Core practical

Making copper sulfate crystals

There are a number of ways that you could make copper sulfate crystals in Chemistry. This is an outline of the required steps to undertake one of these methods.

Aims

To investigate the preparation of pure, dry hydrated copper sulfate crystals starting from copper oxide.

Method

Apparatus required for the core practical involving copper sulfate
  1. place some sulfuric acid in a conical flask and warm it in a water bath
  2. add a spatula of copper oxide powder to the acid and stir with a glass rod
  3. continue adding copper oxide powder until it is in excess
  4. filter the mixture to remove the excess copper oxide
  5. pour the filtrate (the copper sulfate solution) into an evaporating basin
  6. heat the copper sulfate solution to evaporate half of the water
  7. pour the solution into a watch glass and leave to allow all of the water to evaporate

Results

Record the appearance of the copper sulfate crystals, including their colour and shape.

Analysis

Hydrated copper sulfate crystals should be blue and regularly shaped. Describe how your crystals compare to this description. Suggest an explanation for any differences.

Copper sulfate crystals
Copper sulfate crystals

Evaluation

Question

Explain why the sulfuric acid is warmed in a water bath in step 1.

Warm acid will react faster than cold acid, helping to make sure that all the acid reacts with the copper oxide.

Hazards, risks and precautions

It is important in this practical activity to use appropriate apparatus and methods. This includes the safe use and careful handling of substances and equipment.

Evaluate the hazards and the precautions needed to reduce the risk of harm. For example:

HazardPossible harmPrecaution
Sulfuric acidConcentrated acid is corrosive and damages skin and clothesUse dilute sulfuric acid
Boiling water bathSkin burnsEnsure the boiling water bath is stable
Hot copper sulfate solution spitting out during crystallisationDamage to eyes and skinWear eye protection and avoid standing over the hot apparatus