CHEMISTRY [2 Mark Question Answer]

Ice on the absorption of heat converts to ‘X’ 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 fusion point.

On heating, candle wax melts, then turns into vapour which reacts with air to produce two new substances, carbondioxide and water. Therefore a candle on burning becomes smaller and smaller and the part of wax which has undergone chemical change cannot be recovered.

Water from oceans, rivers, lakes from leaves of trees (transpiration) changes into vapours when temperature increases or evaporates and enters the atomsphere as clouds when temperature falls the vapours change into water and some of it in the form of snow fall on mountains and earth in the form of water and hales and this continues. Thus water cycle is example of interconvertion of states of water.

As a liquid is heated, its particles starts gaining energy and move more vigorously which increases the gaps between the particles and decreasing the force of attraction. Ultimately a liquid changes into gaseous state.

During interconversion of state of matter composition of substance remains the same matter changes from one state to another and back to the original state, while chemical reaction involves re-arrangement of the molecular structure and composition changes.

The molecules of liquids and gases are far apart i.e. have more gaps, intermolecular attraction force is very less as compared to solids, hence liquids and gases can flow but solids do not as gaps in solid molecules is less and molecular force of attraction very strong

The two main types of matter are :

1. Living matter: The earth is home to all kinds of plants and animals. They can grow, move and reproduce on their own. Examples : Plant, lotus, animals, human etc.
2. Non-living matter : Most of the matter in the universe is non-living. It means that it does not grow, move or reproduce on its own. It can be natural or man made.

Matter can change from solid to liquid to a gaseous state and back to solid-state. This is called a change of state of matter.
Boiling point — The constant temperature at which a liquid starts boiling.
B.P. of water – 100°C.

Matter can change from solid to liquid to the gaseous state and back to solid-state. This is called a change of state of matter.
Melting point — The constant temperature at which a solid melts into a liquid.
M.P. of ice – 0°C.

Matter can change from solid to liquid to the gaseous state and back to solid-state. This is called a change of state of matter.
Freezing — The process of conversion of a liquid into a solid.
e.g. Water to ice.

Matter can change from solid to liquid to the gaseous state and back to solid-state. This is called a change of state of matter.
Condensation — The process of conversion of vapour into a liquid.
e.g. Water vapour to water.

Matter can change from solid to liquid to the gaseous state and back to solid-state. This is called a change of state of matter.
Vaporization — The process of conversion of a liquid into vapour on heating.
e.g. Water to water vapour.

Matter can change from solid to liquid to the gaseous state and back to solid-state. This is called a change of state of matter.
Melting — The process of conversion of a solid into liquid on heating.
e.g. Ice to water.

Physical Properties of Matter are:
Colour: All matter a be distinguished by their varied- colours.
Odour: Matter shows a variation in odour or smell.
Solubility: Matter may vary in solubility in water or other solvents.
Melting & Boiling Points: Substances variation in their melting and boiling points.

Physical Properties— They are those properties which include state, colour, odour, density etc.
Chemical Properties— They are properties which include reactions of different materials with different chemicals.

Solids have very closely packed atoms with minimum spaces between them while gases have atoms which are for apart with maximum spaces between them. Solids have a definite shape and are highly rigid while gases have no definite shape and are least rigid.