Matter And Its Properties

Properties Of Matter: Matter possesses several properties. However, we shall discuss a few as under

Diffusion: It is the process where molecule of a substance penetrates another substance. Ii is known to of a liquid. i.e. gases and liquids. For example, LPG when it leaks, its smell can be felt in the nearby air.

Evaporation and Sublimation: It is the phenomenon when a particle on the surface of a liquid or a solid acquires enough to overcome  the attractive forces that hold  it as part of the substance, it escapes and becomes a particle of vapour or gas. Wind, heat and surface area affect the rate of evaporation of a liquid. When such vaporisation takes place in solids, it is known as sublimation.

Cohesion and Adhesion: Cohesion refers to the force of attraction between molecules of the same substance, eg. the molecules of liquid water in a glans. However, the force of attraction between molecules of different substances is called adhesion, For example, a postage stamp can be affixed to paper by applying gum. Then the force of attraction between the gum and paper is known as adhesion.

Surface Tension: Molecules at the surface of a liquid feel a strong downward force of pull as they  have no liquid molecules above. Hence, as compared to other molecules inside the vessel, which experience equal forces of downward pull and upward poll, molecules at the surface feel very weak upward pull force and resultantly strong downward force. It results in the tendency of a liquid surface to constraint and occupy the minimum area possible. This is called surface tension. This tension makes the area of the free surface as small as possible and makes the liquid surface behave like a piece of stretched rubber.

Osmosis: Certain substances are porous to one material, but not to another. For example, water will diffuse through a thin slice of potato, but sugar molecules will not. A membrane of this sort is called a semi-permeable membrane. The selective diffusion through such a membrane is known as osmosis Osmosis plays an important part in carrying liquids through plants, and in the absorption of food and disposal of waste by cells in plants and animals. It explains how food passes through the walls of intestines, and also explains in part how sap is forced to the top of a tree.

Viscosity: If you stir some water in a glass with a spoon and then stop stirring, the water continues to swirl more and more slowly until it comes to rest. If you had stirred honey or treacle instead of water, it would have come to rest much more quickly. Internal friction in treacle or honey is greater than internal friction, or resistance to motion, in water. The Viscosity of a fluild is the property it possesses of resisting the movement of its various parts. Viscosity is the internal friction of a fluid.

Elasticity - Hooke's Law: A solid rubber ball can be squeezed, stretched, bent or twisted, it will still revert to its original shape when the distorting force is removed. This property, which enables it to accomplish this, is called elasticity. It is defined as the property of matter by which a solid requires a certain amount of force to distort it, and then tends to resume its original shape when the distorting force is removed. The force per unit area, which tends to distort the body, is called stress. The relative amount of distortion thus produced is called strain. The stress changes the distances between the particles, either pulling them farther apart or pushing them closer together. When the stress is removed, forces between the particles restore them to their normal spacing.

Other Properties of Solids: A number of other properties of solids, such as ductility, malleability. hardness and brittleness, depend on the type and arrangement of the elementary crystals. Ductility is the property that determines to what extent a solid can be drawn out into fine threads. Tungsten is an extremely ductile solid material. Quartz is another very ductile material. The property of malleability refers to the extent to which a material can be made into thin sheets. Gold is one of the most malleable of all solids. Resistance to scratching of a surface is called hardness. Diamond, corundum, and topaz are all very hard. A scale called Mohs Scale is used to indicate the degree of hardness of minerals. Brittleness refers to the tendency of a substance to crumble when subjected to a blow. A typical brittle substance is the familiar rock salt.