Paper 1 and 2 heat energy etc Flashcards
What is internal energy and what is it the sum of
The energy stored by the particles and is caused by their individual motion and positions and is the sum of the kinetic energy of all particles and the potential energy of all the particles
What does internal energy not include
Gravitational potential energy or kinetic energy caused by the motion of the whole substance
What happens to the internal energy when a substance is heated
The kinetic energy increases so the internal energy increases
What is the specific heat capacity
The amount of energy required to raise 1kg of material by 1 degree
What factors affect how much energy must be gained by an object as it’s temperature increases
Temperature increases
Mass, more energy needed
Materials, some need more energy than others
Specific heat energy equation
Energy= mass x specific heat capacity x temperature change
What’s specific latent heat and what does it depend on
The energy transferred to a substance when it changes state measure in J it depends on the mass of the substance and the state it is in
The energy calculated in specific latent heat
It’s the change in internal energy. Since the temp is constant during change of state, the kinetic energy stays the same but poten. ener increases as bonds are bulle daprt
Latent heat energy equation
Energy= mass x specific latent heat
What are the three processes that heat can be transferred
Conduction
Convection
Radiation
What is conduction
Particles that are very close together transfer heat energy as they vibrate
How do non-metals conduct
That atoms near the heat source gain kinetic energy and vibrate more. As they collide with neighbouring atoms, the energy is passed on
How do metals conduct
The outer electrons of metal atoms are not attached to any particular atom. They are free to move between the atoms
Why are gases poor insulators
The particles in a gas are too far apart for collisions to transfer energy effectively
What is the best insulator
A vacuum because there are no particles to collide and pass on the energy
Good insulating materials
Polystyrene
Foam
Fibre glass
Cotton wool
Why are wool and fibre glass good insulators
Because they have lots of trapped air which is a poor conductor
What are the best insulators
Materials with the lowest thermal conductivity
What happens to the particles when a fluid is heated
They gain energy and spread out decreasing the density
Convection can’t happen in…
Solids because the particles aren’t free to flow
Vacuums because there aren’t any particles to flow
What is infrared radiation.
The transfer of energy by electromagnetic waves e.g. the sun heats the earth by infrared radiation as there are no particles is space to transfer the energy
What is the best emitter of thermal radiation
Matt black
What’s the worst emitter of thermal radiation
Silver
Good emitters are also
Good absorbers
What’s a perfect black body
An object that absorbs all the radiation that hits it and doesn’t transmit any radiation. A black body is the best possible emitter
What happens to the intensity of the radiation if the temperature increases
It increases at every wavelength and the peak moves to a shorter wavelength (higher frequency)
What does the temperature of the earth depend on
The rate that light and infrared radiation from the sun are absorbed by the atmosphere or surface and are reflected back into space
the rate at which the earth emits radiation from its surface and atmosphere
Examples of convection
In a fridge, the freezer at the top cools air at top and cools food on the way down. The air is warmer at the bottom, this warm air rises creating a convection current
Convection current in house
Convection causes heat to be lost through the roof. Loft insulation helps to reduce this
What’s a thermograph
These images are taken using infrared radiation. the different colors show which parts are emitting more infrared
How does heat energy flow
Flows from a hot object to a cooler one
What happens to a filament lamp as it warms up?
It glows a dull red as it is emitting the red part of the visible spectrum as well as infrared. Then turns orange-red to white as it gets hotter
Why does the filament lamp change colour as it heats up
Because it emits more radiation at shorter wavelengths as it gets hotter
