AQA GCSE COMBINED SCIENCE
TRILOGY HIGHER TIER CHEMISTRY
PAPER 2H 10
◉ Convection longer definition. Answer: Unlike in solids, the
particles in liquids and gases are able to move. When you heat a
region of a gas/liquid, the particles move faster and the space
between particles increases. This causes the density of the region to
decrease. Because they can flow, the warmer and less dense region
will rise above denser cooler regions. If there is a constant heat
source, a convection current will be made
◉ Radiators - convection currents. Answer: Energy is transferred
from the radiator to nearby air particles by conduction. The air by
the radiator becomes warmer and less dense. This warm air rises
and is replaced by cooler air. At the same time, the previously heated
air transfers energy to the surrounding and cools, becomes denser,
and sinks. This cycle repeats and causes a flow of air to circulate
around the room
◉ How to reduce unwanted energy transfers. Answer: Lubrication
and thermal insulation
◉ Lubrication reduces frictional forces. Answer: When something
moves, there's at least one frictional force acting on it, causing some
,energy to be dissipated. For objects that are rubbed together,
lubricants reduce the fiction between the object's surfaces when
moved. Lubricants tend to be liquids (like oil) to flow easily between
objects and coat them
◉ Insulation reduces the rate of energy transfer by heating. Answer:
Things to do to prevent energy loss through heating...
- have think walls made from low thermal conductivity material.
This makes the rate of energy transfer slower, so the building will
cool more slowly.
- use thermal insulation
◉ Thermal insulation examples. Answer: - cavity walls made of an
inner and outer wall with an air gap in between to reduce the
amount of energy transferred by conduction.
- loft insulation can reduce convection currents created in lofts
- double glazed windows have an air gap between two layers of glass
to prevent energy transfer by conduction
- draught excluders around doors and windows reduce energy
transfers by convection
◉ Most energy transfers involve some waste energy. Answer:
Efficiency = useful output energy transfer / total input energy
transfer OR efficiency = useful power output / total power input
, ◉ Non renewable energy resources will one day run out. Answer:
Fossil fuels and nuclear fuels. Fossil fuels are typically burnt to
provide coal, oil, and natural gas. They damage the environment but
provide most of our energy
◉ Renewable energy resources will never run out. Answer: These
are: the sun, wind, water waves, hydro-electricity, bio-fuel, tides,
geothermal. Most of them do damage to the environment, but in less
nasty ways than non renewables. However, they don't provide much
energy and some are unreliable as they depend on the weather
◉ Energy resources can be used for transport. Answer: Non
renewable - petrol and diesel powered vehicles use fuel from oil.
Coal can be used in old fashioned steam trains to boil water for
steam.
Renewable - vehicles running on bio-fuels or a mix of a bio-fuel and
petrol/diesel.
Electricity sometimes powers vehicles and can be generated using
renewable or non renewable resources
◉ Energy resources can also be used for heating. Answer: Non
renewable - natural gas is widely used for heating homes. The gas
heats water, which gets pumped into radiators. Coal is commonly
burnt in fireplaces. Electric heaters use electricity generated from
non renewable resources.
TRILOGY HIGHER TIER CHEMISTRY
PAPER 2H 10
◉ Convection longer definition. Answer: Unlike in solids, the
particles in liquids and gases are able to move. When you heat a
region of a gas/liquid, the particles move faster and the space
between particles increases. This causes the density of the region to
decrease. Because they can flow, the warmer and less dense region
will rise above denser cooler regions. If there is a constant heat
source, a convection current will be made
◉ Radiators - convection currents. Answer: Energy is transferred
from the radiator to nearby air particles by conduction. The air by
the radiator becomes warmer and less dense. This warm air rises
and is replaced by cooler air. At the same time, the previously heated
air transfers energy to the surrounding and cools, becomes denser,
and sinks. This cycle repeats and causes a flow of air to circulate
around the room
◉ How to reduce unwanted energy transfers. Answer: Lubrication
and thermal insulation
◉ Lubrication reduces frictional forces. Answer: When something
moves, there's at least one frictional force acting on it, causing some
,energy to be dissipated. For objects that are rubbed together,
lubricants reduce the fiction between the object's surfaces when
moved. Lubricants tend to be liquids (like oil) to flow easily between
objects and coat them
◉ Insulation reduces the rate of energy transfer by heating. Answer:
Things to do to prevent energy loss through heating...
- have think walls made from low thermal conductivity material.
This makes the rate of energy transfer slower, so the building will
cool more slowly.
- use thermal insulation
◉ Thermal insulation examples. Answer: - cavity walls made of an
inner and outer wall with an air gap in between to reduce the
amount of energy transferred by conduction.
- loft insulation can reduce convection currents created in lofts
- double glazed windows have an air gap between two layers of glass
to prevent energy transfer by conduction
- draught excluders around doors and windows reduce energy
transfers by convection
◉ Most energy transfers involve some waste energy. Answer:
Efficiency = useful output energy transfer / total input energy
transfer OR efficiency = useful power output / total power input
, ◉ Non renewable energy resources will one day run out. Answer:
Fossil fuels and nuclear fuels. Fossil fuels are typically burnt to
provide coal, oil, and natural gas. They damage the environment but
provide most of our energy
◉ Renewable energy resources will never run out. Answer: These
are: the sun, wind, water waves, hydro-electricity, bio-fuel, tides,
geothermal. Most of them do damage to the environment, but in less
nasty ways than non renewables. However, they don't provide much
energy and some are unreliable as they depend on the weather
◉ Energy resources can be used for transport. Answer: Non
renewable - petrol and diesel powered vehicles use fuel from oil.
Coal can be used in old fashioned steam trains to boil water for
steam.
Renewable - vehicles running on bio-fuels or a mix of a bio-fuel and
petrol/diesel.
Electricity sometimes powers vehicles and can be generated using
renewable or non renewable resources
◉ Energy resources can also be used for heating. Answer: Non
renewable - natural gas is widely used for heating homes. The gas
heats water, which gets pumped into radiators. Coal is commonly
burnt in fireplaces. Electric heaters use electricity generated from
non renewable resources.
