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P1

Revision for AQA GCSE P1 module
by

T Billimoria

on 7 July 2016

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Transcript of P1

P1
Solids, liquids and gases
have different amounts of:
-
kinetic energy
-
forces
between their particles
- vibrate about a
fixed position
OR
move freely
- in liquids the particles have a
range of different
kinetic energies

gases can be compressed
Rate of heat transfer
depends on..
the
temperature difference
the
material
the object is
made
from
the
surface area and volume

the
material
that the object is
touching

LARGE
surface area to volume ratio - cools down/heats up quickly (fast rate)
SMALL
surface area to volume ratio - cools down/heats up S...L...O...W...L...Y
desert fox vs arctic fox
- body size (SA to volume ratio)
- pale colour
large SA - increase rate of heat loss
Heat energy can be transferred by:
conduction
convection
infrared radiation
evaporation
Conduction in metals .......
.....particles gain kinetic energy
.....they vibrate faster
.....free electrons move
.....collide with other free
electrons and lattice ions
.....transfer the heat energy
along
Convection

only happens in liquids and gases....why?
when heated, the particles gain
kinetic energy
the particles move
further apart
(the liquid or gas
expands
)
which makes the liquid or gas
less dense

so it
rises



Infrared radiation...

an
electromagnetic wave

Matt black surface:
- good absorber
- good emitter
- poor reflector
Shiny silver surface:
- poor absorber
- poor emitter
- good reflector
Evaporation....the difficult one!
liquid particles have a
range
of different kinetic energies

some move quickly, some
move slowly

when a liquid evaporates, it
loses its fastest particles
(with
the most kinetic energy)

This means the
average kinetic energy
of the particles left behind is
lower
. So, the
temperature goes down (it feels cooler)


TRAPPED AIR
air is a BAD conductor
air is GOOD at transferring heat by convection
if air is TRAPPED in pockets, then the air can't move - this stops heat loss by convection
NEVER SAY
PARTICLES
EXPAND!!!!!
Heat loss in houses
- cavity wall insulation
- loft insulation
- draught excluders
- double glazing
- carpet
- thick curtains
U-values
The lower the U-value, the
BETTER
it is at insulating
Cost effectiveness and payback time are
DIFFERENT
cost-effectiveness - depends on the initial cost and replacement time (try calculating cost per hour)
payback time = cost of insulation
energy bill saving
Specific heat capacity
the
amount of energy
needed to raise the temperature of
1kg
of a substance by
1 degree celsius

E = m x c x θ

Radiators are filled with oil/water because they have a
high specific heat
capacity so they release a
large amount of energy

Storage heaters are concrete because they have a
high specific heat
capacity. So..they take longer to cool down
Generating electricity.....fuels
Gas
Coal and oil
Nuclear
coal and oil
easy to transport
concentrated energy source
burning produces CO and SO
2
2
uranium and plutonium
no polluting waste gases (CO and SO )
concentrated energy source
radioactive wasted produced - must be stored safely
could be an accident releasing radiation over a large area
expensive to decommission
2
2
natural gas
burning releases CO and SO
2
2
quick to start-up and switch off (start-up time)
fossil fuels
fossil fuels....
made from plants and animals that lived millions of years ago
Power stations
fuel
is burnt to
heat water
in the boiler...
water
turns to
steam
...
steam
turns the
turbine
...
turbine
connected to the
generator
...
generator
produces
electricity
...
sent through the National Grid.

in nuclear power, nuclear fission is used to heat the water
6 mark EVALUATE question could involve the advantages and disadvantages of different methods of producing electricity
BE PREPARED.....USE THE SPECIFIC KEY TERMS - NO 'FLUFFY' ANSWERS....
'Fluffy' banned
answers!
environmentally friendly
dangerous
expensive
free
cheap
key terms to use:

- burning releases CO which causes global warming
- burning releases SO which causes acid rain
- decommissioning costs
- building costs
- maintenance costs
- fuel costs
- safety costs
- transport costs
- storing radioactive waste
- destroys habitats for wildlife
- prevents shipping
- can use the land bridge as a road
- noise pollution
- visual pollution
- unreliable or reliable
- unpredictable or predictable
- start-up time
- concentrated energy source (small mass of fuel gives
a large amount of energy
- land can still be used for farming
- lack of suitable sites
- can be switched on quickly to meet demand
- ideal for remote locations
- electricity depends on the intensity of.....the wind/
tides/light etc

2
2
Transferring electrical energy

Most household appliances transfer electrical energy into other forms.
It is the amount of energy transferred per second
Power is the rate at which an appliance transfer energy (how quickly)
.

