Matter

Introduction

Question 1

Explain the meaning of the the term 'matter'.

Answer

Matter is defined as anything that

• occupies space
• has mass
• can be perceived by the senses. e.g. living and non-living matter.

Question 2

Matter in any state is composed of small particles - molecules, atoms or ions.
Differentiate the terms above in italics.

Answer

Question 3

Differentiate between the two characteristics of matter - 'mass' & 'weight'.

Answer

Question 4

State which of the three states of matter i.e. solids, liquids or gases - have

(a) No definite volume

(b) A definite shape

(c) High density

(d) No free surfaces

(e) Particles which diffuse very easily.

Answer

(a) No definite volume — gases

(b) A definite shape — solids

(c) High density — solids .

(d) No free surfaces — gases

(e) Particles which diffuse very easily — gases

Kinetic molecular theory

Question 5

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 between them. i.e. inter-particle space.

(b) Inter-particle attraction — All particles attract each other with a force which is

• maximum - if the particles are close to each other &
• minimum - if the particles are at a distance from each other.

(c) Energy possessed by particles of matter — Particles are in continuous motion and hence possess energy called Kinetic Energy. Application of heat increases Kinetic Energy of particles which then move more randomly.

Question 6

State in which of the following examples i.e. 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) Inter-particle space maximum — a light gas

(b) Inter-particle attraction maximum — a piece of wood

(c) Energy possessed by particles of matter, very large — a light gas

Comparative study - solids, liquids & gases

Question 7

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 in solids is about their own position. The reason for this is that inter-particle space is minimum in solids, as a result particles are closely packed and hence movement of atoms or molecules is about their own position.

Question 8

'Inter-particle attraction between atoms of gases is very weak'. State five properties of gases which correlate as a consequence of the weak inter-particle attraction between particles of gases.

Answer

Gases have weak inter-particle attraction. They are therefore,

• least - rigid & have
• no definite - volume
• no definite - shape
• no - free surface
• rapidly - diffuse with other gas particles.

Change of state of matter - interconversion

Question 9

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

Change of state of matter from one state to another and back to its original state is called interconversion of matter. This is brought about by change in temperature, pressure.

(a) Melting — It is the conversion of a solid into a liquid on heating. e.g., ice to water

(b) Vaporisation — It is the conversion of a liquid into a gas on heating. e.g., water to water vapour.

(c) Liquefaction or condensation — It is the conversion of vapour into a liquid. e.g., water vapour to water.

(d) Solidification or freezing — It is the conversion of a liquid into a solid. e.g., water to ice.

(e) Sublimation — It is the conversion of a solid directly into a gaseous [vapour] state and on cooling directly back to solid state without changing into liquid state. e.g. naphthalene sublimes at room temperature.

Question 10

Draw a labelled schematic diagram representing the terms - (a) to (e) involved in the inter-conversion of matter.

Answer

Below labelled diagram represents the different terms involved in the inter-conversion of matter:

Change of state of matter - kinetic theory

Question 11

With reference to inter-conversion of matter - on the basis of kinetic theory - explain in brief the conversion of:

(a) A solid into a liquid

(b) A liquid into vapour [or gas]

(c) Vapour [or gas] into a liquid

(d) A liquid into a solid

With special reference to inter-particle space & inter-particle attraction at the different stages of conversion.

Answer

(a) A solid into a liquid — On heating a solid, particles gain energy, inter-particle space increases as stored potential energy increases the space, as a result inter-particle attraction decreases and at melting point particles become free. Hence, solids change into liquids.

(b) A liquid into vapour [or gas] — On heating liquids, particles gain energy, inter-particle space increases as stored potential energy increases the space, as a result inter-particle attraction decreases and at boiling point particles become free. Hence, liquids change into gases.

(c) Vapour [or gas] into a liquid — On cooling gases, temperature falls, the potential energy in the molecules is released as heat energy. Released potential energy decreases the space and inter-particle attraction increases. As a result at liquefaction point, particles slow down and gases change to liquids.

(d) A liquid into a solid — On cooling liquids, temperature falls, the potential energy in the molecules is released as heat energy. Released potential energy decreases the space and inter-particle attraction increases. As a result at solidification point, particles slow down and liquids change to solids.

Question 12

On the basis of kinetic theory explain why, ammonium chloride sublimes and goes from solid state directly into vapour state.

Answer

Ammonium chloride being a sublimable solid, has very low force of attraction between its particles. On heating, the particles overcome the inter-particle attraction. The molecules break free and escape from the surface of the solid directly into the vapour.

Law of conservation of mass

Question 13

State the 'law of conservation of mass'. State the main points of Landolt's experiment for experimental evidence of the law. State the limitations of the law.

