Heat that is either gained or lost at constant pressure
Enthalpy change (ΔH)
The amount of heat energy in kilojoules (kJ) taken in or given out when one mole of a particular chemical reacts
ΔH is positive
The reaction is endothermic (has gained heat)
ΔH is negative
The reaction is exothermic (has lost heat)
Calorimetry
The measure of heat flow
Heat capacity
The amount of heat needed to raise the temperature of 1 mole of a substance
Specific heat
The amount of heat needed to raise the temperature of 1 g of a substance
Calculating heat (q)
1. q = mc ΔT (for heat within a given state of matter)
2. q = mc x (for heat between two states of matter when temperature is constant)
m
Amount of substance
c
Substance's heat capacity
ΔT
Temperature change
c x
Heat of fusion (0/l) or heat of vaporization (l/g)
Heat of vaporization (l/g)
The heat required to transform a liquid into a gas at a constant temperature. It is the energy needed to break the intermolecular forces between the liquid molecules, allowing them to become a gas.
Heat of solution
The heat released or absorbed when a solute is dissolved in a solvent to form a solution. It can be either exothermic (releasing heat) or endothermic (absorbing heat), depending on the specific solute and solvent.
