ACARA v9 CONTENT DESCRIPTION “recognise that materials can be changed physically without changing their material composition and explore the effect of different actions on materials including bending, twisting, stretching and breaking into smaller pieces”
Builds on sorting and naming everyday materials such as wood, cloth, dough and metal. Here we do things to them, bend, stretch, twist and break, and look at what changes and what stays the same.
Changing the shape, not the stuff
You can change a material in lots of ways. You can bend a stick, stretch some dough, twist a towel or break a biscuit. Each time, the shape or size changes. But the material it is made of stays exactly the same. Wood is still wood, cloth is still cloth. We call this a physical change.
Bend a stick
Push the middle of the bendy stick down. It curves. Let it go and it springs back straight.
When you let go, the stick springs back to straight. You changed its shape and then changed it back.
Stretch it and squash it
Soft things like dough or clay are easy to change. You can pull them tall or press them flat into all sorts of shapes. No matter what shape you make, it is still the same dough, and there is still the same amount of it.
Stretch and squash dough
Take a lump of soft dough. Pull it tall, or press it flat. The shape changes but it is the same dough.
Pulling and pressing make new shapes, but it is the same dough every time. The same amount is still there. You did not turn it into anything else.
Twisting winds it up
When you twist a towel you wind it up tight, like wringing out water. It looks different, but it is still one towel made of the same cloth. Untwist it and it lies flat again.
Twist a towel
Hold both ends of a towel and twist. The stripes lean over as it winds up.
Twisting winds the towel up, but it is still one towel made of the same cloth. Untwist it and it lies flat again.
Breaking makes smaller pieces
Breaking a biscuit gives you more pieces, and each one is smaller. But all the pieces together are still that one biscuit. Breaking changes the size of the pieces, not what they are made of.
Break a biscuit
Snap a biscuit into smaller pieces. There are more pieces now, but it is still the same biscuit.
One whole biscuit. Press Break it to snap it into smaller pieces.
The big idea
Bending, stretching, twisting and breaking all change how a material looks. The shape or size is different, but the material itself is the same as before. That is what makes these physical changes.
The shape changed, the material did not
Pick each action. The shape on the left keeps changing. The tag on the right never does.
Bending, stretching, twisting and breaking all change the shape. The tag on the right stays the same every time: it is still made of the very same material. That is a physical change.
Why this matters
Knowing that you can change a shape without changing the material helps you choose the right thing to make something. You can bend wire into a hook, roll dough into a ball or fold paper into a plane, and still know just what each one is made of.
Quick self-check
1. You bend a bendy stick into a curve. What is it made of now?
2. You squash a round lump of dough flat. How much dough is there now?
3. You break one biscuit into four pieces. What do you have?
4. Bending, twisting, stretching and breaking all change the...
5. Which of these is a physical change you can do to a material?