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You will perform various experiments in the chemistry laboratory. To do these experiments smoothly and efficiently, you must learn to handle properly different types of laboratory apparatus. These are shown in the figure and are briefly described below.

Matter can be changed from one form to another, e.g., ice (solid) on heating changes to water (liquid) and on further heating changes to steam (gas).

Matter is made-up of extremely tiny particles. These particles are so small that they cannot be seen even under most powerful microscope. These tiny particles are called molecules. A molecule is the smallest particle of a substance which can exist independently. John Dalton, in 1808 discovered that a molecule itself is made-up of still smaller particles called atoms. Thus, an atom is the smallest particle which makes matter. Modern researches have shown that even atom can be divided into electron, proton and neutron. Due to this reason, Dalton’s theory has been proved wrong. ARRANGEMENT OF MOLECULES Solids : In solids, the molecules are arranged compactly or closely packed. They have least intermolecular spaces. The force of attraction between the molecules is very strong and hence free movement of molecules is not there. Liquids : In liquids, the molecules are loosely held. There are large intermolecular spaces. The force of attraction between the molecules is less and hence free movement of molecules is there. Gas : In gases, the molecules are very loosely held. There are very large intermolecular spaces. The force of attraction between the molecules is least and hence the molecules move about freely. CHANGE OF STATE Heat results in weakening of the intermolecular forces of attraction thus, causing change of states. Solids have molecules packed tightly. When solids are heated, the heat energy is used to weaken the existing forces and hence separates the molecules, thereby forming a liquid state. When the liquid molecules are heated further, more heat further separates the molecules, thereby forming gaseous state. Heat even results in the expansion of solids. Most of the solids expand on heating as their molecular force of attraction decreases and atoms move away from each other.

Matter is anything that has mass and occupies space. Matter can exist in three states namely solid, liquid and gas. All the objects present around you such as, chair, table, pencil, pen, even your books are matter. This implies that, detailed knowledge of matter is very essential if anybody wants to understand the world around him. In our daily life, we come across a wide variety of things. All these things are materials. Some of these things are living and some are non-living. Living things include plants and animals whereas non-living include table, chair, pencil, pen etc. In general, all objects around us are made up of different kinds of materials. Therefore, we can say that, ‘all substances are composed of matter. ’

The idea that all substances contain incredibly small moving particles is called the kinetic theory of matter. The word ‘kinetic’ comes from a Greek word meaning moving. The main points of the kinetic theory are: (i) All matter is made-up of tiny, invisible, moving particles. These particles are actually atoms, molecules and ions. (ii) Particles of different substances have different sizes. (iii) Small particles move faster than larger particles at the same temperature. (iv) As the temperature rises, the particles possess more energy and move around faster. (v) In a solid, the particles are very close and they can only vibrate about fixed positions. (vi) In a liquid, the particles are further apart. They have more energy and they can roll around each other. (vii) In a gas, the particles are far apart. They move very fast and randomly in all the space they can find.