2.9 Separation of mixtures

Natural sciences

Grade 8

Matter: classification

Module 22

Separation of mixtures

• Different methods of separation are used for different mixtures.

The educator will explain and may demonstratethe METHODS that are listed:

• Sorting by hand – sort according to size, form and colour
• Filtration – one of the substances is soluble
• Evaporation – dissolves in water and water evaporates leaving salts behind
• Separating funnel – two liquids with different densities
• Distillation – use a Liebig condenser to heat, evaporate and condense

APPARATUS:

Sketch of filtration and distillation apparatus and a separating funnel.

Activity: select a method of separation

Select and write down a method of separation for the following mixtures:

Sand and salt

Beans and peanuts

Squash syrup and water

Oil and water

Different coins

Assignment

Give a step by step explanation with sketches of the method you would follow to:

a) separate sand from salt.

b) separate squash syrup from water.

1. Which method would you use to obtain fresh water from sea water?

2. Why is this method not used to add to fresh water sources?

3. What is the difference between a distillate and a filtrate?

4. Explain what fractional distillation is and name two industries in which it is used.

Project

How would you separate water and alcohol?

• Also find out something about fractional distillation .
• Suggestion: use what you have found out about the boiling point of substances (learning unit 3).
• Sketches form an important part of a project !
• Submit the project on the date set by the educator.

Assessment of the project

Were you able to plan the project (AS 1.1), collect data (AS 1.2) and evaluate and communicate your findings (AS 1.3), as well as apply knowledge (AS 2.4)?

[LO 1.1; LO 1.2; LO 1.3; LO 2.4]

Assessment

Learning outcome 1: Scientific investigations

The learner will be able to act confidently on curiosity about natural phenomena, and to investigate relationships and solve problems in scientific, technological and environmental contexts.

ASSESSMENT STANDARDS: We know this when the learner

1.1 is able to plan investigations;

1.2 is able to execute an investigation and collect data;

• is able to evaluate data and communicate findings

Learning outcomes 2: Constructing science knowledge

The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

ASSESSMENT STANDARD: We know this when the learner

2.4 is able to apply knowledge.

Memorandum

Mixture Method

Sand&salt Filter

Beans&peanuts Manual sorting

Squash syrup&water Distillation

Oil&water Separating funnel

Different coins Manual sorting

Sketches – the correct apparatus

1. Distillation
2. Cost
3. Distillate – fluid condenses after distillation
4. filtrate – fluid that is filtered
5. filtering at different boiling points, e.g. at oil refineries and in the spirtis (alcohol) idustry.

PROJECT

Alcohol boils at 79ºC – fractional distillation removes alcohol; water is left behind.

Regulation of temperature, using a thermometer is very important.

Sketch of how the Lieg condenser is set up is important.