Calorimetry

Calorimetry definition

Method used to measure energy changes in reactions

Purpose of calorimetry

Determine whether reaction is exothermic or endothermic and calculate energy change

Temperature change meaning

Increase = exothermic, decrease = endothermic

Basic calorimetry setup

Thermometer, insulated container, known mass/volume of solution

Why insulation is used

Reduces heat loss to surroundings

Why lid is used

Minimises heat loss and evaporation

Combustion calorimetry

Burn fuel under a metal can of water and measure temperature rise

Energy transferred equation

Energy = mass × specific heat capacity × temperature change

Symbol equation

𝑞 = 𝑚 ⋅ 𝑐 ⋅ Δ𝑇

Specific heat capacity of water

4.18 J/g°C

Mass in equation

Mass of water being heated

ΔT meaning

Final temperature – initial temperature

Sources of error in combustion calorimetry

Heat lost to surroundings, incomplete combustion, heat absorbed by can

Improving accuracy

Use draught shield, lid, copper calorimeter, place flame closer to can

Solution calorimetry

Measure temperature change when reactants mix in insulated cup

Polystyrene cup use

Good insulator, reduces heat loss

Stirring reason

Ensures even temperature distribution

Energy change per mole

Divide energy transferred by moles of limiting reactant

Sign convention

Exothermic = negative ΔH, endothermic = positive ΔH

Key idea

Calorimetry measures temperature change to calculate energy change in reactions