Soluble Substances

• Soluble solids (solutes) can dissolve in water (solvent).
• The substances in solutions cannot be separated by sieving, filtering, hand sorting, settling or decanting.
• Some solutes can be recovered (separated) by evaporating the solvent (such as recovering salt from sea water).
• When substances dissolve, solute particles become dispersed in the spaces between the solvent particles.

• Ask learners if they can guess what a soluble substance is.

Answer:  A soluble substance will form a solution when it is mixed with water.

• Ask learners to give examples of soluble

Answers could include: sugar, salt, etc.

• Are the learners able to guess what an insoluble substance is?

Answer:  It is a substance that does not form a solution when mixed with water.

• Ask learners to give examples of insoluble

Answers could include: sand, mealie meal, curry powder, custard powder, etc.

• Present an overview of key terms used when talking about soluble substances by using PRESENTATION 2: Soluble substances.

• Learners complete the practical activity in WORKSHEET B: Soluble and insoluble mixtures.
• Explain to the learners how this worksheet will be assessed.
• Teacher to use WORKSHEET B: Memorandum to mark the learners’ work.

• Ask learners if they can remember what happened when they mixed peas or beans with sugar or sand. Can they remember what happened when they mixed the water and the oil together? Were they able to separate the materials after it was mixed?

How did they do it?

Answer:  sorting or sieving or decanting

• Show VIDEO CLIP 2: How to create an ocean in a bottle (2:11 min.).
• Challenge the learners to try the experiment at home.
• Ask learners if they think we will be able to recover sugar from a solution of sugar and water.
• Tell them that we will conduct a series of investigations to find out if sugar can be recovered from a solution of sugar and water.

• Learners complete the practical activity (scientific investigation) in WORKSHEET C: Scientific investigations – Can a solute be recovered from a solution?
• Assign experiments to learners (or groups of learners).
• Explain to the learners how this activity will be assessed.
• Teacher to use WORKSHEET C: Memorandum to mark the learners’ work.

• Show VIDEO CLIP 3: To Separate a Saltwater Mixture by Evaporation (1:30 min.).
• To expand learners’ understanding solutions as special mixtures, let them watch this VIDEO CLIP 4: Just Add Water 02 – Copper Sulphate(1:15 min.).