3.5 To determine the factors that affect the solubility of materials  (Page 3/3)

Conclusion:

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• Not all substances are equally soluble.
• Solubility depends on the type of substance.

ASSIGNMENT 16

Another experiment to show that not all substances are soluble.

Requirements: A glass of tap water

Cooking oil

A teaspoon

• Half fill the glass with water.
• Pour a small amount of oil onto the water.
• Stir the oil and water for a few minutes.

What do you observe?

1. What do you see?

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2. Where is the oil?

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3. Can oil be dissolved in water?

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4. What is the reason for your answer above?

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LIKE WATER OFF A DUCK’S BACK

We say this about people who are not overcome by their problems.

Water just rolls off a duck’s back.

The duck doesn’t get wet at all.

Ducks’ feathers are oily.

Water and oil cannot mix, that is why the water runs off the duck’s back.

Most aquatic birds have oily feathers.

Penguins and other sea birds become very heavy when they are covered with oil. This happens when the sea is polluted with oil. The birds will eventually drown.

To save them, the oil must be washed off their feathers with detergent.

When they have been washed they cannot be put straight back into the sea because they will be soaked and will get very cold.

The birds have to be looked after for two to three weeks until their feathers have regained the special coating of oil.

ASSIGNMENT 17

To determine how a solvent affects solubility.

Requirements: Water

Methylated spirits

Two glass flasks

Naphthalene flakes (or crushed mothballs)

• Place a small amount of water in one flask and a small amount of spirits in the other.
• Add a teaspoon of naphthalene flakes to each flask and stir.

What do you observe?

1. What happens?

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2. Can you explain why this has happened?

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3. Complete:

Naphthalene dissolves easily in _____________________ but does not

dissolve in ____________________.

REMEMBER:

In all the experiments, except the last one,

we have used only WATER as the solvent.

There are many other solvents that can be used,

like spirits, paraffin etc.

Assessment

Learning Outcome 1: Learners respond confidently to their desire to learn about natural phenomena; they investigate relationships and solve problems within the context of science, technology and the environment.

Assessment Standard 1.1: We know this when the learner plans investigations: helps to clarify focus questions for investigation and describes the kind of information which would be needed to answer the question;

Assessment Standard 1.2: We know this when the learner conducts investigations and collects data: conducts simple tests or surveys and records observations or responses;

Assessment Standard 1.3: We know this when the learner evaluates data and communicates findings: relates observations and responses to the focus question.