Year 7Science

CURRICULUMINTO THE CLASSROOM • Independent Learning Materials

Unit 1: Lesson 4

Mixtures and substances — Investigating mixtures and substances

Science start up

Today you will:

†identify different mixtures including solutions.

There is some sediment

(solid) in the bottom.

Above is an image that shows two different mixtures.

Themixture on the right is known as a solution.

1. Make an observation from the image about the similarities and differences between these two mixtures.

DepartmentofEducation, TrainingandEmployment

Page1

Unit 1: Lesson 4

Learn

Today you will:

†understand that water is found naturally as a mixture

†identify the characteristics of pure substances and mixtures.

Exploring mixtures and substances

Water is found naturally as a mixture with many dissolved substances including minerals and gases. Water can be purified by removing the dissolved substances.

Mixtures are made up of particles of more than one type of substance, combined but not bonded together.

Apure substance is made up of only the one type of matter.

Asolution is a mixture of a solute and a solvent. Therefore, it is made up of at least two substances where one substance dissolves within the other, making it transparent.

Mixtures

Solutions

Page2

DepartmentofEducation, TrainingandEmployment

Unit 1: Lesson 4

2. Complete Experiment A — Making a mixture:

(Clean the teaspoon between measurements and experime a) Place a teaspoon of salt in a neat pile on a piece of

paper.

b) Place a teaspoon of sugar (preferably raw or brown sugar) in a neat pile beside the salt.

c) Now mix the pile of salt with the pile of sugar.

Did the two substances become one or just sit beside

each other? Look for the different pieces of salt and sugar!

This combined pile is a mixture as it is now made up of two different types of matter. Both the salt and the sugar are pure substances, but when combined make a mixture of pure substances. Mixtures can be separated and you will do this in the upcoming lessons.

d) Explain what you observed when you mixed the two substances above (salt and sugar).

3. Complete Experiment B — Making a mixture:

a) Place a teaspoon of salt in a cup.

b) Pour a tablespoon of oil into the same cup. c) Now mix the salt with the oil.

4. Complete Experiment C — Making a mixture:

a) Place a teaspoon of salt in a cup.

b) Pour a tablespoon of water into the same cup. c) Now mix the salt with the water.

DepartmentofEducation, TrainingandEmployment

Page3

Unit 1: Lesson 4

How do these experiments

differ from your first mixture?

Are they still mixtures?

5. Describe what you observed when you made each mixture.

Solutions and solubility

Asolute is the name given to the substance being dissolved in a solution, a solvent however is the name given to the substance doing the dissolving.

Dissolving is the process where the solute mixes with the solvent so the particles are no longer visible. More substances dissolve in water than in any other liquid. This is why water is considered a universal solvent.

Thesolubility of a substance is the degree to

which the substance will dissolve. A substance can be considered:

•soluble — where a large amount of solute will

dissolve (≥ 1g/mL)

•slightly soluble — where a small amount of solute will dissolve

•insoluble — where an extremely small amount

of solute will dissolve (0.1g/mL).

It is important to note that solutes dissolve differently in some solvents

In Experiment C, salt was the solute

dissolved in the solvent water to make a solution of salt

water.

Page4

DepartmentofEducation, TrainingandEmployment

Unit 1: Lesson 4

6. Complete the learning object Making Water Drinkable: Mixtures. Select the heading ‘Solubility’ and

complete to the first two screens (stop at the ‘To do’

section).

©State of Victoria (Department of Education & Training), 2000

a) Describe the solubility of sugar, iron oxide and wax in water.

b) List factors that alter the solubility of a substance in water.

7.Complete Sheet 6 — Solubility vs. temperature.

a) Complete the table from your solubility experiment.

Does temperature affect the level of solubility?

Water temperature (°C) / Amount of salt (teaspoons)
Cold from the fridge
Room temperature
Warm from the kettle

b) In your Science Journal, draw a column graph of your results

with temperature on the horizontal axis (x-axis) and amount of salt on the vertical axis

(y-axis).

DepartmentofEducation, TrainingandEmployment

Page5

Unit 1: Lesson 4

c) Looking at your results and the graph, draw a conclusion about the effect of temperature on solubility.

Reflection

8. Complete the table below by:

a) writing your own definitions of each term

b) listing three examples of a pure substance, a mixture and a solution in your household.

Pure substance / Mixture / Solution
Definition
Examples / E.g. Water or ice / E.g. Water & sand / E.g. Water & salt

HOT TIP:

Ifyou’re having any difficulties forming a definition, then use your

dictionary.

Next lesson you will investigate simple separation techniques and consider how Indigenous Australian peoples used separation techniques.

Page6

DepartmentofEducation, TrainingandEmployment