Give reasons: (a) A gas can fill the whole vessel in which it is enclosed. (b) Solids cannot be compressed. (c) Liquids can flow. (d) When magnesium is burnt in air, there is an increase in mass after the reaction.
(a) Because, in gases, the molecules are free to move. They are not stuck to each other and the intermolecular force of attraction is least In the gases. So the gas almost filled the whole vessel in which it is enclosed.
(b) In solids, particles are closely packed. There Is a strong force of attraction and the intermolecular space is almost zero. Therefore the molecules are not free to move. which makes them hard and rigid. So solids can not be compressed.
(c) In liquids, intermolecular force is weaker because the particles are not closely packed and hence there is large intermolecular space. So molecules in a liquid can move randomly and hence liquids can flow easily.
(d) When magnesium ribbon is burnt in air, a white solid, magnesium oxide Is formed. The mass of magnesium oxide is more than the mass of magnesium. This is because the mass of oxygen used is not taken. If that is considered, the total mass of the reactants and the products IS found to be almost equal.