Answer

Law of conservation of mass

Law of conservation of mass states that whenever a chemical change takes place, the total mass of the reacting substances is exactly equal to the total mass of the products, [provided masses are measured under similar conditions].

Main points of Landolt's experiment

• In an 'H' shaped tube as shown in the figure, Landolt introduced a solution of sodium chloride [NaCl] and silver nitrate [AgNO₃] in the limbs of the tube and sealed it and weighed it.
• The solutions were mixed by shaking to obtain a white precipitate of silver chloride.
• The tube was again weighed after the experiment.

Result : Weight of H tube + reactants = Weight of H tube + products.

Hence, total mass of reactants = total mass of products

Limitations of the law

• Chemical energy stored up in the reactants is released in the form of heat and light.
• Hence, mass is converted to energy and thus mass and energy are to be considered together.
• Hence, a very slight error in the experiment was observed.

Objective Type Questions

Question 1

Select the correct answer from A, B, C, D & E for each statement given below:

A: Solid

B: Vaporization

C: Ion

D: Gases

E: Heat

1. An atom or group of atoms — having a resultant charge.

2. The state of matter which has — least density & no free surfaces.

3. In Landolt's experiment — the form in which the chemical energy stored up in the reactants — is released.

4. The process of change of a liquid into vapour [gas] on heating.

5. The state of matter, where the inter-particle attraction between particles is maximum.

Answer

1. C: Ion

2. D: Gases

3. E: Heat

4. B: Vaporization

5. A: Solid

Question 2

With reference to the liquid state of matter — answer the following:

1. On heating the liquid, do the particles gain or lose energy.

2. The heat energy supplied to the liquid is absorbed by its molecule & stored as which form of energy.

3. How does the stored energy, have effect on inter-particle space.

4. State why the inter-particle attraction decreases to negligible.

5. At what point will the particles become free and escape as gas.

Answer

1. Gain energy

2. Potential energy

3. Stored potential energy increases the inter-particle space.

4. As the inter-particle space increases, the force of attraction (or inter-particle attraction) decreases to negligible.

5. At boiling point the particles become free and escape as gas.

Question 3

Complete the statements by filling the blanks with the correct word from the bracket.

1. In naphthalene, the inter-particle attraction is ............... [high/low].

2. The law of conservation of mass, is strictly valid if mass and ............... [energy/volume] are considered together.

3. When inter-particle space increases, the inter-particle attractive force ............... [decreases/increases]

4. Kinetic energy of molecules in helium is ............... [large/very large] compared to the kinetic energy of molecules in water.

5. Conversion of vapour [or gas] into a liquid is termed ............... [liquefaction/vaporization].

Answer

1. In naphthalene, the inter-particle attraction is low.

2. The law of conservation of mass, is strictly valid if mass and energy are considered together.

3. When inter-particle space increases, the inter-particle attractive force decreases.

4. Kinetic energy of molecules in helium is very large compared to the kinetic energy of molecules in water.

5. Conversion of vapour [or gas] into a liquid is termed liquefaction.

Question 4

Give reasons for the following:

1. Particles of matter possess energy called kinetic energy.

2. Solids cannot be compressed, but gases are highly compressible.

3. Kinetic energy of molecules of gases is very large & of solids, the least.

4. On heating a sublimable solid, the molecules break free & escape from surface of the solid directly into vapour.

5. Particles of matter move more rapidly on application of heat.

Answer

1. Particles of matter are in continuous motion and hence possess energy called kinetic energy.

2. As inter-particle space in solids is minimum, hence, they cannot be compressed. Gases on the other hand, have very large inter-particle space, hence are highly compressible.

3. As inter-particle space in gases is very large and inter-particle attraction is negligible, hence they are in random motion all the time and posses high kinetic energy whereas solids have minimum inter-particle space, maximum inter-particle attraction and they can move only about their own position. Hence they have least kinetic energy.

4. Sublimable solid have very low force of attraction between their particles. On heating, these solids overcome the inter-particle attraction and the molecules break free & escape from surface of the solid directly into vapour.

5. Application of heat increases the kinetic energy of the particles which then move more randomly.

Question 5

Complete the blanks with reference to interconversion of matter on basis of kinetic theory - with the word 'increases', 'decreases', 'gain', 'lose' or 'overcome' in each case.

1. During melting of solids, the inter-particle space ...............

2. During vaporization, the liquid particles ............... energy.

3. During liquefaction, the particles ............... energy.

4. During solidification, the inter-particle space ...............

5. During sublimation the inter-particle attraction is ...............

Answer

1. During melting of solids, the inter-particle space increases.

2. During vaporization, the liquid particles gain energy.

3. During liquefaction, the particles lose energy.

4. During solidification, the inter-particle space decreases.

5. During sublimation the inter-particle attraction is overcome.