Materials
Fibres
A fibre is a piece of fabric that is long, thin and flexible. Plant fibres are the basis of febric such as cotton, silk and wool fibres come from animals.
Many artificial fibres have also been invented such as rayon, nylon, polyester, acrylic, etc.
- Rayon - is also known as 'artificial silk'. Cellulose which is obtained from wood pulp is the raw material to prepare rayon. It is used in home furnishings, suits, ties, blouses, sportswear, etc.
- Nylon - is entirely made of chemicals. It is very strong, elastic, light and water-resistant fiber. It is lustrous in appearance. It is used in making ropes, tents, fishing nets and parachutes.
- Polyester - is made from 'petroleum'. It is very strong, crease resistant, light, elastic and absorbs very little water. It is used in making pants, shirts, suits, jackets, etc.
- Acrylic - is made from a chemical called 'acrylonitrile'. Due to its wool like feel, acrylic fiber is often used as a substitute for wool. It is used for making sweaters, shawls, blankets, sportswear, socks, carpets, etc.
Plastics
A plastic is a synthetic material which can be moulded into desired shape when it is soft and then hardened to produce a durable article. For example, polyethene, PVC, Bakelite, Melamine and Teflon.
Types of Plastics:
- Thermoplastics - which can be moulded into different shapes again and again by heating. For example, polyethene, PVC.
- Thermosetting plastics - which cannot be moulded by heating. For example, bakelite and Melamine.
Metals
Metals are defined as elements which form positive ions by losing electrons. For example, sodium, potassium etc.
Physical Properties
- Good electrical conductors and heat conductors.
- They are malleable i.e. can be beaten into thin sheets.
- They are ductile i.e. can be stretched into wires.
- Possess metallic lustre.
- Opaque in nature.
- Solid at room temperature (except Hg).
Chemical Properties
- Usually have 1-3 electrons in their outer shell.
- Lose their valence electrons easily.
- Form oxides that are basic.
- Are good reducing agents.
- Have lower electronegativities.
Nonmetals:
Nonmetals are defined as elements which form negative ions by gaining electrons. For example, chlorine, oxygen, carbon, etc.
Physical Properties
- Poor conductors of heat and electricity.
- They are brittle.
- They are non-ductile.
- Do not possess metallic lustre.
- Transparent as a thin sheet.
- Solids, liquids or gases at room temperature.
Chemical Properties
- Usually have 4-8 electrons in their outer shell.
- Gain or share valence electrons easily.
- Form oxides that are acidic.
- Are good oxidizing agents.
- Have higher electronegativities.
