[3 Mark Question Answer]

Question 13 Marks

What is inter$-$conversion of matter. Give the meaning of the terms involved in inter$-$conversion of matter $–$
$(a)$ Melting
$(b)$ Vaporisation
$(c)$ Liquefaction or condensation
$(d)$ Solidification or freezing
$(e)$ Sublimation.

Answer

$\text{INIERCON VERSION OF MATTER}$ :
“Change of state of matter from one state to another state and back to its original state is called inter$-$conversion of matter.”
$(a)\ \text{MELTING}$ : Conversion of a solid into a liquid on heating e.g. ice to water.
$(b)\ \text{VAPORISATION}$ : Conversion of a $–$ liquid into vapours $($or gas$)$ on heating e.g. water to water vapour.
$(c)\ \text{LIQUEFACTION}$ or $\text{CONDENSATION}$ : Conversion of $\text{VAPOUR} ($or gas$)$ into a $\text{LIQUID}$ on cooling e.g. water vapour to water.
$(d)\ \text{SOLIDIFICATION OR FREEZING}$ : Conversion of a $\text{LIQUID}$ into a $\text{SOLID}$ e.g. water to ice.
$(e)\ \text{SUBLIMATION}$ : Conversion of a $\text{SOLID}$ directly in $\text{GASEOUS} ($vapour$)$ state and on cooling directly back to $\text{SOLID}$ e.g. Naphthalene sublimes at room temperature.

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Question 23 Marks

In which of the three states of matter $–$ solids, liquids or gases is the movement of atoms about their own position. Give a reason for the same.

Answer

Movement of atoms[molecules] in solids are about their own position.

This is because of Minimum Inter Particle space and very strong inter$-$particle attraction among atoms.

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Question 33 Marks

State in which of the following examples Le. a piece of wood, water, a light gas is the $–$
$(a)$ Inter$-$particle space maximum
$(b)$ Inter$-$particle attraction maximum
$(c)$ Energy possessed by particles of matter, very large.

Answer

$(a)$ A light gas
$(b)$ a piece of wood
$(c)$ a light gas

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Question 43 Marks

State the main postulates of the kinetic theory with special reference to $–$
$(a)$ Inter$-$particle space
$(b)$ Inter$-$particle attraction
$(c)$ Energy possessed by particles of matter.

Answer

$(a)$ Inter$-$particle space : The particles are arranged in a way such that they have spaces existing between them. i.e. intermolecular space.
$(b)$ Inter$-$particle attraction : All particles attract each other with a force which is maximum if the particles are close to each other and minimum if the particles are at a distance from each other i.e. decreases with increase distance and vice$-$versa.
$(c)$ Energy possessed by particles of matter : Since particles are in continuous motion, they possess energy called kinetic energy. Application of heat increases kinetic energy of particles $–$ which then move more randomly.

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Question 53 Marks

Matter in any state is composed of small particles $–$ molecules, atoms or ions. Differentiate the terms above in Italics.

Answer

Molecules : A molecule is the smallest particle of a substance that can normally exist separately and retain the characteristics of the substance, e.g. $\ce{O_2, H_2, Cl_2}$ are molecules.
Atoms : An atom is the smallest particle of an element which can take part in a reaction and is considered the basic unit of matter, e.g. $\ce{O , H , Cl}$ are atoms.
Ions: An ion is any atom or a group of atoms which has a resultant charge due to loss or gain of electrons, e.g. $\ce{O ^{2-}, H ^{1+}, Cl ^{1-}}$ are ions.

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