P1.1 Heat Transfer Flashcards
Describe the bonding, arrangement and motion of particles in solids, liquids and gases.
Solids - bonded, close together and vibrate.
Liquids - not bonded, close together and wriggle quickly.
Gas - not bonded, far apart and move very quickly in straight lines.
Describe the kinetic energy of particles in solids, liquids and gases.
Particles in solids have low kinetic energy.
Particles in liquids have medium kinetic energy.
Particles in gases have high kinetic energy.
Explain the energy transfer during evaporation.
When a liquid evaporates it removes heat energy from the surroundings.
As a liquid changes into a gas it takes heat energy from surroundings to give its particles more kinetic energy to become a gas.
Explain the energy transfer during condensation.
When a liquid is formed through condensation heat is transferred to the surroundings.
As a liquid is formed it provides energy to the surroundings resulting in its particles have less kinetic energy.
State the factors that increase evaporation.
Evaporation is greater at high temperature.
High air flow.
Large surface area.
State the factors that increase condensation.
Condensation is greater when there is high moisture content in the air.
Lower surface temperature.
Define specific heat capacity.
The specific heat capacity of a substance is the amount of energy required to change the temperature of one kilogram of the substance by one degree Celsius.
State examples of how heat can be reduced from buildings.
Loft insulation.
Cavity wall insulation.
Draft excluders.
Silver foil on walls and ceiling.
Define U - values.
Measures how effective a material is as an insulator.
The lower the U - value, the better the material is an an insulator.
What is infra-red radiation?
Electromagnetic wave.
What factor increases the amount of infra-red radiation?
The hotter a body is the more energy its radiates as infra-red radiation.
Describe how the external colour affects emission and absorption of infra-red radiation.
Dark, matt surfaces are good absorbers and good emitters of radiation.
Light, shiny surfaces are poor absorbers and poor emitters of radiation.
Explain how conduction occurs in non-metals.
Particles vibrate more when heated, thus vibration passes through bonds.
Explain how conduction occurs in metals.
Metals are good conductors because they contain free-electrons.
The free-electrons can miss out atoms, transferring the heat energy quickly.
Explain how convection occurs in a gas or liquid.
When the particles in a gas or liquid are heated they move quicker, the gas or liquid expands, becoming less dense and rises.
This produces a convection current.
