fusion, l, of a substance is the heat needed to

(http://www.splung.com/heat/images/latentheat/phasechange.png)change a mass of 1 kg the substance from a solid at its melting point into liquid at the same temperature.

The phase change - period of latency - needed to break intermolecular bonds.


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Insulating your home

In a house, the heat goes: 

  • 25% to the roof
  • 35% to the walls
  • 10% to the windows
  • 15% because of draughts
  • Image result for roof insulation diagram gcse15% to the floors

Image result for roof insulation diagram gcse

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Insulating your home cont.

Payback time

The payback time of an energy-saving solution is a measure of how cost-effective it is. Here is the equation to calculate payback time:

payback time (years) = cost of installation (£) ÷ savings per year in fuel costs (£)

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Radiation & surfaces

A hot cup - you would feel heat coming away from the cup because of radiation - any hot object emits infrared radiation 

The hotter the object, the more infrared radiation is emitted

Thermogram - image of how much infrared radiation is emitted by an object

If the object gets hot enough, it may emit light. 

The Sun & the Earth - between the two is a vaccuum - radiation doesnt need particles because its an electromagnetic wave

Dull Black surfaces - absorb infrared radiation - thermal energy transferred - temp increased

Shiny silver surface - reflect infrared radiation - less heat transferred - less increase in temp

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Conduction & Convection


Frying pan - conduction - supplies heat from beneath the pan through the metal - metal is a good conductor of heat

As the heat increases, the particles collide so heat gets transferred to go through a material            - electrons gain heat and is transferred to each other                                                                  - this quickly increases the temperature

Wooden spoon - poor thermal conductor - good thermal insulator

Metal spoon - good thermal conductor - poor thermal insulator


  • Water cools - becomes denser - sinks                                   Conduction - SOLIDS
  • Water warms at the bottom - less dense - rises                     Convection - LIQUIDS & GASES
  • Convection current - continous cycle 
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Energy and efficiency

Light bulb - electrical energy in - 2 types of energy given out - light and thermal                              - useful energy is the light energy      - wasted energy is the thermal energy

(http://physicsnet.co.uk/wp-content/uploads/2010/08/efficiency-equation-3.jpg)    X 100

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Intro to Waves



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Intro to Waves cont.


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Total Internal Reflection

Angle of incidence

  • if the angle of incidence is less than the critical angle, the light refracts away from the normal
  • if the angle of incidence is equal to the critical angle, the light refracts at 90 to the normal
  • if the angle of incidence is greater than the critical angle - total internal reflection occurs

https://getrevising.co.uk/https_proxy/5944 (http://www.bbc.co.uk/staticarchive/65349aebb97d347429bfe1623d6ebd6cdb92d7f2.gif)

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Lights & Lasers

White light enters prism - spectrum - red light refracted least - blue light refracted most

Morse code - method of communication

Light travels incredibly quickly - useful, SOS messages transfer quickly

dashes and dots only - early digital signals - dot or dash

Lasers - produce narrow beam of light

light from one particular laser is one colour - surgery - dental treatments - CD DVD players

waves - same frequency - inphase - source of coherent monochromatic light - low divergence

CDs - surface has dips - dashes and dots  - laser beam shone across the surface - into the dip and internally refelected - signal there can be decoded.  Blu ray - more dips - better definition more data

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Cooking with waves

Conventional oven - infrared radiation - filament set on fire - when the door is closed, air inside the oven gets hotter, less dense rises. cooler air sinks. over time foods get hotter and hotter.

if food at the top - air touches surface of food - particles vibrate gain kinetic energy. black - good at radiating heat - silver foil relfects infrared to speed up cooking

Microwaves - 1cm into food - high energy - penatrate into food - fat or water

mircrowaves absored by fat or water molecuels - conductions occurs - cooks food from inside outside. white microwave so microwaves reflected into the microwave oven - cooking process quicker

microwaves can pass through glass and plastic - microwave door - thin lines of metal mesh - absorbs microwaves and stops causing you to burn.

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mobile phones - converting sound into microwave signal - sends to nearest phone and they can listen to you and talk to you

Transmitter sends out signal - cannot send a signal due to obstructions - buildings, hills

weather - rainy day - less bars of reception - microwaves are absorbed by water therefore reduced signal

the younger you are - thinner the skull - microwaves can go into your brain and it can affect it

younger children - 5 and 13 years - not to use mobiles as frequently as adults - water in the brain, absorb microwaves - potentially cause problems to the brain

curvature of the earth blocks line of sight. satellites used - one station - satellite - 2nd station

live broadcast - delay - has to be transferred to space and back into Earth

Ionosphere - layer of atmosphere - reflect and refract radio waves - lose signal quality - interference -signal muffled and quality of sound in a phone call affected severely

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Wireless Technology

Advantage - no wires needed - sends signal directly to laptop, computer, phone etc

portable and convenient - use on the move - allows access where we couldnt before

Disadvantages - difficulties with reaching it in different parts of the house - more walls - lower signal quality

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