Materials Around Us

1What is a material?

Now here is the rule. A material is what a thing is made of. Wood, metal and paper are all materials.

A thing has a name. A material has a name too. The thing is a nail. The material is metal. They are not the same word.

2Materials you see every day

• Wood — it comes from trees. Chairs, doors, pencils.
• Clay — it is soil that has been made wet, shaped, and baked hard. Pots and jugs.
• Metal — it is dug out of the ground. Nails, spoons, hoe blades, coins.
• Cloth — it is made of thin threads woven together. Shirts, kitenge, blankets.
• Paper — it is made from wood too! Books, newspapers, boxes.
• Plastic — light and cheap. Cups, jerrycans, basins, bottles.
• Glass — clear, so light passes through it. Windows and bottles.
• Stone — hard, and heavy. Walls and roads.

3Sorting things by their material

Uwase lays six things out on the mat at home. She sorts them, one at a time. Watch how she thinks.

A pencil. Is it soft like cloth? No. It is a thin stick with grey in the middle, and it came from a tree. Wood.

A jerrycan. It is light. You can squeeze it a little. Plastic.

To sort anything, ask yourself one small question: what is this made of? Then put it with its friends.

4Test one: press it. Is it hard or soft?

Press your thumb into your desk. Push hard. Nothing happens. The desk does not change shape. So the desk is hard.

Now press your thumb into your sweater. It sinks in. It squashes. So the sweater is soft.

That is the test. Press it. If it keeps its shape, it is hard. If it squashes, bends or crumples, it is soft.

• Hard: stone, metal, glass, wood, a dry clay pot.
• Soft: cloth, cotton wool, a banana leaf, wet clay, a sponge, paper.

5Test two: slide your finger. Is it rough or smooth?

Slide your finger along a brick wall. It is bumpy. It scratches. The brick is rough.

Now slide your finger along a window. Your finger slips along easily. There are no bumps at all. The glass is smooth.

Slide your finger. If it bumps and scratches, it is rough. If it slides easily, it is smooth.

• Rough: a stone from the road, tree bark, a grass mat, an old brick.
• Smooth: a window, a metal spoon, a plastic cup, a shiny floor.

6These are two different questions

Here is where children get mixed up. Look carefully.

The window. Press it: it does not move. So it is hard. Slide your finger: it slips along. So it is smooth. The window is hard and smooth.

The brick. Press it: it does not move. So it is hard. Slide your finger: bump, bump, bump. So it is rough. The brick is hard and rough.

Both are hard. But one is smooth and one is rough! So hard does not mean rough. They are two separate questions, and you must ask both.

One more: your school shirt. Press it: it squashes, so it is soft. Slide your finger: it slips along, so it is smooth. Your shirt is soft and smooth.

Try it yourself

Say your answer out loud first. Then look below.

1. What material is a window pane made of?
2. What material is your exercise book made of?
3. You press a stone with your thumb. Hard or soft?
4. You slide your finger along a mat woven from dry grass. Rough or smooth?
5. Ishimwe says: "My plastic cup is hard. So it must be rough." Is he right?

7Answers

1. Glass. You can see straight through it, and light passes through.
2. Paper. And paper is made from trees, just like wood!
3. Hard. Press as hard as you like — the stone does not change shape.
4. Rough. Your finger bumps over the little grass strands.
5. No, he is wrong. Press the cup: it does not squash, so yes, it is hard. But now slide your finger: it slips along easily. So the cup is hard and smooth. Hard never means rough.

Now go and find three things at home. Say the material. Then press and slide.