# P1 OCR Gateway Science GCSE Revision notes

My notes I made for my exam which I re-sited so these notes are quite detailed because I knew I had to do better (which I did :D ) but some may be brief because I could remember the section :) Hope it helps!!

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• Created by: Lucy :)
• Created on: 11-03-13 22:33

First 372 words of the document:

Heat =
Energy
absolute scale (not lower than zero (limit how slow particles can move))
Joule (J)
Temperature =
Hotness
Not absolute (can go below zero)
Energy hot cool objects
Difference in temperature, energy will flow
Greater dif ^ faster rate of cooling
Specific Heat Capacity
How much energy stuff can store
Amount of energy needed to raise temp by 1kg by 1oC
^ Water = 4200 J/kg/oC
Good for central heating systems ­ specific heat capacity is high
(for water) + liquid = easy to pump around house
Energy = Mass x Specific Heat Capacity x Temperature Change
Specific Latent Heat
Energy needed to change state
Specific Latent Heat of Melting = Amount of energy needed to melt 1kg
(without changing temp)
Specific Latent Heat of Boiling = Energy needed to boil 1kg (")
Specific Latent Heat = Dif for dif materials + dif for boiling and melting
Energy = Mass x Specific Latent Heat
Conduction
Occurs mainly in solids
-particles held tightly together
^ one vibrates bumps into others
^ kinetic energy moves from particles to particles
^ causes rise in temp at the other side
Conduction of heat is the process where vibrating particles pass on extra kinetic
energy to neighbouring particles.
Metals ­ electrons free to move = faster way of transferring energy
Non-metals - most = no free electrons- warm up slowly = good for insulating
Liquids and gases ­ conduct heat slower than solids ­ particles not so tightly together =
prevents bumping into each other so often = air good insulator
Convection
Occurs in liquids and gases
^heat = particles move faster ­ fluid expands = less dense
Warmer/less dense rises above cooler/dense surroundings
Warm fluid rises ­ cooler takes its place = circulation of fluid
Convection occurs when the more energetic particles move from the hotter region to
the cooler region ­ and take their heat energy with them
Convection not in solids as particles can't move ­ only
To reduce - need to stop fluid flowing
^ Clothes, blankets and cavity wall foam insulation ­ trap pockets of air

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­ has to conduct v.slowly through the pockets of air + material in between
Heat is radiated as infrared waves
Radiation is dif to conduction and convection:
Doesn't need a medium to travel through (can occur in a vacuum i.e. space)
Can only occur through transparent substances i.e. air, glass and water
Amount emitted or absorbed by an object depends to a large extent on its
surface colour and texture
Hotter object gets more heat radiation it emits

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Sankey Diagrams
Thickness of arrow represents the amount of energy
^ thicker the arrow = more energy
Wave Basics

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Refraction
Wave goes through dif density = change speed
Hit at angle = change direction
Electromagnetic Waves
Shorter wavelength = higher frequency
Increasing frequency and decreasing wavelength
^ = Gamma Rays

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Disadvantages: need to be close ­ IR beam from small, low-powered remote = fairly
weak, direct line of sight ­ IR waves only travel in a straight line
Good at long distances
^ don't get absorbed by atmosphere as much as middle EM or high-frequency end
Dif wavelengths refract and diffract differently
Long-wave radio ­ half-way round world ­ diffract around curved surface of Earth

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UV ­ damages DNA in cells = cancer
^cataracts
^premature skin aging
Darker skin = absorbs more UV radiation ­ prevents some of the damaging radiation from
reaching the more vulnerable tissues deeper in the body
Sun Protection Factor = SPF
^ SPF 15 = can spend x15 long as you otherwise could in sun without burning
Tanning salons now have time limits to reduce exposure
Ozone Layer