CBSE Chemistry | Matter and its classification

Matter and its classification

MATTER:

Any thing that has weight and occupies space and can be felt by one of our senses is called matter e.g., air, water, wood, chalk, table, chair etc.

CLASSIFICATION OF MATTER:

(i) Based on state (Physical Classification)

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(ii) Based on purity/composition (Chemical Classification)

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. (iii) According to Ancient Indian Philosophers:

They classified matter in the form of five basic elements – The Panch Tatva”, i.e., Air, Earth, Fire, Sky and Water.

(iv) According to Greek Philosophers:

They believed that there were four basic elements, i.e. Earth, Fire, Air and Water.

PHYSICAL NATURE OF MATTER:

Every substance has a unique set of property. The properties of matter can be categorized as physical or chemical.

Physical properties can be measured without changing the identity and composition of the substance. These properties include colour, odour, density, melting point, boiling point and hardness.

Chemical properties describe the way of substance which may change or react to form other substances.

A common chemical property is flammability, the ability of a substance to burn in the presence of oxygen. Matter is made up of very small particles called atoms or molecules.

CHARACTERISTICS OF PARTICLES OF MATTER:

(i) Particles of matter have space between them,

(ii) Particles of matter are continuously moving,

(iii) As temperature rises particles of matter move faster.

STATES OF MATTER:

Matter can exist in three states

(1) Solid

(2) Liquid

(3) Gas

SOLID STATE:

In solids, particles are bound together by forces strong enough to prevent movement of translation. So that a solid has a definite shape which remains fixed (in constant conditions) unless sufficient force is supplied to shatter or distort the mass.

Particles in a solid may however, show a certain amount of movement of vibration.

Various particles involved in solids are (a) atoms (b) molecules (c) ions.

CHARACTERISTICS OF SOLIDS:

(i) solids have a fixed shape.

(ii) solids occupy a fixed volume.

(iii) solids can not be compressed.

(iv) solids have a higher density as compared to liquids and gases.

LIQUID STATE:

Liquid state of matter is the intermediate state between the gaseous and the solid state. This state arises when the molecules of the matter are held together by strong intermolecular forces in comparison to those in gases.

CHARACTERISTICS OF LIQUIDS:

(i) This state is characterized as having fluidity low compressibility.

(ii) Liquids have no definite shape or boundaries. They take the shape of container. Liquids have a definite volume.

(iii) Liquids generally have lower densities as compared to solids,

(iv) Liquids are more compressible as compared to solids.

(v) Liquid shows the property of diffusion.

(vi) Particles of liquids have more kinetic energy than those of solids.

GASEOUS STATE:

Gaseous state is the simplest state of matter which is observed when the boiling point of the substance is below the room temperature at atmospheric pressure. The forces of attraction between the molecules is minimum and hence the molecules are far apart from each other and thus their position is not fixed in gaseous state.

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CHARACTERISTICS OF GASES:

(i) Gases have neither a definite shape nor a definite volume.

(ii) They take the shape of the container in which they are stored and fill the container fully, i.e., the volume of a gas is the same as that of the container.

(iii) Gases can be compressed easily.

(iv) The kinetic energy of particles in gaseous state is maximum.

(v) Gaseous particles move randomly at high speed. They hit each other and also the wall of the container.

VAPOUR:

It is used to describe those gases that usually exist as liquid at room temperature e.g., water that exists as liquid at room temperature is called water vapour when it is in gaseous state.

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Note: The state of a matter can change into another state by changing the temperature.

SUBLIMATION:

Change of state direct from solid to gas without changing into liquid state (or vice versa) is called sublimation.

SUBLIME SUBSTANCE:

Any substance that shows the property of sublimation is known as sublime substance. Some such substances are Ammonium chloride, Iodine, Benzoic acid, Naphthalene, Camphor etc.

SUBLIMATE:

The solid formed when a sublime substance cools from its gaseous state is called sublimate.

EFFECT OFCHANGE OF PRESSURE AND TEMPERATURE ON GASES:

Applying pressure and reducing temperature can liquify gases.

EVAPORATION:

It is the phenomenon of change of a liquid into gas at any temperature below its boiling point. It is a surface phenomenon. The particles of a liquid present on the surface gain energy and leave the surface.

FACTORS AFFECTING EVAPORATION:

(i) Increase in surface area increases the rate of evaporation.

(ii) Decrease in humidity increases the rate of evaporation.

(iii) Increase in wind speed increases the rate of evaporation.

(iv) Increase of temperature increases the rate of evaporation.

Effect of evaporation:

 Evaporation causes cooling.

Fusion/Melting:

 It is the change of solid into liquid state.

Solidification:

 It is the change of liquid state to the solid state.

Boiling:

 It is a bulk phenomenon. Particles from bulk (whole) of the liquid change into vapour state.

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