Study Portal 5 – Chapter 5

Physical States

of Matter


Q1.      Define matter and different states of matter.

Ans.    Everything which has a mass and occupies space is called matter. The universe is made up of two entitles, matter and energy. Matter exists in four different states i.e. gas, liquid, solids and plasma. The plasma state is actually a mixture of gaseous state and ions.

Q2.      Write inter conversion of three state matters.

Ans.    When we heat a solid the kinetic energy of its particles increases and they start vibrating at a higher frequency. At a particular temperature the vibrations of the particles becomes so fast that they leave their fixed position as a solid and get converted into liquid. Similarly, when a liquid is heated, its particles start moving at a very high speed and the forces of attraction between them become very week at a particular temperature. The particles of a liquid start moving so fast that they become independent of one another. At this stage, the liquid is converted into gas.

Q3.      Explain gaseous state of matters and its properties.

Ans.    A substance which has no definite shape and volume is called gas.


  • The forces of attraction between the molecules of a gas are negligible. The molecules can move freely in all direction, so a gas has no fixed shape and fixed volume. A gas takes the shape of container.
  • The molecules of a gas collide with one another and also with the walls of container. Their collision is elastic. The collision during which total energy and total momentum of colliding molecules remains same before and after collision is called elastic collision.
  • Due to collision, the molecules exert pressure on the walls of container.
  • Kinetic energy of molecules of a gas is greater than solid and liquid particles.
  • The distance between the molecules of a gas is very large as compared to the distance between the particles of a solid or a liquid. Due to this large distance a gas can be compared easily than solids and liquids.

Q4.      Compare diffusion and effusion of gases.

Ans.    Diffusion

  • Diffusion is the spontaneous mixing of molecules of different gasses by random motion and collision to form a homogeneous mixture.
  • Diffusion can also be defined as the spontaneous flow of molecules from a region of higher concentration to a region of lower concentration.

The process of diffusion is more rapid in gasses when two gasses, nitrogen dioxide and oxygen separated by a partition are allowed to mix by removing the partition, and they diffuse into each other. NO2 is brown colored gas, while O2 is colorless, after mixing the mixture gives a uniform color. Diffusion is dependent upon the temperature.


  • The passage or escape of gas molecules open by one without collision through a pin hole from their container into an evacuated space is called effusion.
  • The escape of gas molecules through a very small hole of molecules diversions into vacuum without collision is called effusion.

The escaping of molecules is not because of collision instead, they have a tendency to escape one by one. Infect the molecules of the gas are constantly colliding with the walls of vessel. When they reach the wall and find a hole in it then they pass through the hole.

Q5.      Define Pressure.

Ans.    Pressure is the force exerted by a gas per unit area. Gases exert pressure uniform in all directions. It is due to the collision of gas molecule with the wall of the container. A standard pressure of one atmosphere is the pressured exerted by exactly 76cm or 760 mm of mercury column at 00C. The SI unit of pressure is Pascal.

Q6.      Define Density.

Ans.    Mass per unit volume of a substance is called density.

Density  =           mass / volume = m / v

Unit’s density is different for gas compared to liquid and solids. Density of a gas is expressed in gm dm3.

Q7.      Define and explain Boyle’s Law.

Ans.    In 1660, an Irish chemist Robert Boyle (1627-1691) studied the effects of pressure on the volume of a given mass of air.

The volume, ‘V’ of a given mass of a air is inversely proportional to its pressure ‘P’ if the temperature ‘T’ is held constant is called Boyle’s Law.

V µ 1 / P

V = constant ´ 1 / P

PV = constant.

This relationship is known as Boyle’s Law. If the initial pressure and volume of a given quantity of gas are P1, and V1 and the pressure is changed to P2 the new volume ‘V2’ is given by the following relationship.

P1V1 = P2V2.

The grap between pressure and volume at constant temperature is called isotherm.

Q8.      Explain Charl’s Law.

Ans.    The volume of a given mass of a gas is directly proportional to the temperature measured on Kelvin scale when the pressure is kept constant.

