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26 Cards in this Set
- Front
- Back
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What is heat a measure of? |
Energy (J)
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What happens when a substance is heated?
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The particles gain kinetic energy and they move/vibrate faster
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What scale is heat measured on and why?
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An absolute scale because it cannot go lower than 0
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What is temperature a measure of?
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Hotness and the average kinetic energy of particles in a substance
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What is specific heat capacity?
What is the equation? |
The amount of energy needed to raise the temperature of a 1kg substance by 1 degree.
Energy = mass x shc x temperature change |
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How do substances boil?
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Heat energy makes particles vibrate/move faster until the forces of attraction are overcome and big bubbles of gas form
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How do substances melt?
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Heat energy makes particles vibrate/move faster until the forces of attraction are overcome and the particles begin to move around
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What is happening when there are flat spots on heating graphs?
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The temperature is not being changed because the energy is being used to break intermolecular bonds between particles to change the state of the substance
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What is specific latent heat?
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The amount of energy needed to change the state of a 1kg substance without changing the temperature
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What is the equation for specific latent heat?
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Energy = mass x specific latent heat
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What is the conduction of heat a process of?
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The process where vibrating particles pass on extra kinetic energy to neighbouring particles
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What does conduction occur in?
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Solids
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Why are metals good conductors of heat?
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They have free electrons. Heating them makes electrons move faster and collide with other free electrons transferring energy
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What does convection occur in?
When does convection occur? |
Fluids (liquids and gases)
When the more energetic particles move from the hotter region to the cooler region and take their heat energy with them |
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What happens when fluids are heated?
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They expand and become less dense
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What are convection currents?
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When warmer less dense regions rise and cooler, more dense regions sink
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Where does heat radition occur?
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Doesnt need a medium (occur in a vacuum)
Only occur in transparent substances |
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What does the radiation emitted/absorbed depend on?
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Surface colour and texture
- Matte black = good - White, smooth and shiny = bad |
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How do grills and toasters heat food?
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By infrared
Heat is absorbed by surface particles, increasing kinetic energy. Energy is then transferred by conduction/convection to the centre |
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How do microwaves heat food?
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By microwaves
Microwaves penetrate 1cm into water/fat molecules, increasing kinetic energy. Energy is conducted/convected to the centre |
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What is the equation for payback time?
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Payback time = initial cost / annual saving
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What is loft insulation?
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When wool is laid across the loft floor to reduce conduction through the ceiling into the roof space
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What is cavity wall insulation?
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When there is two layers of brick with air/form inside to reduce conduction/convection
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What is double glazing?
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2 laers of glass with a gap of air to reduce conduction
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What does a hot water tank jacket reduce?
What do thick curtains reduce? |
Conduction
Conduction and radiation through windows |
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What is draught proofing?
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Strips of foam/plastic around the doors and windows to stop hot air going out. Reduces convection
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