Physics Unit 1 AQA GCSE (New Spec.)

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Preview of Physics Unit 1 AQA GCSE (New Spec.)

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Kinetic theory
The Kinetic theory describes the rate of movement in particles.
Substances can exist in three states of matter ­ Solid, Liquid and Gas ­ in each state the arrangement of particles is different.
SOLIDS: strong forces of attraction hold particles a fixed, regular arrangement giving
solid a definite shape. The particles don't have much energy so they vibrate around a
fixed point.
LIQUDS: Weaker forces of attraction between particles but particles can move around,
touching each other forming irregular arrangements. They have more energy than
particles in a solid - they travel in random directions at low speed
GAS: Almost no forces of attraction between particles ­particles have more energy
than liquids and solids; they are free to move at high speeds in random directions
colliding with each other and the walls of the container
Heat Energy Transfer
Heat flows away from a hotter object to its cooler surroundings. It can be transferred in three different ways ­
Infrared Heat Radiation the transfer of heat by infrared (IR) radiation (transmission of EM waves) without using particles
All objects continually emit and absorb infrared radiation at a temperature greater than absolute zero (-273.15°C) ­ the difference in
temperatures make heat flow
An object that's hotter than it's surroundings emit more IR radiation than it absorbs ­ an object that's cooler than its surroundings
absorbs more IR radiation than it emits
The hotter the object, the more radiation it emits in a given time
You can feel IR radiation if you stand near something hot, such as a fire.
Radiation can travel through a vacuum e.g. heat from Sun Earth
The rate of radiation depends on surface colour and texture:
- Dark Matt surfaces absorb and emit (at any given temperature) more heat radiation than light, shiny surfaces.
- Light, shiny surfaces reflect IR radiation falling on them ­ e.g. the silver lining of vacuum flasks keeping heat in or out of the
flask (depending on whether its storing hot or cold liquids)
- Hot solar water panels contain water pipes underneath a black surface (or black painted pipes under glass.) ­ Radiation from
the sun is absorbed by the black surface, heating water in the pipes ­ The water can be used for washing or pumped to
radiators in the house.
Conduction the process where vibrating particles pass on their extra kinetic energy to neighbouring particles
Thermal conduction is can transfer heat without the substance moving.
This process continues throughout a solid causing a rise in temperature at
the other side of a solid and an increase in the heat radiating from the
surface. Conduction happens in solids liquids and gases but is usually
faster in solids; because particles are closer together (denser) and so will
collide more often and pass more energy between them. Materials with
larger spaces (`air pockets') between particles, conduct energy much
slower, these materials are called insulators
Metals are good thermal (and electrical) conductors because of their free electrons unlike the ion cores that must stay in place. At the
hot end, the electrons move faster and collide with other free electrons, transferring energy to the other electrons etc. Because the
electrons can move freely, it is a much faster way of transferring heat energy than jostling neighbouring atoms. Conduction in metals is
more efficient in a short thin rod than a long fat one; it all comes down to the distance that the electros have to travel.
You'll notice that in, hot weather, if you touch the metal and wooden part of a spade the metal part feels hotter. They are both the same
temperature, it's just the metal conducts heat into your hand much faster than the wooden part of the spade. In cold weather, the metal
part of the spade feels colder than the wooden part, again, they are the same temperature, but the metal part conducts heat away from
your hand more quickly.
Convection occurs when the more energetic particles move from the hotter to the cooler region and take their energy with them.
Occurs in fluids (gases and liquids) due to the internal circulation of particles; it can't happen in solids because the particles
aren't free to move; examples include ­ immersion heaters, kettles, hot water tank, radiators heating up
a room, convection currents in the Earth's mantle and convection heaters.
The process ­ Saucepan Example
1) Heat energy is transferred from heat source (e.g. flame) to the water by
conduction through the bottom of the pan.

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Particles near the heat source get more energy and start moving faster, meaning that there's more distance between them i.e. the
water expands and becomes less dense. (Note that if there is water below the heat source, it will get hardly any heat by conduction)
3) The reduction in density causes the hotter water to rise above the cooler water. The hot water displaces the cooler water and
making the cooler water sink (towards the heat source).…read more

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There are many things that you can do to a
building to reduce the amount of heat that
escapes. Some are more efficient and some are
more cost effective.
Cost Effective are the methods which are the
cheapest; they have the shortest payback time
and cover the amount you pay really quickly.
Efficiency is the methods that give you the most
annual savings (they save you the most each
year on heating bills).…read more

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CHEMICAL ENERGY ­ possessed by batteries and food etc.
9) POTENTIAL ­ GRAVITATIONAL POTENTIAL ­ anything above the ground (e.g. book sitting on shelf) ­ ELASCTIC
POTENTIAL ­ stretched elastic band and springs have it
Potential and Chemical energy can be stored because it is energy that isn't obviously doing anything i.e. waiting for
something to happen and to be turned into other forms of energy.…read more

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Costing Electricity
Kilowatt-hours (kWh) are the units of electricity. The amount of energy transferred by an appliance depends on its power
(the rate it can transfer energy) and the amount of time that the appliance is switched on.
ENERGY (J) = POWER (kW) ÷ TIME (h)
COST (£ or p) = UNITS (kWh) X PRICE PER UNIT (£ or p)
E.g. "An electricity supplier charges 14 p per unit.…read more

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We use electrical energy the most because it is easy to covert into other forms of
energy (e.g. light, heat and sound0
- It is non-polluting at the point of use
Carbon capture and storage (CCS) can reduce the impact of CO2. It works by collecting CO2
before it is released into the atmosphere.…read more

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Because of the oil running out, many coal and oil-fires power stations are being replaced
by gas-fired stations ­ they're quick to set up and gas doesn't pollute quite as badly as
oil and coal. REMEBER THAT GAS IS NOT THE ONLYOPTION (see above)
The National Grid
Is a network of pylons, power cables and transformers that distribute electricity from
power stations to the country. To transmit a huge amount of power, you need either high
voltage or high current.…read more

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Waves transfer energy from one point to another without any matter (stuff)
Physically moving or being transferred between the two points"
Waves have:
AMPLITUDE: displacement from the rest position to the crest (central line to a peak)
WAVLENEGTH: length of a full cycle crest to crest (peak to peak)
FREQUENCY: the number of complete waves passing a certain point in a second, OR number of waves
produced by a source each second.…read more

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Displacement-distance graphs are different from displacement-time graphs ­ always check the x-axis
All waves can be reflected, refracted and diffracted.
1) Whenever a wave reaches an obstacle, the direction of the wave can be changed.
2) This can happen by reflection, refraction and diffraction
3) Note that the normal is always perpendicular to the mirror/other and is drawn with a dotted line
Reflection of light allows us to see things. Light bounces off objects and into our eyes.…read more

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The emergent ray is always parallel to the ...incident ray
- If the light wasn't travelling at an angle, the ...speed of the wave
would change and not the ...direction.
Electromagnetic Waves
EM waves with different wavelengths and frequencies have different properties. We group them into 7 different
types but actually there is a continuous spectrum of them.
Radio waves are waves with wavelengths longer than 10cm.…read more


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