Temperature, heat capacity, latent heat, conduction, convection, radiation, gas laws · 18 terms
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A form of energy that flows from a hotter body to a cooler body due to a temperature difference.
Heat is energy on the move — it always flows from hot to cold, never the reverse spontaneously.
The measure of the degree of hotness or coldness of a body — related to the average kinetic energy of its particles.
Two objects in thermal equilibrium have the same temperature, even if one has more heat energy.
Kelvin = Celsius + 273. 0 K = absolute zero.
A physical property that changes measurably and reproducibly with temperature.
Length of mercury in a thermometer, electrical resistance, colour — all thermometric properties.
Examples: length of liquid column, resistance of a wire, EMF of a thermocouple, volume of gas.
The SI unit of temperature. 0 K is absolute zero — the lowest possible temperature.
K = °C + 273. Kelvin is always used in gas law calculations.
The quantity of heat energy required to raise the temperature of a body by 1 kelvin.
A large pot of water needs more energy to heat up 1°C than a small cup — larger heat capacity.
C = Q/ΔT. Different from specific heat capacity!
The heat energy required to raise the temperature of 1 kg of a substance by 1 kelvin.
Water has a high SHC — it takes a lot of energy to heat up. This is why the sea warms up slowly in summer.
Q = mcΔT. SHC of water = 4200 J/kg/K.
The heat energy required to change a substance from one state to another without a change in temperature.
Boiling water stays at 100°C even as you add more heat — the energy goes into changing state, not raising temperature.
L = Q/m for specific latent heat.
The heat energy required to change the state of 1 kg of a substance without a change in temperature.
Q = ml. Two types: fusion (solid↔liquid) and vaporisation (liquid↔gas).
The heat needed to change 1 kg of a substance from solid to liquid at its melting point, without temperature change.
Ice melting: stays at 0°C while absorbing energy to break the crystal structure apart.
The heat needed to change 1 kg of a substance from liquid to gas at its boiling point, without temperature change.
Steam burns are worse than boiling water burns — steam releases extra latent heat energy when it condenses on skin.
The transfer of heat energy through a solid by the passing of kinetic energy from molecule to molecule, without the molecules themselves moving.
A metal spoon left in hot soup gets hot at the handle — heat travels along the metal by conduction.
Metals are good conductors because free electrons can carry energy quickly.
The transfer of heat energy through a fluid (liquid or gas) by the physical movement of the fluid itself.
Hot air rises, cold air sinks — this circulation transfers heat throughout a room from a radiator.
Only occurs in fluids. Hot fluid is less dense, rises; cool fluid sinks.
The transfer of heat energy as electromagnetic waves (infrared), requiring no medium.
The sun heats the Earth across the vacuum of space — only radiation can travel through a vacuum.
All objects above 0 K emit radiation. Dark/matt surfaces are better absorbers and emitters.
The average solar energy hitting 1 m² of Earth's atmosphere every second. Value: approximately 1.35 kW m⁻².
This is the average value — varies slightly with Earth's elliptical orbit.
The heat energy transmitted per second through 1 m² of a material when the temperature difference between its two sides is 1 K.
Double-glazed windows have a lower U-value than single-glazed — they conduct less heat.
Lower U-value = better insulator.
For a fixed mass of gas at constant temperature, pressure is inversely proportional to volume. pV = constant.
Squeezing a sealed syringe: halve the volume, double the pressure.
pV = constant or p₁V₁ = p₂V₂. Temperature must be constant.
When a body is fully or partially immersed in a fluid, it experiences an upthrust equal to the weight of fluid it displaces.
A steel ship floats because it displaces a weight of water equal to its own weight.
Upthrust = weight of fluid displaced = ρVg
A floating body displaces a fluid equal in weight to its own weight.
A boat settles until the weight of displaced water exactly equals the boat's weight.