Topic 1-Energy Flashcards
What is specific heat capacity?
The amount of energy requires to raise the temperature of 1kg of a material by 1°C
What is a closed system?
A system that experiences no net change in its total energy when energy transfers occur within it
What is the definition of ‘Power’?
The rate at which energy is transferred (or rate at which work is done)
What does it mean to say energy is dissipated?
Energy has spread out and become less useful
What is friction?
A force that opposes motion between objects in contact with each other
State 4 different stores of energy
Kinetic energy
Gravitational potential energy
Elastic potential energy
Chemical energy
Give examples of chemical energy stores
Food
Fuel
Batteries
State the law of energy conservation
Energy cannot be created or destroyed (it can only be transferred into different forms)
How can friction be increased?
Making the surface rougher
Adding a rougher material
How can friction be reduced?
Lubrication
Adding a liquid between the two surfaces
What is energy waste?
The energy that is not used by the device for its desired purpose
How can you reduce energy waste?
Lubrication
-Oil in a motor reduces friction so less energy is lost (as heat) through friction
Thermal insulation
-Double glazing means that less useful thermal energy is lost
What is thermal energy?
Heat
What causes thermal energy to transfer from one object to another?
If there is a difference in temperature between one object and another, thermal energy will move from the hotter object to the colder object until they are both at the same temperature
How does thermal energy transfer by conduction?
Heating a fluid (liquid or gas) causes the particles to vibrate with more kinetic energy. These vibrations are passed on from one particle to the next through the solid
How does thermal energy transfer by convection?
Heating a fluid (liquid or gas) causes the particles to move with more kinetic energy. The warm fluid becomes less dense and rises above colder areas of the fluid
How does thermal energy transfer by radiation?
Infrared radiation is electromagnetic radiation emitted by hot objects and absorbed by other objects
What colours absorb the most/least infrared radiation?
Black/dull surfaces are the best absorbers of infrared
Light/shiny surfaces are the worst absorbers of infrared
What colours emit the most/least infrared radiation?
Black/dull surfaces are the best emitters of infrared
Light/shiny surfaces are the worst emitters of infrared
What does it mean if a material is a good insulator?
The material does not allow thermal energy to pass through easily
How can the efficiency of a system be increased?
- Reducing waste output (lubrication, thermal insulation)
- Recycling waste output (absorbing thermal waste and recycling as input energy)
What key factors affect the rate of cooling of a building?
The thickness of the walls
The thermal conductivity of the walls
State three methods of reducing heat loss in a building
Double glazing
Loft and wall insulation
Thicker walls
How can the efficiency of a mechanical machine with moving parts be improved?
Lubricate any moving parts to reduce the friction and therefore energy loss due to heating
How can the efficiency of a radiator be improved?
Installing metal foil sheets behind the radiator to reflect the heat back into the room rather than it being absorbed into the walls
How can the efficiency of boiling water in a pan be improved
By placing a lid on the pan to reduce heat loss from the top
What is a renewable energy source?
An energy source which can be replenished as it is being used up and therefore will not run out
Give four examples of renewable energy resources
Wind energy
Hydro-electricity
Tidal energy
Solar energy
Give an example of a non-renewable energy resource
Fossil fuels (coal, oil and gas)
What are the advantages of generating power using gas rather than coal?
Flexible Generation: Gas power stations have short start-up times so can be switched on/off more readily
Lower emission of carbon dioxide
What is are some advantages of non-renewable energy?
Non-renewable energy is used for more large-scale energy supplies due to the large energy output per kilogram of fuel.
Renewable resources cannot provide such a large amount of energy as easily
Reliable. Not dependant on external factors so can generate power anytime
Still relatively abundant so cost-effective
Explain the environmental impacts of burning fossil fuels
Carbon dioxide contributes to the greenhouse effect, and causes global warming
Sulphur dioxide leads to acid rain, which can damage buildings and crops
What process is used to produce heat in nuclear power stations?
Nuclear fission
splitting atoms to release energy
What are some of the advantages of nuclear power?
Very large amounts of energy for relatively small quantities of fuel
Doesn’t release greenhouse gases and so doesn’t contribute to climate change
Low fuel costs
What are the disadvantages of nuclear power?
Produces radioactive nuclear waste which is harmful to humans and must be stored safely for centuries
Power stations are expensive to build and decommission
Risk of nuclear accidents, which have fatal consequences on humans and the environment
How does hydroelectric power produce energy?
Rainwater collects behind a dam
When this water is released from a high place (GPE -> KE), it is used to turn a turbine (KE->KE)
This turbine turns a generator which produces electricity (KE->Electrical)
What are the advantages of using hydroelectric systems to generate electricity?
Renewable
No atmospheric pollution at point of use
Low operating costs
What are the disadvantages of using hydroelectric systems to generate electricity?
Only suitable in certain areas (eg somewhere where a damn and reservoir can be built)
It can cost a lot to install the required infrastructure
The dam may cause flooding
Describe how geothermal energy can be used to generate electricity
Geothermal power stations use heat from below the Earth’s surface to heat water
This hot water can be used directly in heating systems or to produce steam to drive turbines and generate electricity
Describe how wave energy can be used to generate electricity
The motion of waves in the sea is used to move a floating generator up and down. This motion is used to generate electricity
Describe how tidal energy can be used to generate electricity
Water from each high tide is trapped behind a barrage/dam and then released past turbines
The turbines drive a generator to produce electricity
What are biofuels?
