MYP-6: Experimental work

Growing salt crystals

Safety features

• Chemicals used in the laboratory are often impure and even apparently harmless substances may be toxic.
• Bunsen burners use flammable gas and must be handled with care

Apparatus needed:

• Test tube
• Clamp stand
• Dropping pipette
• bunsen burner
• Spatula
• Microscope and slide

Chemicals:

• Potassium aluminium sulphate
• Sodium chloride (common salt)
• Potassium nitrate
• Copper sulphate

Instructions:

1. Set up a water bath using a 400 cm3 beaker half full of water.
2. Measure out 5cm3 of water into a clean test tube and place the test tube in the water bath to warm up..
3. Add a spatula of the solute to be crystallised and if it all dissolves (with careful stirring) add more solute until some remains undissolved at the bottom of the test tube.
4. Allow any undissolved solid to settle at the bottom of the tube and withdraw a small quantity of the solution using a dropping pipette.
5. Place one drop of the solution on a microscope slide and watch for crystal formation through the microscope lens.
6. Draw the shape of the crystal produced.

7. If there is time repeat using different salts

key words

• solute
• dissolve
• solution
• water bath
• crystallise
• undissolved

When you have finished the experiment clean up your work area and write up the experiment