21 September 2014

Plastics : Science Ncert

Plastics : Science Ncert / Cbse Revision Notes

Plastics are polymers of long carbon chains. They consist of very long molecules each composed of carbon atoms linked in chains. Fossil fuels contain hydrocarbons (compounds containing hydrogen and carbon), which provide the building blocks for long polymer molecules. These small building blocks, called monomers, link together to form long carbon chains called polymers.

Plastics, Uses of Plastics, Cbse / Ncert Revision Notes

Depending on this physical property, plastics are categorized into two types: 
  1. Thermoplastics and 
  2. Thermosetting plastics.
Plastics that get deformed easily on heating and can be bent easily are known as thermoplastics.  PVC polythene, nylon, acrylic, celluloid and cellulose acetate are examples of thermoplastic. Plastics that, when moulded, cannot be softened by heating are called thermosetting plastics. Bakelite, melamine, vulcanised rubber, duroplast and epoxy resin are examples of thermosetting plastics.

Characteristics of plastics:
  • Do not corrode easily
  • Light in weight
  • Strong
  • Durable
  • Can be easily moulded into different shapes and sizes. 
  • Poor conductors of heat and electricity.

Uses of plastics:

Plastic has a wide variety of uses in our day to day life. Here are some of the areas where plastic items are used.

HOUSE HOLD: Special plastic is used in the making of cookware used in microwave ovens for cooking food. In microwave ovens, the heat cooks the food but does not affect the plastic vessel.Teflon coating is another plastic which is used in non-stick cook ware. Teflon is a special plastic on which oil and water do not stick.

HEALTH CARE: The packaging material of tablets, syringes, threads used for stitching wounds and doctor gloves etc are made of plastics.

TRANSPORTATION: The interior parts of a car like the dash board, and some other parts of helicopters and aeroplanes are made of plastic.

MISCELLANEOUS: Plastic is used in the making of computer parts, circuit boards, food processors, shavers and hair dryers.


Material that gets decomposed through natural processes, such as by the action of bacteria, is termed as biodegradable. For example, peels of vegetables, fruits, other food stuff, paper and pieces of clothes. And material that is not easily decomposed by natural processes is termed as non-biodegradable. For example, plastic, polythene covers, thermocol, etc.


Polythene bags are non-biodegradable and cause environmental pollution. They undergo a process known as photo degradation, in which they break down into smaller and smaller toxic particles. These particles contaminate soil and water and end up entering the food chain when eaten accidentally by animals like cows. Besides, polythene bags can choke cattle to death. Hundreds and thousands of whales, dolphins, sea turtles and other marine mammals die every year after consuming discarded polythene bags, mistaking them for food.

Carelessly thrown polythene bags are also responsible for the clogging of drainage systems in cities and towns. Plastics take several years to decompose.

Ways to reduce the use of plastic materials:

  • Reduce- Avoid the use of disposable plastic bags, instead make use of cotton or jute bags for shopping.
  • Reuse: Plastic items should be reused wherever possible.
  • Recycle: It is better to recycle plastic waste. Most thermoplastics can be recycled.