Introduction
- A mixture consists of two or more different substances/materials mixed together.
- In some mixtures, the different substances are still clearly visible after mixing. The substances in such mixtures can be separated by physical means such as sieving, filtering, hand sorting, setting and decanting.
Teacher Input 1
- Greet the learners.
- Ask the learners who of them drink coffee.
- Ask them to explain how they made the coffee: What ingredients did they have to put together to make a perfect cup of coffee.
Answer: Hot water, coffee powder, sugar, milk, etc.
- Ask learners if they know what we call a substance that consists of different materials that have been mixed together.
Answer: A mixture.
- Ask learners: Who can give a definition of a mixture?
Answer: A mixture is two or more different materials that have been mixed together.
- Present an overview of mixtures of materials by using PRESENTATION 1: Mixtures (1)
When you ask learners to give examples of mixtures in which the different substances are still clearly visible, have examples to show the class.
Reveal the different examples:
- peanuts and raisins
- dried fruit
- different coloured or types of sweets
- sugar and cinnamon mix
- water and oil (e.g. foam bath and bath oil mixture)
- Use PRESENTATION 1: Mixtures (1) to ask learners how they would separate different mixtures.
Learner Activity 1
- This is a practical activity.
- Acquire and prepare the following materials in advance:
- bag of split peas or dried beans
- bag of rice
- small packet of sugar
- clean white sand
- plastic spoons for scooping
- paper cups for mixing
- sieve
- Guide learners as they follow the instructions and complete WORKSHEET A: Making Mixtures – Solids.
- Explain to learners how this worksheet will be assessed.
- Teacher to use WORKSHEET A: Memorandum to mark the learners’ work.
Teacher Input 2
- Tell learners that we have now mixed solid materials.
- The ingredients we mixed had different sized grains.
- Ask learners: What did you learn from this?
Answers can include:
- when the grains are large enough, we can separate them by hand;
- when the grains are of different sizes, we can use a sieve (sifting) to separate them.
Show Video Clip 1: Methods of Separation: Sieving (0:34 min.).
- Show Video Clip 2 for enrichment purposes. Video Clip 2 explains how a mixture of salt and sand (both solid substances) can be separated using water.
- Show Video Clip 2: Separating mixture of salt and sand (6:52 min.).
Learner Activity 2
- Guide learners as they follow the instructions and complete WORKSHEET B: Making mixtures – Solids and liquids
- Explain to learners how this worksheet will be assessed.
- Teacher to use WORKSHEET B: Memorandum to mark the learners’ work.
Teacher input 3
- Tell learners that we have now mixed solid materials with a liquid.
- Ask learners: What did you learn from this?
Answers can include:
- It is more difficult to separate a solid substance from a liquid
- Sometimes we can separate a mixture of liquid and solids through filtering.
- Sometimes we are able to separate a mixture of liquid and solids through settling. Settling allow materials to stand for awhile so that they can separate by gravity.
- Show Video Clip 3 as an illustration of how to separate sand from water using the settling method.
VIDEO CLIP 3: To Separate a Mixture of Sand and Water (1:00 min.).
- Show Video Clip 4 as an illustration of how to separate sand from water using the filtration method.
VIDEO CLIP 4: Separating Mixtures – Filtration (3:35 min.).
Learner Activity 3
- Guide learners as they follow the instructions and complete WORKSHEET C: Making mixtures – Liquids.
- Explain to learners how this worksheet will be assessed.
- Teacher to use WORKSHEET C: Memorandum to mark the learners’ work.
Teacher Input 4
- Tell learners that we have now mixed two liquids: water and oil.
- Ask learners: What did you learn from this?
Answers can include:
- It is not easy to separate two liquids in a mixture.
- It will take a long time to separate two liquids.
- Sometimes we can separate a mixture of two liquids through decanting.
- Tell learners that it is possible to mix materials in many different combinations.
- In a mixture, the materials that have been mixed do not change, but they keep their individual properties.
- Sometimes it is possible to separate a mixture into the individual materials again.
- Present an overview of the nature and characteristics of mixtures by using PRESENTATION 2: Mixtures (2).
Learner Activity 4
- Guide learners as they follow the instructions and complete WORKSHEET D: Properties of mixtures – Match the columns.
- It is important to give learners opportunities to practice the skills of matching columns before this activity is used in tests and exams.
- Carefully explain to learners how to answer the worksheet. They must not draw lines, but rather write the number of the correct answer in column B in front of the letter in column A.
- Explain to learners how this worksheet will be assessed.
- Teacher to use WORKSHEET D: Memorandum to mark the learners’ work.
Learner Activity 5
- Guide learners as they follow the instructions and complete WORKSHEET E: Separating mixtures.
- It is important to give learners opportunities to practice the skills of matching columns before this activity is used in tests and exams.
- Explain to learners how this worksheet will be assessed.
- Teacher to use WORKSHEET E: Memorandum to mark the learners’ work.
Revision Activity 1
- Learners complete QUIZ 1.
- Guide learners on how to undertake this revision activity and how the quiz will be assessed.
- Teacher to use QUIZ 1: Memorandum to mark the learners’ work.
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