Energy Flashcards
State the law of conservarion of energy?
Energy camnot be created or destroyed, only transferred
Why do you need energy?
Breathe, move, grow
What are the 8 energy stores?
Chemical - objects
Thermal - heat
Kinetic- movement
Gravitational potential
Elastic - stretch, squash
Magnetic
Electrostatic
Nuclear
Desribe energy stores when cooking soup?
Cold soup - large chemical, small thermal
Hot soup - small chemical, large thermal
Describe energy storage in a torch?
Object is chemical
Converts to
Battery is electrical
Bulb is thermal
State unit of temperature vs unit of energy
Celsius / joules
State 4 pathways that transfer energy?
Conduction, convection, radiation and mechanical
How is energy transferred using conduction?
Molecules vibrate ( molecules themselves dont get warm) as they are delocalised/free to move about. These moving particles cause transfer of energy to the touching object
How is energy transferred during convection, eg radiator or soup in saucepan?
The source with the energy store (liquid or gas)heats up closest to the heat source moving from one location to another. Heat rises so the colder fluid/gas moves to the bottom replacing the hot liquid or gas in a current.
Why is metal a good conductor of heat?
Packed delocalised electrons.
What is a thermal insulator?
A substance that retains heat and is not a good conductor eg plastic, liquid, gas
How does a woollen jumper keep you warm in winter?
The jumper is made frim wool which is a good insulator as well as tge air trapped within the jumper. The body the temperature from our body is transferred to our clothing keeping the air and wool warm.
Name 3 fossil fuels?
Coal, oil, gas - formed millions of years Go from fossilsed remains eg sea creatures, trees. They are non renewable.
What does non renewable mean?
You cant use them again
What is radiation?
Transfer of energy by electromagnetic waves eg light, infrared, microwave
What is difference between transfer of energy of conduction/convection vs radiation?
Radiation doesnt need particles to transfer energy. Eg sun can travel through a vacuum.
Give examples of infrared radiation?
Burning coal, sun . All man made heated objects eg heated metal, electrical appliances. All objects emit infrared eg even an ice cube. All objects absorb infrared too.
State what happens when infrared hits a shiny surface?
They reflect infrared. Dark colours or matt objects absorb infrared more quivkly. Hang clothes out on the line and dark ones will be drier than light ones.
How would you slow down energy transfer using insulation? I can account for energy dissapation during transfers.
Conduction - use a good thermal insulator eg plastic kettle
Convection - use materials that can trap air
Radiation - use shiny surfaces to reflect heat
Disadvantage of using fossil fuels?
Coal create lots of carbon dioxide bad for environment (greenhouse gas) Other fossil fuels when burnt creates pollutants.
What is renewable energy?
Energy sources that do not run out, made ny scientists. Eg wind turbines, nuclear, turbines, biomass, solar, geothermal
How is electricity made from coal?
Coal is heated, which heats water to create steam, which spins the turbine. Turbine drives the generator to produce electricty. Chemical store of fuel is transferred to thermal energy.
What is the unit of power?
Watts ie how much energy is transferred per second.
How can you calculate power?
Power (w) = energy (kj) / time (s)
A shower has a power rating of 10 kilo watts (kwh). A family uses the shower for one hour per day? How much would they use in one week in kwh
10kw x 1 hour x 7 days = 70kwh
If 10 p per kwh, how much to use the shower? £7
How does conservation of energy apply to simple machines?
The easier the machine, the less energy / force required to use it eg using a screwdriver as a leverage to open a tin can ie force applied by the lever isgreater than force required by your hand
What is equation for doing work?
Work done/energy (j) = effort/power (n) x distance (m)
