P1-Chapter 1 Energy Transfer By Heating Flashcards
Infrared Radiation
Electromagnetic waves between visible light and microwaves in the electromagnetic spectrum.
Emit
Give out radiation
How does the temperature of an object affect the rate at which it emits infrared radiation
The higher the temperature of an object the greater the rate at which it emits infrared radiation
What is a vacuum?
A vacuum is a region that does not contain anything at all, not even gas particles
Why are house in hot countries often painted white?
Houses in hot countries are painted white because white is the worst absorber of infrared radiation
Why are the pipes on the back of the fridge usually painted black?
Because black surfaces are the best emitters of infrared radiation
Absorber
A substance that takes in radiation
Reflector
A substance that reflects radiation
Emitter
A substance that gives out radiation
How is the arrangement of the particles in a liquid different from that in a solid?
The particles in a liquid are in contact with each other but are not held in fixed position like those in a solid
How is the arrangement of the particles in a gas different from that in a liquid?
The particles in a gas are much farther apart and move around much faster than those in a liquid
Why are saucepans often made of metal with wooden handles?
The metal base of the saucepan is a good conductor so heat is conducted quickly to the food in the pan. The wooden handle is a poor conductor so it prevents someone picking up the saucepan getting burnt
Why are materials that trap air good insulators?
Air is a poor conductor so materials that trap air are good insulators
Conduction
Transfer of energy from particle to particle in matter
Conductor
Material/object that conducts
Free electron
Electron that moves about freely inside a metal and is not held inside an atom
Insulator
Material/object that is a poor conductor
Why doesn’t convection occur in solids?
Convection does not occur in solids because the particles are held in fixed positions and not able to flow
Why does a fluid become less dense when it is heated?
A fluid becomes less dense when heated because it expands, so there is the same mass of material in a larger volume
Convection
Transfer of energy by the bulk movement of a heated fluid
Convection current
The circular motion of matter caused by heating in fluids
What effect would decreasing the surface area of a liquid have on its rate of evaporation?
Decreasing the surface area of a liquid would decrease the rate of evaporation
What effect would decreasing the surface area of a liquid have on its rate of condensation?
Decreasing the surface area would decrease the rate of condensation
Why does painting an object dull black maximise the rate of energy transfer?
Painting an object dull black maximises the rate of energy transfer, because dull black surfaces are the best emitters of radiation
Why does trapping air in small pockets minimise the rate of energy transfer?
Trapping air in small pockets minimises the rate of energy transfer because convection currents cannot be set up
The specific heat capacity of oil is 2100J/Kc how much energy is needed to raise the temperature of 1kg of oil by 1.c ?
2100x1x1=2100 J
The specific heat capacity of water is 4200J/Kc how much energy is needed to raise the temperature of 2kg of water by 1c ?
4200x2x1=8400 J
What is the equation for specific heat capacity?
E=MxCx0 E- is energy transferred J M- is mass KG C- is the specific heat capacity J/KG c 0- is the temperature change 'C
Why is fibreglass a good insulator?
Fibreglass is a good insulator because it contains trapped air
Why are the pipes that contain be water in a solar heating panel often painted black?
The pipes that contain the water in a solar heating panel are often painted black because black is the best absorber of radiation
What is the best colour for a central heating radiator, glossy white or dull black?
Dull black
Why does a solid have a fixed volume?
All the particles are held together in fixed positions
When a liquid evaporates, why is the average kinetic energy of the remaining molecules reduced?
The most energetic molecules leave the liquid, so the average kinetic energy of the remaining molecules is reduced
Which types of energy transfer involve particles?
Conduction, convection and evaporation involve particles
What happens to the rate of energy transfer between an object and its surroundings if the temperature difference between them is reduced?
If the temperature difference is reduced, the rate of energy transfer decreases
How does energy from the sun reach the earth?
Energy from the sun reaches the earth as radiation that travels through space
How does the colour of a surface affect the rate of conduction?
The colour of a surface has no effect on the rate of conduction
Why are gases poor conductors?
Gases are poor conductors because the particles are far apart
Why are metals the best conductors?
Metals are the best conductors because they contain free electrons
What is convection?
Convection is the movement of energy through a fluid by movement of the fluid itself
How does cavity wall insulation reduce energy transfer from a house?
Cavity wall insulation traps the air in the cavity pockets, so preventing convection currents from being set up
The specific heat capacity of water is 4200J/kg ‘c how much energy is needed to raise the temperature of 3kg of water by 4’c
The energy needed is 50,400 J
