Required practical

Aim

To investigate the variables that affect temperature changes in reacting solutions.

Apparatus

  • polystyrene cup
  • thermometer
  • 250 cm3 glass beaker
  • measuring cylinder
  • top pan balance

Context

You could investigate one or more chemical reactions, for example:

Method

Reacting two solutions, eg acid and alkali

  1. Place the polystyrene cup inside the glass beaker to make it more stable.
  2. Measure an appropriate volume of each liquid, eg 25 cm3.
  3. Place one of the liquids in a polystyrene cup.
  4. Record the temperature of the solution.
  5. Add the second solution and record the highest or lowest temperature obtained.
  6. Change your independent variable and repeat the experiment. Your independent variable could be the concentration of one of the reactants, or the type of acid/alkali being used, or the type of metal/metal carbonate being used.

Method

Reacting a solid with a solution, eg metal and acid

  1. Place the polystyrene cup inside the glass beaker to make it more stable.
  2. Measure an appropriate volume of the solution, eg 25 cm3.
  3. Measure an appropriate mass of the solid, or select a suitable sized piece of metal.
  4. Place the solution in a polystyrene cup.
  5. Record the temperature of the solution.
  6. Add the solid and record the highest or lowest temperature obtained.
  7. Change your independent variable and repeat the experiment. Your independent variable could be the surface area of the solid, or the type of acid being used, or the type of metal being used.

Analysis

The bigger the temperature change in the reaction, the more energy is absorbed or released. Remember that endothermic reactions absorb energy from the surroundings, and exothermic reactions transfer heat into the surroundings.

Evaluation

The biggest source of error in this experiment is unwanted heat transfer. Using a lid can help to reduce this.

Hazards, risks and precautions

HazardPossible harmPossible precaution
Dilute acids and alkalisMay irritate the skin or eyesAvoid contact with skin, rinse off skin if necessary, wear eye protection
Solutions of metal salts (used in displacement reactions)Dangerous to the environmentDispose of metal salt solutions as advised by teacher, some metal salts are collected for safe disposal rather than being poured down the normal drain