It is measured in watts or kilowatts.
60W light bulb transfers 60 joules of energy every second
Energy = power x time


J W s
kWh kW h
energy companies use units instead of joules. 1 unit is 1 kWh
cost = units (kWh) x cost per unit
Oil filled radiator vs fan heater
low operating cost
no noise
keeps a steady room temperature
one power setting
takes time to warm up
expensive to buy
two power settings
warms the room quickly
small
expensive to run
noisy
not even temperature throughout the room
possible 6 mark answer - compare them
Energy
There are 9 different forms of energy:
light
electrical
heat
sound
elastic potential
gravitational potential
chemical
kinetic (movement)
nuclear
energy can be.....
transferred (from one form into another)
stored

dissipated (spread out)
energy can never be created or destroyed....it can only be transferred from one form into another
An efficient device transfers a bigger
proportion
of energy into a useful form
All energy eventually transfers to the
surroundings
....
which get
warmer

The
closer the efficiency is to 1
, the more
useful
energy the device is transferring
The National Grid and transformers
step up transformers

step UP the voltage + REDUCE the current

to REDUCE the energy loss due to HEAT

step down transformers

step down the voltage

for consumer safety
Underground vs overhead cables?
Possible 6 mark question
2
2
possible 6 mark answer explaining
conduction, convection, infrared radiation, evaporation
Waves
Waves transfer
energy
from one place to another.

There are
two
types of waves
Transverse waves

Longitudinal waves
the oscillations are
perpendicular
to the direction of
energy transfer

the oscillations are
parallel
to the direction of
energy transfer
wavelength
: distance between one point and the next identical point on the wave (measured in metres, m)

frequency
: the number of waves per second (measured in hertz, Hz)

amplitude
: the height of a wave from the middle or equilbrium position (measured in metres, m)
wave speed = frequency x wavelength
v = f x λ

m/s Hz m
all waves can be reflected, refracted and diffracted
angle i = angle r

what happens if the ray is
shone along the normal?
Forming an image in a plane mirror
the image is always:
same
size
as the object
same
distance
behind the mirror as the object is in front
laterally inverted
(left is right)
virtual
(not made from real light rays. A virtual image cannot be projected onto a screen)
How would you go about drawing this ray diagram in the exam?
Refraction
Waves can
change direction

when they enter a more or

less dense
substance
When the ray enters the block it gets
slowed down
and moves
towards
the
normal.

When it leaves the block it
speeds up
and moves
away from
the normal.
Could you draw the normal lines on this picture

What happens if the ray is shone ALONG the normal?
Diffraction is when a wave gets
spread out
when passing a gap or obstacle

to get maximum diffraction the
GAP
must be the
SAME SIZE
as the
WAVELENGTH
Sound
sound is a longitudinal wave

sound is caused by vibration in a MEDIUM

an echo is when sound reflects
The
pitch
(high or low) is linked to the
frequency
of the sound

high pitch = high frequency
low pitch = low frequency

The
volume
of a sound is linked to its
amplitude


loud sound = large amplitude
quiet sound = small amplitude
The electromagnetic spectrum
all
transverse
waves
all travel at the
same speed
in a vacuum
have different
wavelengths
,
frequencies
and
energy


have an annoying song.......

Make sure you can list them in order of:
wavelength
frequency
energy

The only part of the spectrum we can see is visible light.


Some EM waves are used for communication:
Radiowaves are detected by
aerials
. When it is absorbed by the metal it creates an
alternating current
which has the same
frequency
as the radiowave
microwaves used in satellite communications and mobile phones
living cells contain water


water
absorbs
microwaves - this is how they cook food

The long-term effects of exposure to microwaves from mobile phones, or from phone masts is
UNKNOWN

visible light radiowaves microwaves
& infrared
Infrared radiation can cause
burns
....this is how toasters work
The Doppler effect
This happens in lots of waves, but is REALLY noticeable in sound
TV waves are radiowaves with a small wavelength
when the source of the wave moves
AWAY
from the observer, the wavelength
INCREASES
and the frequency
DECREASES

when the source of the wave moves
TOWARDS
the observer, the wavelength
DECREASES
and the frequency
INCREASES
In Light this effect is called red shift
Red shift
- increase in wavelength as it
moves away

Blue shift
- decreases in wavelength as it
moves towards
The further galaxies are away from us, the
faster
they are moving.... the
bigger
the red shift.

