P1 - All Topics Flashcards
Why is it best to paint the outside of a metal cooking pot black?
Because black is a good absorber of heat. The heat will be used to cook the food.
Why does a cooking pot have a lid?
To reduce energy loss by convection.
Why is a car radiator painted black?
Black is a good emitter of heat, the heat is emitted to the surroundings to keep the engine cool.
Explain why thermal imaging cameras work better at night than during the day.
At night the surroundings are cooler so the surroundings emit less IR radiation than the warm body and this gives a clearer image.
What is the name given to heat transfer from particle to particle?
Conduction
What name is given to the heat transfer by the movement of hot liquids?
Convection
Why is the outside of a fire fighter’s suit shiny?
To reflect heat away from the fire fighter.
How is heat transferred through a metal?
Free electrons inside the metal gain kinetic energy and collide with the metal ions.
Why are radiators painted white and not black?
if they were painted black, they would transfer heat too quickly and the watertemperature inside theradiator would drop too quickly. The next radiator would then stay cold.
How does the Sun transfer heat?
Radiation
A bag is filled with water and placed in the Sun. What colour should the bag be so that the water can be warmed?
Black, as black surfaces are good absorbers and emitters of thermal energy. Heat from theSun is absorbed and used to heat the water.
Which methods of heat transfer are reduced by a vacuum?
Convection and conduction as both require particles.
which method of heat transfer is reduced by silver surfaces?
Radiation; heat is reflected
Which methods of heat transfer are reduced by plastic caps?
conduction as plastics are good insulators & convection
Why does a fridge have a white shiny surface?
A white shiny Surface is a poor absorber of heat and reduces heat transfer into the fridge. The heat is reflected instead.
how is energy transferred from the base of a sauce pan to the water inside the pan?
water particles at the bottom gain energy and move faster; the density of water decreases; hot water rises and is replaced by cold water
What is thermal radiation?
infra red radiation
Why does warm water freeze quicker inside a freezer than cold water?
The rate of heat transfer is greater with warm water.
why does 1kg of a gas have a larger volume than 1 kg of a solid?
There are strong forces of attraction between the particles in a solid holding the particles close together. In a gas the forces are very small so the particles can spread out.
Why does the temperature of a liquid decrease as the liquid evaporates?
the particles with most energy leave the liquid and the mean energy of the remaining particles decreases so the temperature goes down.
Why does sweating cool you down?
To evaporate the sweat requires energy which is taken from the skin/body.
How can you speed up evaporation?
Increase the surface area; use wind/draughts to allow particles with high energy to escape from the liquid
Describe the arrangement of particles in solids, liquids and gases.
In solids, particles vibrate around fixed positions. In liquids they are arranged in a pattern, in gases they move at high speed in any direction.
What is the ideal weather for drying clothes outside?
Warm/sunny and windy
<p>Define renewable energy</p>
<p>An energy source that is replaced faster than it can be used.</p>
Give examples of renewable energy sources.
Wind, waves, tides, hydroelectric, biofuel, geothermal, solar
How does the step-up transformer increase the efficiency of the National Grid?
It increases the voltage and decreases the current, therefore reducing energy loss along the cables.
Explain one effect burning fossil fuels has on the environment.
produces greenhouse gases, nitrogen oxides (trigger asthma attacks), sulphur dioxide (leads to acid rain)
Pumped storage hydroelectric power stations have a short start-up time. Why is this important?
to meet surges in demand/ start generating electricity in a short time
<p>Give an advantage of a pumped storage hydroelectric power station.</p>
<p>can store energy for later use/ renewable</p>
Using mainly wind turbines to supply electricity might cause fluctuations in the electricity supply. Why?
wind speeds fluctuate so turbines don’t generate electricity at a constant rate
Between 2002 and 2008 the amount of electricity used in the UK decreased. Suggest why.
energy efficient lighting used/ developed; increase in energy costs so people switch off more; ‘switch off’ campaign raises awareness of environment
Although gas boilers are very efficient, some energy is wasted. What happens to this waste energy?
it is transferred to the surroundings, becomes spread out; wasted as sound
Give a disadvantage of a large scale hydroelectric power station.
large areas of land flooded, homes and habitats destroyed
What is the National Grid?
system of cables and transformers
Why is transferring electricity directly to local homes more efficient than using the National Grid?
less energy is wasted as the cables used are shorter
A solar cell can be used to recharge a mobile phone. Suggest and explain one factor that would affect the charging time.
time of day, position of solar cell, angle of solar cell towards Sun, latitude, cloud cover, dust; all cause a change in light intensity
What are the advantages of using solar cells instead of fossil fuel power stations to generate electricity?
no air pollution, free resource, renewable, usable in remote areas, no need to connect to National Grid
Fitting a new hot water boiler costs £1800 but saves £200 per year. What is the payback time?
9 years
Explain why using an energy efficient light bulb rather than an ordinary light bulb reduces carbon dioxide emissions.
less electricity needs to be generated from power stations, less fossil fuel needs to be burnt
Give two advantages of burning wood instead of coal.
carbon neutral, renewable, conserves fossil fuel reserves
Why do wood burning stoves have a large surface area?
to increase the rate of energy transfer
Do you agree with the statement that ‘replacing old freezers with more energy efficient freezers’ benefits the environment?
y- less fossil fuels burnt as less electricity needed, so fewer greenhouse gases emittedn- old freezers must be dumped and there are hazardous chemicals inside them
