Matter and Its Composition

Introduction

Question 1

Explain the meaning of the term matter with special reference to the term 'substance'.

Answer

Matter is the basic substance of which all materials, living or non-living, are made up of. It occupies space, has mass, can be perceived by the senses and can be neither created nor destroyed.

Question 2

Name the three states of matter. On what basis are the three states of matter classified?

Answer

The three states of matter are Solid, Liquid, & Gas. The three states of matter are classified on the basis of intermolecular spaces between their particles which is least in solids, more in liquids and maximum in gases.

Experimental Study

Question 3

Each of the three states of matter has mass. Explain with the help of simple experiments that each state of matter has mass.

Answer

Solids

Procedure — A solid placed on the scale, causes the scale to tilt towards one side.
Conclusion — The scale tilts due to the mass of the solid, hence all solids have mass.

Liquids

Procedure — A liquid placed on the scale, causes the scale to tilt towards one side.
Conclusion — The scale tilts due to mass of the liquid, hence all liquids have mass.

Gases

Procedure — A balloon placed on the scale, causes the scale to tilt towards one side.
Conclusion — The scale tilts due to mass of the gas, hence all gases have mass.

Question 4

A measuring cylinder is filled with water to a particular mark. A piece of solid is immersed inside the measuring cylinder. State why the level of the water in the measuring cylinder will rise up. If the solid is removed, what will be the new level of the water in the measuring cylinder. Give a reason for your answer.

Answer

As all solids occupy space and stone occupies the space of the water hence pushes the water level up.

On removal of the stone, the water level falls back to its original level. The reason is that all solids occupy space, when the stone is removed, the space is empty and water takes that place and drops to its original level.

Question 5

A glass beaker is half filled with water and an empty glass tumbler is inverted and lowered inside the glass beaker. State your observations on tilting the tumbler below the level of the water in the glass beaker. Give a reason for your answer.

Answer

An empty glass tumbler when lowered inside a glass beaker half-filled with water and tilted, the air inside the tumbler is displaced and bubbles of air are seen coming out. The reason is that the air is pushed out by water on tilting the tumbler inside the beaker of water since air or gases occupy space.

Question 6

Differentiate the general properties of solids, liquids, and gases in the form of a table with reference to-

(a) Mass

(b) space

(c) Volume

(d) shape

(e) compressibility

(f) density

(g) free surfaces

(h) diffusion

Answer

Question 7

State in which of the three states of matter

(a) are the atoms or particles far apart

(b) the space between the particles is minimum

(c) the force of attraction between the particles is very weak

(d) the movement of particles are neither about their own positions nor in random direction

Answer

(a) Gases

(b) Solids

(c) Gases

(d) Liquids

Question 8

Give a reason why-

(a) Solids have a definite volume and a definite shape

(b) Liquids have a definite volume but no definite shape

(c) Gases have no definite volume and no definite shape.

Answer

(a) Solids have negligible intermolecular space as the molecules are closely packed and the force of attraction is maximum. This arrangement of molecules gives them a definite volume and a definite shape.

(b) In liquids the molecules are less tightly packed as compared to solids, so the intermolecular space is larger and force of attraction is weaker. This gives them a definite volume but no definite shape.

(c) In gases the molecules are far apart so the intermolecular space is very large and the force of attraction is the least. Hence, gases have no definite volume and no definite shape.

Question 9

Particles of matter possess energy due to their random motion. Compare the particles in a solid, liquid, & in a gas with reference to the amount of kinetic energy possessed by each.

Answer

Solids — As particles in solids move about their mean positions only, hence they posses the least kinetic energy.

Liquids — As particles in liquids are free to move within the liquid, hence they posses large kinetic energy.

Gases — As particles in gases can move freely in any direction, hence they posses very large or maximum kinetic energy.

Question 10

Describe simple experiments to show that —

(a) Particles of matter have intermolecular attraction.

(b) Particles of matter are closely packed in solids and less in liquids.

Answer

(a) Simple experiment to show that particles of matter have intermolecular attraction:

Procedure : Globules of mercury are placed in a petri dish and kept at a distance. Then the petri dish is shaken, and the mercury globules come together forming a big globule.

Conclusion : The above activity concludes that a force of attraction exists between the particles of matter.

(b) Simple experiment to show that particles of matter are closely packed in solids and less in liquids:

Procedure : 100 ml of water is taken in a measuring cylinder. Crystals of sugar (solid) are added to the water to obtain sugar solution. The volume of water, even after adding sugar remains the same at 100 ml.

