Heat energy flows from a hotter body to a colder body. When energy flows away from a warmer object the temperature of the object decreases.
A thermogram uses colour to tell the temperature:
- hottest- white/yellow
- coldest- dark/black or blue/ purple
Temperature is a measurement of hotness on an arbitary scale. Temperature is measured in ºC (Degrees).
Heat is a measurement of internal energy or thermal energy on an absolute scale. Heat is measured in J (Joules).
When the temperature of a body increases, the average kinetic energy of the particles increases.
When heat energy is transferred to an object, its temperature increase depends upon;the mass of the object, the substance the object is made from,the amount energy transferred to the object.
For a particular object, the more heat energy transferred to it, the greater its temperature increase.
Specific Heat Capacity
Specific Heat Capacity (SHC) is the energy needed to raise the temperature of 1 kg by 1ºC.
When an object is heated and its temperature rises, energy is transferred.
The formula for SHC:
energy transferred = mass x SHC x temperature change (J or kJ) = (kg) x (J/kgºC) x (ºC)
SHC differs for different materials.
J= Joules kJ= kiloJoules kg= kilograms ºC= degrees celsius
When a substance changes state (e.g melting, boiling or freezing) there is no change in temperature. This is because energy is needed and being used to break the bonds that hold the molecules or particles together in a substance.
Specific Latent Heat
Specific Latent Heat (SLH) is the energy need to melt or boil 1kg of a material.
Latent heat of fusion is melting a material.
Latent heat of vaporisation is boiling or evaporating a material.
energy transferred = mass x SLH (J or kJ) = (kg) x (J/kg)