3. Heating Processes Flashcards
(22 cards)
What is the difference between solids, liquids and gases?
They have different amounts of energy
What is Specific heat capacity?
It is the amount of energy required to change the temperature of one kilogram of a substance by 1’C
E = m × c × θ
Energy transferred (Joules) = Mass (kg) x specific heat capacity x change in temperature
What is Specific Latent Heat of Vaporisation?
The amount of energy required to change the state of one kilogram of a substance from a liquid to a gas with no change of temperature
E = m x Lv
Energy (Joules) = Mass (kg) x Specific latent heat of Vaporisation
What is Specific Latent Heat of Fusion?
The amount of energy required to change the state of one kilogram of a substance from a solid to a liquid with no change in temperature
E = m x Lf
Energy (J) = Mass (kg) x Specific Latent Heat of Fusion
What is the link between temperature and infrared radiation emitted?
The hotter an object is the more infrared radiation it radiates in a given time
Dark, matte surfaces:
Good absorbers and good emitters of infrared radiation
Light, shiny surfaces:
Poor absorbers and poor emitters of infrared radiation
Good reflectors of infrared
What do U-values measure?
How good an insulator something is
The lower the U-value the better the insulator
How do solar panels work?
Solar panels may contain water, this water is heated by radiation from the sun, then it is used to heat buildings or provide domestic hot water
Energy:
Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed
What happens to wasted energy?
It is eventually transferred to surroundings, which become warmer
This energy becomes increasingly spread out and so becomes less useful
How can you represent energy flow in a system?
A Sankey diagram
Sankey diagrams:
Should be draw to scale
So the width of the ‘energy in’ arrow should equal the combination of all the ‘energy out’ arrows
How can heat energy be transferred?
Through convection and conduction
Through evaporation and condensation
Convection:
Liquids and gases expand when they are heated
The liquid or gas in hot areas is less dense than the liquid or gas in cold areas, so it rises into the cold areas. The denser cold liquid or gas falls into the warm areas. In this way, convection currents that transfer heat from place to place are set up.
Conduction:
Electrons free to carry charge move through lattices carrying electrical charge and heat energy
the rate at which an object transfers energy is determined by?
Its surface area and volume
The material it is made from
The nature of the surface with which the object is in contact with
The greater the temperature gradient…
The greater the rate of energy transfer
efficiency = useful power out / total power in
or
efficiency = useful energy out / total energy in
