# Study Portal 13 – Chapter 13

Physical State of Matter

Q.1.     Fill in the blanks with appropriate words.

1. i) Matter in the universe exists in Four
2. ii) 1 atmosphere pressure is equal to 760

iii)           The volume of gas is directly related with temperature.

1. iv) The liquids have definite volume and variable
2. v) The relation between the density and the temperature is inversely proportional.
3. vi) Mixing of gas molecules is called

vii)    Boyel’s Law states that volume of a gas is inversely related to the pressure.

viii)   Solids state of matter has highest density, as compared to liquid and gas states.

1. ix) In Kelvin scale of temperature 3000C is equal to
2. x) Some elements with different shapes are called

1. i) The form of matter which does not have definite shape and volume is called:

(a) liquid    (b) gas             (c) solid           (d) plasma

1. ii) Gases can be liquefied by:

(a) Simple physical methods

(b) simple chemical methods

(c) by using physical and chemical

(d) no physical and chemical method can be used

iii)     Monometer is used for the determination of:

(a) pressure          (b) volume       (c) length         (d) area

1. iv) The vapor pressure can be determined by using:

(a) monometer                               (b) barometer

(c) both manometer and barometer

(d) neither manometer nor barometer

1. v) The different forms of an element are called:

(c) molecules                     (d) allotropes

Q3.      Answer the following questions in short.

1. i) If you take equal volumes of N2 and CO2 indifferent containers which sample will expect to have more density?

Ans.  The density is defined as the mass per unit volume of substance d=m / v, because volumes is equal and atomic mass of N2 = 2(23) = 46 and atomic mass of CO2=12+2(16) = 44 so the density of N2 is more than CO2.

1. ii) Compare different states of matter.

Ans.  The matter exists in four different states. Generally we deal with three states of matter.

1. a) Solids:- Solids are the state of matter having definite volume and definite shape.
2. b) Liquids:- Liquids are the state of matter having definite volume but indefinite shape.
3. c) Gases:- Gas is the state of matter having neither definite shape nor definite volume.

iii)     Why we can’t see most of the gases? Name 3 gases which are visible for us.

Ans.  Usually the gases are color less and so they are invisible, but some gases have colour too and they are Cl2, NO2 and O3.

1. iv) Compare diffusion and effusion process in gases.

Ans.  Diffusion is defined as spontaneous mixing up of molecules by random motion and collision to form a homogeneous mixture and Effusion is escaping of gas molecules through a tiny hole into a space with lesser pressure.

1. v) Explain the term pressure of gases, also describe its unit?

Ans.  Pressure (P) is defined as the force (F) exerted per unit

surface area (A), P = F / A. The SI unit of force is Newton and that of area is m2 so Nm-2. It is also called Pascal (Pa).

1. vi) Why we use Kelvin scale in solving gas Laws Problem?

Ans.  The Kelvin scale of temperature is denoted by the symbol ‘K’ and note that no degree sign is used in this scale 0 K= -2730C. The Kelvin scale is needed for calculations specially, because in this scale the temperature can not be in negative values or even zero.

vii)    Can you explain why wet skin under the fan feels cool?

Ans.  Evaporation is a cooling process. Wet skin under the fan the high kinetic energy molecules vaporize the temperature of remaining molecules falls down. To compensate this deficiency of energy the molecules of liquid (wet skin) absorb energy from the surroundings. As a result the temperature decrease and we feels cool.

viii)   Differentiate between rates of diffusion among gases and liquids with examples?

Ans.  Diffusion in gases is defined as the mixing of gas molecules into each other e.g. when a perfume is sprayed in a room, it readily spreads across the room. The diffusion in liquid just like of gases mixing of molecules with one another. The diffusion is easily observed in a glass of water when a drop of ink is placed in it.

1. ix) Why solids have higher melting points than liquids.

Ans.  The molecules in the solid lie close to each other and thus they have high values of intermolecular attractions, therefore it becomes hard to separate them as compared to the liquids. Thus they have high and sharp melting points.

1. x) According to their shape what types of solids are found in nature?

Ans.  According to their general appearance solids can be classified into two types; amorphous solids and crystalline solids.

Q4.      Answer the following question with reasoning.

1. i) Why pressure of a gas scaled in a container when temperature is increased?

Ans.  Pressure is defined as the force per unit area. Like liquids and solids gases also exert pressure, and you may have noticed this pressure many times in your life e.g. while comparing the mass of an empty and filled home gas cylinder and you may have also noticed this pressure while filling air tyres and tubes using pump. Gas molecules are always in continuous state of motion. Molecules strike with the wall of the container. When temperature is increased the motion of molecules are also increased in result the pressure of gas increased.

1. ii) Explain in light of KMT what would happen with respect pressure when more quantity of a gas is added to container of gas?

