1
Why this material?
Workbook 2: Topic 3.3, pp. 35–37
GoalExplain that we choose a material because of its properties, using the word ‘because’.
New words
choose · to pick the best one for a jobuseful · good for a jobbecause · the word we use to give a reason
Explanation
People choose a material for a job by thinking about its properties. A bath towel is made of cotton, because cotton soaks up water. A saucepan is made of metal, because metal is strong and does not melt on a cooker. Rain boots are made of rubber, which keeps water out and bends when you walk. A fish tank is made of glass, so we can see the fish inside. We say: this object is made of this material because it is … Giving a reason is part of thinking like a scientist.
| Object | Material | Because it is |
|---|---|---|
| bath towel | cotton | absorbent |
| rain boots | rubber | waterproof |
| fish tank | glass | transparent |
Worked examples
Nodira’s umbrella is made of waterproof fabric. The rain runs off it.
Plastic is a good choice for a bucket. It keeps water in, and it does not crack when it is dropped.
Sara’s jeans are made of strong cloth. They do not tear easily when she plays.
Class activity
Look and say because (with an adult): walk round the kitchen and find five objects, such as a spoon, a cup, a tea towel, a window and a bin. Say what each is made of and give a reason, like “The spoon is metal because metal is strong.”
Practice
1
Why are a pair of glasses made with clear lenses?
Because the lenses must be transparent, so we can see through them.
2
Finish the sentence: A bath towel is made of cotton because cotton is ...
absorbent.
3
Why are rain boots made of rubber?
Because rubber is waterproof (and flexible).
4
Name one property of a strong material.
It does not break easily.