In this lesson students learn the difference between combining materials and mixing materials and why each method produces different results. They should begin to understand how objects around them are formed.
Review an object that was investigated in Lesson 1 to review combining materials and the reason the materials have been combined. Restate that the materials are joined to make the object work better and that different materials can be identified.
Display some muesli and discuss the types of materials the students can see in the muesli.
Explain that the materials in the muesli are mixed together and this means they are fairly evenly spread. Add ‘mix’ to the science word wall. Compare again to combining.
State that mixing and combining are both very important in our lives.
- Display a ball of coloured playdough and invite students to explain if they think it is mixed or combined and what it might be made from. Recall that in the muesli we could still see the ingredients. Ask the students if they can see the ingredients in the dough. Why or why not? Display and label ingredients as identified.
- State that mixing affects materials in different ways depending on the properties of the material.
- Explain that in this lesson the students will investigate what happens when the different materials used to make playdough are mixed. They will record their observations in a table.
- Open the class science journal and model folding the page to create four columns. Rule a four-columned table with headings Material 1, Material 2, What do I see? and Notes.
- Model placing 2 level tablespoons of flour into a cup. Record ‘2 spoons’ and ‘flour’ in the ‘Material 1’ column. Tell students you are going to mix 1 level tablespoon of salt into the flour. Record ‘salt’ in ‘Material 2’ column.
- Ask students to predict what they think will happen and what the mixture will look like. Mix the ingredients. Invite a student to have a look and describe what they see. Model how to tip the mixture onto a piece of paper and flatten gently with your hand. Ask the student to look again and explain to the others what is seen now. Suggest how you might draw the mixture. Model a simple diagram of the flour and salt mixture in the ‘What do I see?’ column with a brief description in the ‘Notes’ column. Assure students they will get to see this when they do the activity themselves. See sample diagram below.
A diagram showing what we see when we make a mixture
- Explain to the students they will be investigating what happens to other playdough materials when they are mixed.
Teacher note: Full instructions for guiding students through the investigation ‘How do playdough ingredients mix’ can be found in Background information.
Regroup in front of screen/IWB. Show contents of one of the ice-cream dishes. Ask if it looks like playdough and what needs to be done to the dough. Display a cup half filled with water. Add a few drops of food colouring. Observe. Predict what will happen when you add the second colour. Predict what will happen when you add the colour to the playdough ingredients. Explain how it must be mixed more thoroughly by kneading.
Show the video clip Leisel Jones and Curtis Stone cooking coconut banana walnut bread.
Discuss how the ingredients in the banana cake mix together.