Ans.  A gas consists of extremely small particles known as molecule or atoms which are dispersed through out the container. The actual volume of the molecules is neglected able compared to the total volume of the container gas. The distance between the molecules are very large thus the gas molecules can move freely independent of each other. There are no any attractive forces among the gas molecules. The pressure of gas is caused by the hits recorded by molecules on the walls of the container. When more quantity of a gas is added to container, the pressure of gas increased.

iii)     Arrange the gases Cl2, H2, NH3 in order of increasing speed of their molecules at 250C.

Ans.  Molecules of a gas move haphazardly, collide among themselves and with the walls of the vessel. So the molecules have certain velocities. All the molecules of a gas do not have the same velocities at a given temperature. Because the molar mass of H2 is 16 times less than that of O2, so the velocities for H2 will be four times higher that of O2 at 250C. So arrangement of Cl2, H2 and NH3 are H2, NH3 and Cl2.

1. iv) What would you expect to happen in respect of volume when a balloon filled with air is placed in the freezer of a refrigerator?

Ans.  French scientist J.Charles in 1787 presented his law that states “the volume of a given mass of gas is directly proportional to the absolute temperature if the pressure is kept constant “Mathematically it is represented as

Volume       Temperature    V    T

V         =          KT        where K is proportionality constant.

So when a balloon filled with air is placed in the freezer of a refrigerator. It squeezed / shrivel due to the cooling of freezer.

1. v) Name three methods by which the volume of a gas can be decreased.

Ans.  First Method:- According to Boyles Law “volume of a given mass of a gas is inversely proportional to its pressure provided the temperature remains constant, so for decrease of volume pressure will be increase.

Second Method:- According the Charles Law “the volume of a given mass of a gas is directly proportional to the absolute temperature if the pressure is kept constant”. So for decrease of volume temperature will be decrease.

Third Method:- According to Jaul-Thomson effect, when highly compressed gas is allowed to expand its temperature decrease. So when temperature increases the volume decreases.

Q.5.  How can you differentiate between the various forms of matter?

Ans.     Differentiation between the various forms of matter.

 No. GASES LIQUIDS SOLIDS 1.           2.     3.     4.   5.     6.     7.     8. It is the form of matter which have neither definite shape nor definite volume. Molecules lie for apart from each other. Molecules are free to move.   K.E of molecules is highest. Intermolecular forces are very weak. Molecular arrangement is irregular. Molecules can be compressed easily. Rate of diffusion is very high. It is the form of matter which does not have definite shape but has definite volume.   Molecules lie little close to each other.   Molecules can move in a limited way. K.E is intermediate Intermolecular forces are fairly stronger. Molecular arrangement is some what regular. Molecules can be compressed up to a few degrees. Rate of diffusion is lower than gases. It is the form of matter which has both definite shape and definite volume.     Molecules are very close to each other.   Molecules have only oscillatory movement at their own place. K.E is lowest. Intermolecular forces are very strong. Molecules are highly arranged.   Molecules can not be compressed.   No diffusion.

Q6.   Derive a relation to show that volume and pressure have indirect relation?

Ans.  In 1662 Robert Boyle studied the relation between volume and pressure of a gas at a constant temperature.

According to this Law “The volume of given mass of a gas is inversely proportional to the pressure at constant temperature” i.e.

V                    1 / p     (T= constant)

V            =          constant x 1 / p

PV          =          Constant

P1V1        =          constant           in the same way

P2V2        =          constant           so

P1V1        =          P2V2

Where P1, V1 are initiated pressure and volume while P2, V2 are final pressure and volume. If a graph is plotted between pressure and volume a curve is obtained indicating that volume decreases with the increase in pressure.

Q7.      Discuss the importance of Charles’ Law?

Ans.  In 1787 Jacques Charles told that volume of a given mass of a gas is directly proportional to the temperature at constant pressure. Mathematically it is represented as

V                    T          (At constant pressure)

V            =          constant ´ T

V / T                   =          constant

V1 / T1     =          V2 / T2

Where V1, T1 are initial values and V2, T2 are final values of volume and temperature. While plotting a graph between ‘T’ and ‘V’ a straight line is obtained and when this line is increased downwards it touches zero volume line at -273.150C which means that volume at this point is zero. This is not possible so this temperature is not achievable. From here we start a new scale in which zero or negative values are not possible. This new scale is called Kelvin scale.

Q8.   Define the term Allotropy? How the allotropy of oxygen effect our life?

Ans.  The word allotropy has been derived from two parts where allos stands for other and tropy (from tropos) mean forms. Thus allotropy means other forms.

The allotropic forms are the different forms of an element, which have although the same chemical properties but different structure for example oxygen has two allotropic forms.

Oxygen   O2 – Colorless (oxygen)

Oxygen   O3 – Blue (ozone)

Oxygen is essential for life, plants and animals can not live without it.

