Unit 7 : Reduce,Reuse and Recycle
TIPS
- The material chosen to make to object depends on the properties of material. Example:
| Object | Required properties of material | Suitable material |
| Clothes | Absorbs sweat, soft | Cotton cloth |
| Medical glove | Can be stretched, waterproof | Rubber |
| Sampan | Floats on water | Wood |
- All material can be divided into two big group:
- Natural materials: clay, cotton, glass, leather, metal, paper, wool, wood
- Man-made materials: plastics, synthetic cloth
- Some natural materials are renewable but some are not. So, we need to conserve materials by reusing, reducing and recycling.
- Reusing means to use unused or waste materials again, either for the same or different purpose.
- Reducing means use less amounts of materials than usual.
- Recycling means reprocessing unused or waste materials into useful new products.
COMMON MISTAKES
The figure below shows a type of clothing worn in cold countries.
Which of the following materials is most suitable to make the clothing?
- Silk
- Nylon
- Wool
- Cotton
| Χ | Cotton is the most suitable material to make clothes. |
| √ | Wool is the most suitable as it can trap air in between its fibre. This makes wool an excellent heat insulator, thus preventing body heat from escaping to the cold surroundings. |
So, the correct answer is C.