Red Shift supports the
Big Bang Theory
(the universe began from a very small initial point)
Cosmic microwave background radiation (CMBR)
electromagnetic radiation that fills the Universe
detected with a radio telescope
left over from early development of the universe
Big Bang theory is the only current theory that can explain CMBR
Right.....now for some practice questions
What eventually happens to all energy?
What does efficient mean?
An electric motor is used to raise a weight. When 60 J of electrical energy is supplied to the motor, the weight gains 24 J of gravitational potential energy. What is its efficiency?
What factors INCREASE
the rate of heat loss?
Explain how the arctic fox is adapted for its environment?
Why do motorcycle engines have 'fins'?
Why does a mouse find
it difficult to keep warm?
Compare the energy, forces and spacing
between the particles in solids, liquids
and gases
Describe conduction
in a metal rod
Describe convection
What is infrared radiation?
What surfaces are good emitters and
absorbers of infrared radiation?
Explain how evaporation
causes cooling
what is condensation?
list the ways that heat
loss in houses can be reduced
what does a U-value measure?
what is the definition of
specific heat capacity?
what are the units for specific
heat capacity?
A car engine is found to be 21% efficient. If the total energy supplied to the engine in a given time is 750 000 J, calculate how much of this is usefully transformed.
How much heat energy is needed to raise the temperature of a 2kg piece of lead by 250°C? The
specific heat capacity of lead is 126 J/kg°C

A 150 g potato cools from 100°C to 50°C. If the specific heat capacity of potato is 2000 J/kg°C how much heat does the potato loose?
What are the advantages and disadvantages of coal?
What are the advantages and disadvantages of wind power?
What are the advantages and disadvantages of hydroelectricity?
What are the advantages and disadvantages of nuclear power?
What are the advantages and disadvantages of solar power?
What are the advantages and disadvantages of wave and tidal power?
Name two nuclear fuels
What does decommissioning mean?
Which method of generating electricity
is the most expensive to decommission?
describes the stages in a
coal-fired power station
Which methods of generating
electricity can be increased if demand increases?
Compare a fan heater
with an oil-filled radiator
Why are night storage heaters
filled with concrete blocks?
If double-glazing costs £2,500 and saves
£100 a year. What is the payback time?
How much energy is transferred when
a 3kW heater is on for 2 hours?

If it cost 12p per unit, how much would the
heater cost over this two-hour period?

Describe the parts
of the National Grid
Define a transverse wave. Give
two examples of transverse waves
Define a longitudinal wave. Give
one example of a longitudinal wave
Draw a wave and label the
wavelength and amplitude
what do waves transfer?
What is the speed of a wave with a frequency
of 100 Hz and a wavelength of 2m?
Where would you see
compression and rarefraction?
what is the law of reflection?
Describe the image in a plane mirror
What is refraction?
What would you need for maximum diffraction of water waves through a harbour?
Why would you receive
a radio signal at the bottom
of a hill, but not a TV signal?
What is the same about all
the waves in the electromagnetic
spectrum?
list the EM waves in order of wavelength
list the EM waves in order of frequency
Which EM wave has the most energy?
What are radio waves used for?
what is infrared used for?
what are microwaves used for?
what is the range of wavelengths
in the electromagnetic spectrum?
what feature of a sound wave
determines its volume?
what feature of a sound
wave determines its pitch?
what is an echo?
what happens to the sound
from by a car as it moves towards
a person standing on the pavement
what happens to the sound
from a car as it moves away
from a person on the pavement
what is red shift?
The further away a galaxy is, the bigger
the red shift. What does this tell us?
What is CMBR?
What is the Big Bang Theory?
What is the evidence for
the Big Bang theory?











prevents carbon dioxide building up in the atmosphere

it is stored underground in old oil fields or gas fields such as those found under the North Sea
Carbon
capture
renewable methods of generating electricity
Full transcript