V  T

V = constant ´ T

V / T = constant

V1 / T1 = V2 / T2 where T is the temperature on the Kelvin scale.

The Liquid State

A substance which has definite volume but no definite shape is called liquid e.g. H2O, C2H5OH.


  • Cohesive forces are also present among the particles of a liquid due to presence of these forces a liquid has a fixed volume and it keeps its level as well.
  • Distance between the particles of a liquid is very small but they can move with greater speed in all possible directions.
  • Particles of a liquid show all three types of motion on vibrational, rotational and translational.
  • The particles of liquids have no fixed positions so liquid have no fixed shapes. They attain the shape of container in which these are contained.

Q9.      Describe typical properties of liquid.

Following are the typical properties of liquids.

  • Evaporation: – The process of escape of molecules spontaneously from the surface of a liquid is called evaporation.
  • Vapor pressure: – The pressure exerted by the vapor of the liquid in equilibrium with the liquid at a given temperature is called vapor pressure of liquid.
  • Boiling point: – The temperature at which the vapor pressure of a liquid becomes equal top one atmospheric pressure is called boiling point or the temperature at which the vapor pressure of a liquid becomes equal to its external pressure is called boiling point.
  • Freezing point: – The temperature at which both solid and liquid phases of a substance co-exit. The decrease of temperature of a liquid causes freezing.
  • Diffusion: – The process of intermixing of two liquids is called diffusion. The rate of diffusion becomes faster at higher temperature due to the movement of molecules of a liquid under the process of diffusion.
  • Mobility: – The power to the flow of a liquid is called its mobility. The case of flow of liquids depends upon the strength of the intermolecular attractive forces greater is the mobility of a liquid.
  • Density: – Density is that property of a liquid which tells us how heavy one substance is as compared to others.

The Solid State

Solids have definite volume and definite shape on ordinary temperature. They tend to maintain their definite shape and volume even at deforming forces.

Q10.  Describe general characteristics of solids.

Ans.    Following are the general characteristics of solids.

  • Definite shape: – The particles of a solid substance are held together in a definite and fixed pattern. There are strong forces of attraction between them. Hence solid have definite shape.
  • Compressibility: – Solids are almost incompressible. The compressibility of solids is about 10-6 times that of the gases.
  • Effect of heat:- During heating, the particles of a solid start vibrating with greater frequency this makes the molecules a little bit apart from each other. This process increases the volume of solids. Thus we say that solids expend on heating on further heating a stage reaches when the particles leave their fixed positions and start moving in the form of a liquid state.
  • Melting point: – The temperature at which a solid substance is converted into a liquid is called its melting point. When a solid is heated. Its temperature goes up the kinetic energy of the particles increases. Further increase in temperature breaks the clumps into individual particle. The entire energy is used up to make the particles of a solid to leave their fixed positions.
  • Diffusion: – The rate of diffusion of solids is very slow as compared to liquids or gases. The reason is that the constituent particles in solids are closely packed. There is very little space to permit the movement of the particles. Thus in solids diffusion is extremely small.
  • Density: – Solids have very high mass-to-volume ratio as compared to liquids and gases. Hence their densities are much higher than those of gases. Any how, the density of a solid is not far away from its liquids state.

Q11.  Describe various types of solids.

Ans.    Based on their structural feature, the solids are divided into two classes. These are:

  • Amorphous solids: – Amorphous solids are those in which atoms, ions or molecules are not arranged in a definite pattern, rather these are randomly arranged e.g. plastics, glass, rubber etc.
  • Crystalline Solids: – The solids in which atoms molecules or ions are arranged in a regular repeating three dimensional well ordered pattern are called as crystalline solids e.g. NaCl and AgNO3.

Q12. Define Allotropy.

Ans.    The phenomenon of the existence of an element in different forms, which have different physical properties, but same chemical properties is known as allotropy. Different forms of an element are called its allotropies e.g. Carbon, Sulphur, Tin, Oxygen and Phosphorous etc show allotropy.

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