Question: 1. Explain why some fibres are called synthetic. Answer: Some fibres are called as synthetic fibres because these are not obtained naturally, but are man-made fibres manufactured by using chemicals. These comprise of small units joined together to form long chains. Examples are PVC, rayon, Dacron, polyester etc. Question: 2. Mark the correct answer: …
Introduction There are some destructive natural phenomena like storms, cyclones, earthquakes and lightning. Human life and property get badly affected by these natural phenomena. But with time we evolved to protect our life from these types of destruction.
Introduction Materials such as iron, copper, and aluminium are known are conductors of electricity because they allow an electric current to pass through them. Materials such as rubber, plastic and wood are known as insulators or bad conductors of electricity because they do not electric current to pass through them. We can test the conductivity …
Class 8 Chapter 14 Chemical Effects of Electric Current Read More »
Introduction A great variety of plants and animals exist on earth. The part of the earth which contains living and non- living organisms is called Biosphere. It contains a huge variety of species living together that are interdependent on each other. The presence of a large number of organisms found in a particular area is …
Class 8 Chapter 7 Conservation of Plants and Animals Read More »
Combustion A chemical process in which a substance reacts with oxygen to give off heat is called combustion. The substance that undergoes combustion is said to be combustible. It is also called fuel. The fuel may be solid, liquid or gas. Sometimes, light is also given off during combustion, either as a flame or as …
Introduction Air, water, soil, coal, petroleum, natural gas and minerals are obtained directly from nature; therefore, they are known as natural resources. Plastics, synthetic fibres, steel, drugs, and explosives are all manufactured by man. Anything in the environment which can be used is called a resource. Natural resources can be broadly classified into two kinds: …
Introduction Fabrics are made from fibres obtained from natural or artificial sources. Fibres are also used for making a large variety of household articles. Natural fibres like cotton, wool, silk, etc., are obtained from plants or animals. Synthetic fibres, on the other hand, are made by human beings. That is why these are called synthetic …