Biofuels are taken from living or recently living organisms
- Methane from animal waste
- Woodchip
- Vegetable oil/ethanol from sugar cane
What are some of the disadvantages of using biofuels?
-When plants are burned or decayed they release CO2
In order to grow biofuels, you need to destroy land which leads to problems because
- Naturals habitats
- May involve burning plants (CO2)
Growing biofuels reduces the land available for growing food
What are the advantages of tidal energy sources?
They do not produce greenhouse gases
They are quite reliable, as tides happen twice a day
They are cheap to run as tides are natural and so are free
What are some advantages of solar panels?
- They don’t cause harm to the environment
- They are a renewable resource
- They can be used in remote areas where other types of energy are less a accessible
What are some disadvantages of solar panels?
Expensive to produce
Inefficient
Lower power output
Cannot be stored and therefore may not be able to meet an always changing demand
What are some advantages of using wind to generate electricity?
Renewable
No atmospheric pollution at point of use
Low operating costs
What are some disadvantages of using wind to generate electricity
Only works when it’s windy
Low power output (you need hundreds to replace a power station)
Visual pollution
In addition to power input, light bulbs should also be labelled with the rate at which they emit visible light
Suggest why
Bulbs also transfer thermal energy
The efficiency of the light bulb also needs to be considered
Describe a method the student could use to investigate the insulating properties of newspaper
Wrap certain amount of layers of newspaper around the metal can
Heat water in can and put water into can
Use measuring cylinder to measure the volume of the water
Measure initial and final temp with digital thermometer
Use stopwatch to measure a time of 5 minutes
Calculate temp decrease then repeat with different numbers of layers
Use same initial temp and same volume of water
As a person moves down the zipwire her increase in kinetic energy is less than her decrease in gravitational potential energy
Explain why
Work done against air resistance creates thermal energy to be transferred to surroundings
Different people have different speeds at the end of the zip wire
Explain why
Different people have different surface areas so they would be affected by air resistance differently
Suggest some potential sources of random error
Variation in initial mass of ___
Variation in room temp
if with ice-ice melting while handling`
How do you correct a zero error after readings have been taken from the balance
Record the value of the zero error when there is no object on the balance
Take away the amount the zero error was from all the readings
Give two reasons why a hydroelectric power station is not able to meet an increase in demand
the variation in demand is
(much) greater than _____
demand remains high for longer
than __ hours
Give two environmental advantages of using a gas-fired power station to generate electricity compared with using a coal-fired power station.
• no sulfur dioxide released • doesn’t cause acid rain • no particulates released • doesn’t cause global dimming • less carbon dioxide released (per kg of fuel burned)
less global warming
A car driver sees a fallen tree lying across the road ahead and makes an emergency stop
The braking distance of the car depends on the speed of the car
For the same braking force, explain what happens to the braking distance if the speed doubles
Doubling speed increase the kinetic energy
Kinetic energy increases by a factor of 4
Work done by brakes to stop the car increases
Work done increases by a factor of 4
Work done is force x distance and braking force is constant
So if work done increases by 4 then the braking distance must increase by 4
Give one environmental advantage to turning off electrical appliances when they are not being used
Conserves fossil fuels
Less fossil fuels are burnt
Less greenhouse gas is produced
The speed of the miner at the bottom of the slide is much less than the calculated maximum possible speed
Explain why
Work is done
Against friction between miner and slide
Due to slide not being perfectly smooth
A bullet is fired horizontally.
In the short time it takes for the bullet to reach its target, its horizontal speed has fallen to 80% of its initial speed
Explain why the speed of the bullet decreases so quickly
Friction with air resistance is high at high speed
Give two reasons for taking repeat readings in an investigation
To calculate a mean
To spot anomalies
Reduce the effect of random errors
The fire in a stove uses wood as a fuel. The fire heats the matt black case of the stove
The air next to the stove is warmed by infrared radiation
How does the design of the stove help to improve the rate of energy transfer by infrared radiation?
Black is a good emitter of infrared radiation
It has a large surface area
Matt surfaces are better emitters than shiny surfaces
Some people heat their homes using electric heaters. other people heat their homes using a wood burning stove
Give two environmental advantages of using a wood burning stove to heat a home rather than heaters that use electricity generated from fossil fuels
Wood is renewable
Using wood conserves fossil fuels
Wood is carbon neutral
Give one advantage of using a temperature sensor and data logger instead of a glass thermometer to measure temperature
Greater sensitivity/precision
Could link to a computer for data analysis
More frequent readings
Reduces instrument error
Explain why the student recommended plastic foam and aluminium foil as the best insulator
Aluminium foil is a poor absorber of thermal radiation since it is light and shiny
Plastic foam traps air which is a good insulator
Explain, in terms of particles, how heat is transferred through the glass wall of a boiling tube
Particles vibrate with more kinetic energy/a stronger amplitude
Energy is transferred by collisions with other particles
A vaccum flask has:
- a plastic cap
- Double-walled glass container
- Vacuum
- Silvered surfaces
How do these features keep the liquid inside hot?
Plastic is a poor conductor and stops convection currents forming at the top of the flask so stopping energy transfer by convection
Glass is also a poor conductor so it reduces energy transfer by conduction
Vacuum stops energy transfer by conduction
Silvered surfaces reflect infrared radiation and are also poor emitters of infrared radiation
Instead they reflect the infrared radiation back towards the hot liquid partially.
It therefore stops energy transfer by radiation
Arctic foxes have small ears
How does the size of ears help to keep the fox warm in a cold environment?
The ears have a small surface area
So it reduces energy radiation/transferred from the fox
