Give reason: Solids can not be compressed.

Solids are made up of tiny particles which are tightly packed due to the greater force of attraction between the particles. Thus, solids attain a definite shape and can not be compressed easily.

Give reason: Liquids can flow.

The particles in liquids have a lot of inter-particle space and possess greater kinetic energy. The particles thus tend to move freely in the given volume. Liquids have no definite shape but definite volume.

Give reason: When magnesium is burnt in the air, there is an increase in mass after the reaction.

When magnesium is burnt in the air, the oxygen from the air reacts with magnesium to form a product magnesium oxide. Thus, the mass of utilised oxygen also gets added to the mass of magnesium used for burning. The reaction is as follows: 2 Mg + O 2 → 2 MgO

Give two examples for the following: The substances which sublime.

Sublimation is the process in which solid turns directly into gas without converting into liquid. The substances undergoing sublimation are termed as sublimates. Solid → heat Gas Two examples of sublime substances are ammonium chloride and dry ice.