Conclusion : This concludes that particles of matter are closely packed in solids and less closely packed in liquids. The sugar particles fill the intermolecular spaces which must be existing between the water molecules and hence the level of the water in the measuring cylinder does not rise.

Question 11

A crystal of iodine is placed in a closed flat bottom flask & heated. State how you would conclude from the observations seen, that interparticle space is minimum in solids & maximum in gases.

Answer

A crystal of iodine is heated in a closed flat bottom flask. The crystal containing 'X' no. of particles turns into vapours, which also contain 'X' no. of particles and fills the complete flask.
Hence, we can conclude that particles of solid are more closely packed, whereas, particles of gas are least closely packed and fill the flask completely.

Question 12

Explain the term 'interconversion of matter' - with ice as a starting material. State the term which refers to the conversion of a substance on heating from -

(a) Solid state to liquid state.

(b) liquid state to vapour state.

(c) vapour state to liquid state.

(d) liquid state to solid state.

Answer

Taking ice as a starting material, 'interconversion of matter' can be understood in the following way:

1. On heating, ice which is in solid state melts and changes into water which is in liquid state.
2. On further heating, water changes into vapour which is in gaseous state.
3. When water vapour is allowed to cool, it changes from gaseous state to liquid state forming water.
4. On cooling water further, it changes to solid state forming ice.

Thus, 'interconversion of matter' involves change of state of matter from one state to another and back to its original state by change in temperature or pressure.

(a) Melting

(b) Vaporisation

(c) Liquefaction or Condensation

(d) Solidification or freezing

Question 13

Give a reason why solids and liquids co-exist at their melting points.

Answer

At melting point, solid start changing into liquid state. Heat is absorbed and it is used in change of state without any rise in temperature till all the solid has changed into liquid state. Hence, the two states i.e., solid and liquid co-exist at melting point.

Objective Type Questions

Question 1

Match the characteristics of the three states of matter in List I with their correct answer from List II

Answer

Question 2

Select the correct answer from the choice in bracket to complete each sentence:

1. Matter is defined as anything that occupies ............... & has ............... [mass/volume/space].

2. The three states of matter are classified on the basis of differences of certain ............... [chemical/physical] properties.

3. Matter made up of one kind of particles is said to be ............... [heterogeneous/homogeneous]

4. Particles in a gas possess ............... [least/very large] kinetic energy.

5. The intermolecular force of attraction is ............... [negligible/maximum] in solids.

Answer

1. Matter is defined as anything that occupies space & has mass.

2. The three states of matter are classified on the basis of differences of certain physical properties.

3. Matter made up of one kind of particles is said to be homogeneous.

4. Particles in a gas possess very large kinetic energy.

5. The intermolecular force of attraction is maximum in solids.

Question 3

Give reasons for the following:

1. Solids have a definite shape or Volume.

2. Liquids have one free upper surface only.

3. Globules of mercury kept in a petri dish, which is shaken slowly, come together forming a big globule.

4. A crystal of Iodine on slow heating in a closed flask, turns into vapours & fills the complete flask.

5. An empty tumbler lowered into a glass beaker containing water, on tilting shows bubbles of air coming out, but when not tilted, no bubbles are seen.

Answer

1. Solids have negligible intermolecular space as the molecules are closely packed and the force of attraction is maximum. This arrangement of molecules gives them a definite volume and a definite shape.

2. Due to large intermolecular spaces and weaker intermolecular force of attraction, liquids have a definite volume but no definite shape. As a result, a liquid takes the shape of the container in which it is kept. So the top surface of the container is the only free upper surface it has.

3. The intermolecular force of attraction between the particles of mercury causes the globules of mercury to come together and form a big globule when the petri dish is shaken slowly.

4. Particles of iodine when heated turn into vapours, which is in gaseous state. Particles of gas are least closely packed and fill the flask.

5. The empty tumbler contains air inside it. When it is lowered into the glass beaker and tilted, water enters the tumbler and pushes out the air inside it which is seen escaping in the form of air bubbles coming out of water. When the tumbler is not tilted, water cannot enter the tumbler so the air inside it is not displaced and no bubbles are seen.

Question 4

State the correct term from A, B, C, D, E or F in List II which represents the -change of state of matter or its relevant property from List I

Answer

Question 5

Match the arrangement of atoms in three states of matter in List I with the correct state in List II

Answer