or copper contain single atoms held together as their constituent particles whereas in some others two or more atoms combine to give molecules of the element. However, atoms of different elements are different in nature. These particles may be atoms or molecules.įor example, sodium, copper, silver, hydrogen, oxygen etc. (i) Elements: An element consists of only one type of particles. Pure substances can be further classified as (i) Elements (ii) Compounds Pure substances: A pure substance may be defined as a single substance (or matter) which cannot be separated by simple physical methods. They completely occupy the container in which they are placed.īased upon the composition, matter can be divided into two main types:ġ. Their movement is easy and fast.Ĭharacteristics of Gases: Gases have neither definite volume nor definite shape. Gases: In gases, the particles are far apart as compared to those present in solid or liquid states. Characteristics of liquids: Liquids have definite volume but not definite shape.ģ. Liquids: In liquids, the particles are close to each other but can move around. Solids: The particles are held very close to each other in an orderly fashion and there is not much freedom of movement.Ĭharacteristics of solids: Solids have definite volume and definite shape.Ģ. Matter can exist in three physical states:ġ. There are two ways of classifying the matter: For example, CNG (Compressed Natural Gas), a substitute of petrol, is very effective in checking pollution caused by automobiles.Ĭhemistry has played an important role in developing many industrially ^ manufactured fertilizers, alkalis, acids, salts, dyes, polymers, drugs, soaps,ĭetergents, metal alloys and other inorganic and organic chemicals including new materials contribute in a big way to the national economy.Īnything which has mass and occupies space is called matter.įor example, book, pencil, water, air are composed of matter as we know that they have Scientists are working day and night to develop substitutes which may cause lower pollution.
They are polluting environment at an alarming rate. Poisonous gases and chemicals are being constantly released in the atmosphere.
The rapid industrialisation all over the world has resulted in lot of pollution. (iii) A low concentration of chlorine i.e., 0.2 to 0.4 parts per million (ppm) is used ’ for sterilization of water to make it fit for drinking purposes. (ii) Disinfectants such as phenol are used to kill the micro-organisms present in drains, toilet, floors etc. Cisplatin and taxol have been found to be very effective for cancer therapy and AZT (Azidothymidine) is used for AIDS victims.
Today, dysentery and pneumonia are curable due to discovery of sulpha drugs and penicillin life-saving drugs. (i) It has provided mankind with a large number of life-saving drugs. (iii) The use of preservatives has helped to preserve food products like jam, butter, squashes etc. (ii) It has helped to protect the crops from insects and harmful bacteria, by the use ‘ of certain effective insecticides, fungicides and pesticides. (i) It has provided chemical fertilizers such as urea, calcium phosphate, sodium nitrate, ammonium phosphate etc. Some Basic Concepts of Chemistry Class 11 Notes Chapter 1Ĭhemistry has a direct impact on our life and has wide range of applications in different fields.
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