Matter

Matter is anything that can be perceived by the senses. It occupies space, has mass and can neither be created nor destroyed.

The main physical properties of matter are:

1. Colour — Different substances can be distinguished by their varied colours.
2. Odour — Matter shows variation in odour or smell.
3. Solubility — Matter may vary in its solubility in water or other solvents.
4. Melting and boiling points — Substances show variation in their melting and boiling points.

(a) Solids occupy space

Procedure — Take a measuring cylinder and fill it to the 100 cc mark with water. A solid is slowly immersed inside the cylinder.

Observation — The water level rises above the 100 cc mark and if the solid is removed, the water level comes back to the 100 cc mark.

Conclusion — The solid occupies space and displaces some water, causing the water level to rise. Therefore, all solids occupy space.

(b) Solids have mass

Procedure — On one side of the scale, a solid is placed.

Observation — The scale tilts to the side where the solid is placed.

Conclusion — Therefore, all solids have mass.

(c) Solids have a definite volume

Procedure — A solid is taken and placed in containers of different shapes.

Observation — The solid retains the same volume irrespective of the shape of the container.

Conclusion — Therefore, all solids have a definite volume.

(a) Liquids have mass

Procedure — On one side of the scale, a liquid in a beaker is placed.

Observation — The scale tilts to the side where the liquid is placed.

Conclusion — The mass of the liquid in the beaker causes the scale to tilt. Therefore, all liquids have mass.

(b) Liquids have a definite volume

Procedure — Liquid in a measuring cylinder is poured into another container.

Observation — The volume of the liquid in the container is the same as that in the measuring cylinder.

Conclusion — Liquids retain their own volume in any shaped container. Therefore, all liquids have a definite volume.

(c) Liquids have no definite shape

Procedure — Liquid in a measuring cylinder is poured into different containers.

Observation — The liquid takes the shape of each container.

Conclusion — Therefore, liquids have no definite shape.

(a) Gases occupy space

Procedure — An empty glass tumbler is lowered into a beaker of water.

Observation — On tilting the tumbler to one side, bubbles of air are seen coming out from the lower end of the tumbler.

Conclusion — The air inside the tumbler is displaced and bubbles are pushed out. Therefore, all gases occupy space.

(b) Gases have mass

Procedure — A balloon is inflated with air and placed on one side of the scale.

Observation — The scale tilts to the side where the balloon is placed.

Conclusion — The mass of the gas i.e. air in the balloon causes the scale to tilt. Therefore, all gases have mass.

(c) Gases have no definite volume or shape

Procedure — A gas jar filled with a coloured gas, e.g. brown nitrogen dioxide, is inverted over an empty beaker.

Observation — The coloured gas empties out from the gas jar and completely takes up the volume and shape of the beaker.

Conclusion — Therefore, gases have no definite volume or shape.

Interconversion of matter involves the change of state of matter from one state to another state and back to its original state. The change is brought about by changes in temperature and pressure.

The change of state of matter with reference to ice, water and water vapour is shown below:

• Ice (solid) changes to water (liquid) on heating — Melting
• Water (liquid) changes to water vapour (gas) on heating — Vaporization
• Water vapour (gas) changes back to water (liquid) on cooling — Condensation
• Water (liquid) changes back to ice (solid) on cooling — Freezing

(a) Melting — The process of conversion of a solid into a liquid on heating. (e.g. ice to water)

(b) Vaporization — The process of conversion of a liquid into a vapour on heating. (e.g. water to water vapour)

(c) Condensation — The process of conversion of a vapour (or gas) into a liquid(e.g. water vapour to water)

(d) Freezing — The process of conversion of a liquid into a solid(e.g. water to ice)

(e) Melting point — The constant temperature at which a solid melts into a liquid(m.p. of ice = 0°C)

(f) Boiling point — The constant temperature at which a liquid starts boiling. (b.p. of water = 100°C)

Observation — The sugar or the sand goes into the space between the pebbles and the glass balls respectively.

Conclusion — This imaginative demonstration shows that there are intermolecular spaces between particles and that smaller particles can occupy these spaces.

Experiment (Ball and ring apparatus)

Procedure — A simple ball and ring apparatus is taken, which consists of a metal ball which can just pass through the circular metal ring. The metal ball is then heated for a certain period of time.

Observation — After heating, the metal ball does not pass through the ring because it has expanded in size on heating.

Conclusion — All solids expand on heating.

(a) In solids, the particles have minimum intermolecular space and a very strong force of attraction between them. They are closely packed and can only vibrate about their fixed positions. Hence, solids have a definite shape and are highly rigid. In gases, the particles have maximum intermolecular space and a very weak force of attraction between them, so they move freely in random directions. Hence, gases have no definite shape and are the least rigid.

(b) Sugar dissolves in water (it is soluble), while talcum powder does not dissolve in water (it is insoluble). On the basis of this difference in solubility, sugar can be distinguished from talcum powder using water.

(c) Freezing is the process of conversion of a liquid into a solid. When water is cooled below 0°C, it loses heat and changes into the solid state. Hence, water on freezing turns into ice.

(d) When a bottle of perfume is opened, the perfume evaporates and its vapour particles diffuse rapidly through the air. Since diffusion is very fast in gases, the odour spreads and can be sensed over a long distance.

(a) Solids and liquids have a definite volume but gases do not.

(b) The space between atoms in gases is maximum while in solids is minimum.

(c) Conversion of a vapour into a liquid is called condensation.

(d) Sugar is an example of a crystalline substance.

(a) False
Correct Statement — Solids are not compressible (incompressible) but are highly rigid.

(b) False
Correct Statement — Atoms/molecules in gases move continuously in random directions. It is the atoms/molecules in solids that vibrate about their fixed positions.

(c) True

(i) From the three states of matter, solids expand the least.

(ii) Brownian movement is maximum in gases.

(iii) Cohesive forces are negligible in gases.

(iv) Matter can change from one state to another by change in temperature or pressure.

(v) The space between atoms [molecules] of solids is minimum.

(vi) Intermingling of molecules is called diffusion.

(vii) Ice on absorption of heat converts to 'X' by a process called melting. 'X' changes to water vapour on heating. Water vapour changes back to 'X' on condensation. The constant temperature at which ice changes into 'X' is called its melting point.

The following are physical properties of a substance:

(i) Chlorine gas has a strong irritating odour. — (odour)

(ii) Sodium nitrate is soluble in water, but calcium carbonate is not. — (solubility)

(iv) Manganese dioxide is black in colour. — (colour)

(v) The melting point of ice is 0°C. — (melting point)

(vii) Water acidified with dilute sulphuric acid is a good conductor of electricity. — (electrical conductivity)

(viii) Naphthalene on heating directly turns into vapour. — (change of state / sublimation)

(ix) Hydrogen sulphide gas has a strong rotten egg odour. — (odour)

(x) Sulphur is a yellow amorphous powder, insoluble in water. — (colour and solubility)

Explanation

Statements (iii) and (vi) are chemical properties as they involve chemical reactions.