Solutions, suspensions, colloids and emulsions.

Watch the Echo demonstration of the different mixtures, record the results and answer the questions.

1. Add 0.5 gm of salt (NaCl) to a 50 ml beaker containing about 25 ml of water.

Swirl gently.

What happens to the salt crystals?

Is this a solution, suspension or colloid? Why?

2. Discard the salt water and this time add 0.5 gm of sand to 25 ml of water.

Swirl gently.

What happens to the sand particles?

Is this a solution, suspension or colloid? Why?

3. Discard the sand solution and place 25 ml of water in the beaker. Sprinkle 0.5 gm of gelatin on the surface. Swirl gently and then allow to stand for 10 minutes. Clean all glassware.

What happens to the gelatin?

Is this a solution, suspension or colloid? Why?

4. Mark a test tube at 2 cm and at 4 cm from the bottom. Fill to the 2 cm mark with vegetable oil and to the 4 cm mark with water. Use parafilm to cover tube and mix vigorously. Let the tube stand for 10 minutes Explain what happens.

5. Now add 2 drops of dishwashing soap to the test tube of water and oil and again mix vigorously. Let stand for 10 minutes.

Explain what happens.