Practical: Investigating Temperature Changes

Purpose of experiment

Measure temperature changes to identify exothermic or endothermic reactions

Typical reactions tested

Neutralisation, displacement, dissolving salts

Equipment

Polystyrene cup, lid, thermometer, measuring cylinder, stirrer

Why polystyrene cup

Good insulator, reduces heat loss

Why use lid

Minimises heat loss and evaporation

Why stir

Ensures even temperature throughout solution

Initial temperature step

Measure temperature of first solution before mixing

Mixing step

Add second reactant quickly and replace lid

Recording step

Measure highest or lowest temperature reached

Temperature change calculation

ΔT = final temperature − initial temperature

Exothermic sign

Temperature increases (positive ΔT)

Endothermic sign

Temperature decreases (negative ΔT)

Control variables

Volume of solutions, concentration, starting temperature, insulation

Sources of error

Heat loss to surroundings, inaccurate thermometer reading, slow mixing

Improving accuracy

Better insulation, use lid, use digital thermometer, mix quickly

Graph use

Plot temperature vs time to find true maximum/minimum temperature

Key idea

Temperature change indicates reaction type and allows energy calculations