Ozone is molecule consists of three oxygen atoms joined together by covalent bond. Ozone is much more reactive than ordinary oxygen. It spontaneously reverts back to diatomic oxygen releasing extra atom of oxygen.

Q.9.  What are the various types of solids? Give daily life examples to differentiate?

Ans.  According to their general appearance solids can be classified into two types; Amorphous Solids and Crystalline Solids.

Amorphous Solids:- Amorphous means shapeless solids in which the particles are not regularly arranged or their regular shapes are destroyed are called amorphous solids, e.g. plastics, rubber and glass.

Crystalline Solids:-  Solids in which particles are arranged in a definite three-dimensional pattern are called crystalline solids. They have definite surfaces or feces. Each face has definite angle with the other. They have sharp melting points. Examples of crystalline solids are diamond, sodium chloride etc.

Q.10.   An ideal gas is kept in a cylinder of moveable piston of mass 1kg, has a volume of 500 CC at the temperature of 250 C. if the temperature rises to 400 C what will be the new volume of the gas?

Ans.     Data:-

V1           =          500cc

T1            =          250C    =25 + 273        =298k

T2            =          400C    =40 + 273        =313k

V2           =          ?

By putting these values in Charle’s Law, we get

V1 / T1  = V2 / T2

V2           = V1 x T2 / T1

V2           = 500 x 313 / 298

V2           = 525.167 CC  or         525.17 CC

Q.11.   Suppose a gas is kept in a cylinder of volume 3 liters and a pressure of 2 atmospheres, if the gas is shifted into a new cylinder of volume 5 liters what will be the new pressure if the temperature remains constant.

Ans.     The given Data of the Questions.

P1 = 2 atm

V1 = 3 liters

V2 =  5 liters

P2 = ?

By putting the values in boyle’s law equation

P1V1 = P2V2 (Temperature = Constant)

P2 = P1 ´ V1 / V2

P2 = 2 ´ 3 / 5 = 6 / 5 = 1.2 atm

Q.12.   Compare the physical states of the matter with regard to intermolecular forces present between them:

Ans.  As you know that matter exists in three physical states; gas , liquids and solid . in the gaseous stats the molecules are far apart from each other . there fore intermolecular forces are vary weak in them but in the liquid and solid states intermolecular forces play a very important role on their properties in the liquid states molecule are much closer to each other as compared to gases as shown in figure.

As a result liquid molecules develop stronger intermolecular forces which effect their physical properties like diffusion, evaporation and boiling points . The intermolecular forces become so dominant in sold stats that the molecules look motionless they arrange in a regular pattern therefore they are than molecules of liquids.

Q13. Differentiates between the amorphous and crystalline solid with examples?

Ans.  The word amorphous has its origins from two parts where ‘A’ stands for without and morph from shape, thus amorphous means without shapes e.g. glass some plastics, wax and gem stones. The crystalline solids have a characteristic geometrical shape the crystalline solids are actually the true solids e.g. diamond, sodium chloride etc.

Q.14.   Compare the different physical states of the matter with regards to their typical characteristics?

Ans.  In gases the molecules are for apart from each other due to weak intermolecular forces .The gas molecules spread in all available space usually the gasses are colorless and so they are in available, kinetic energy if the molecules is highest.

In solids from of the matter having a definite shapes and volume, particles lie very close to each other and have very high intermolecular forces. Molecules move just vibratory, kinetic energy is least.

In liquids states no definite shape but have definite volume , the molecules are loosely held have limited movement in a definite region , The molecules have lesser kinetic energy the liquids have stronger intermolecular forces than the gases stats , hence they have comparatively higher melting and boiling points .

Example 5.1:- Volume of a gas at standard pressure is 4.7 liters, what will be the volume of gas when the pressure is increased to 2 atmospheres while the temperature remains unchanged.

This problem can solved using Boyel’s law equation i.e. P1V1

= P2V2 (Temp = Constant)

Here        P1         = Standard Pressure = 1 atm

V1        = 4.7 Liters

P2         = 2 atm

V2        = ?

As P1V1   = P2V2

So V2      = P1V1/P2

By putting values

V2        = 1 x 4.7/2 = 2.35 liters

Example 5.2 :- The Volume of a gas at 50 C and standard pressure is 500 ml, if the temperature drops to 0 C at same pressure what will be the new volume?

Using charle’s law equation this problems can be solved easily.

V1 / T1                 = V2 / T2 (Pressure = Constant)

And V2    = V1 x T2 /T1

The Given Data is

V1           = 500 ml

T1            =  50 C = 50+273 = 323 K

T2            = 0 C = 0 + 273 = 273 K

By putting values

V2               = 500 x 273/323 = 422.60 ml

Activity 5.1

Normal human temperature is 37 C express this Temperature to Kelvin scale just 273 is added so K = C + 273

K = 37 + 273

K = 310 K