States of Matter

Excerpt – Matter in our Surroundings covers topics like what is matter, characteristic properties of matter, States of Matter, Change of State of matter and Evaporation. We cover all these topics in depth. If you have any queries due leave them at the comments. We will positively answer it. Also sharing is caring. Share these notes with friends in facebook.

Matter- Its Physical Nature

Matter is anything which occupies space and has mass. Matter is made up of particles (atoms or molecules).

Characteristics properties of the particles of Matter

(1) Particles of matter have spaces between them. Eg. Sugar/ salt dissolve in water without raising the volume of water because sugar/salt go into the spaces between the water molecules.

(2) Particles of matter are continuously moving. Eg. We can get the odour of the perfume/agarbatti sprayed in one corner to the other corner of the room due to the kinetic energy possessed by the particles.

(3) Particles of matter attract each other. Due to forces of attraction between the particles we have different states of matter.

(4) Particles of matter are so small to be seen with naked eyes. Notice that a crystal of potassium permanganate gives colour even on repeated dilutions.

States of Matter

Matter around us exists in three states — solid, liquid and gas.

These three states differ from one another due to the difference in the size of spaces in between the constituent particles (intermolecular spaces) and their forces of attraction.

Since forces of attraction are inversely proportional to the spaces in between the constituent particles, therefore the forces of attraction between the constituent particles are the strongest in solids, intermediate in liquids and weakest in gases.

On the account of the above differences – solids, liquids and gases differ in the following respects:-

 PackingInterparticle DistancesInterparticle forces of attractionShape and VolumeCompressibility Rigidity/ Fluidity EnergyDensityDiffusion
Solid Constituent particles are very closely packed.Interparticle distances are the smallest.Interparticle forces of attraction are the strongest.They have a definite shape and definite volume. Completely incompressibleHave rigidity. Constituent particles have minimum energy.Constituent particles have high density. They generally do not show the property of diffusion.

Constituent particles are very loosely packed.Interparticle distances are larger than those in solids but smaller than those in gases. Interparticle forces of attraction are weaker than those in solids but stronger than those in gases.They do not have a definite shape but have a definite volume. Almost incompressibleHave fluidity, lower than that of gases.Constituent particles have energy greater than those of solids. Constituent particles have density lower than those of solids but much higher than those of gases. They show the property of diffusion.
GasConstituent particles are free to move about. Interparticle distances are the largest. Interparticle forces of attraction are the weakest. They neither have a definite shape nor volume.Highly compressible.Have the highest fluidity. Constituent particles have highest energy. Constituent particles have very low densities. They diffuse rapidly.

(i) Rigidity is the tendency to maintain shape when some outside force is applied.

(ii) Compressibility is the tendency to decrease volume when some outside force is applied.

(iii) Fluidity is the tendency to flow.

(iv) Kinetic energy is the energy possessed by particles due to motion.

(v) Density is mass per unit volume.

(vi) Diffusion is the intermixing of the particles of different states of matter on their own.

Diffusion, as well as the kinetic energy of the particles, increases with an increase in temperature and vice versa. That is why the odour of hot sizzling food reaches far off places.

Change of State of Matter

The states of matter are inter-convertible by changing temperature or pressure or both.

  • SOLID [Melting/Heating/Fusion (High Temperature, Low Pressure)]  →  LIQUID [Boiling/Heating/Vaporisation (High Temperature, Low Pressure)])  →  GAS
  • SOLID [Freezing/Cooling/Solidification (Low Temperature, High Pressure)] ← LIQUID [Cooling/Condensation (Low Temperature, High Pressure)] ← GAS
  • SOLID ← [Sublimation (Cooling) | Sublimation (Heating)] →  GAS

(1) Melting point is the temperature at which solid melts to become a liquid at atmospheric pressure. The process of melting (change of solid into liquid state) is also called Fusion.

(2) Freezing point is the temperature at which a liquid freezes to become a solid at atmospheric pressure. The process of freezing (change of the liquid into solid state) is also called Solidification.

(3) Boiling point is the temperature at which a liquid starts boiling at the atmospheric pressure(1 atm).

(4) High melting point or boiling point indicates the inter-particle force of attraction is strong while low melting point or boiling point indicate that interparticle force of attraction is weak.

(5) Condensation is the process of changing a gas/vapour to a liquid by cooling.

(6) Sublimation is the direct conversion of a solid into the gaseous state on heating and vice-versa without going into the liquid state.

(7) Latent heat of Fusion is the amount of heat required to change 1 kg of a solid into liquid at atmospheric pressure at its melting point.

(8) Latent heat of Vaporisation is the amount of heat required to change 1 kg of a liquid into vapours at atmospheric pressure at its boiling point.

(9) SI unit of temperature is Kelvin (K), K = °C + 273


The phenomenon of change of a liquid into its vapours at any temperature below its boiling point is known as evaporation. It is a surface phenomenon. It is a continuous or ongoing process which occurs at a much slower rate.

Evaporation causes cooling as some of the particles on the surface of the liquid which have high kinetic energy overcome the forces of attraction by the neighbouring particles, leave the liquid surface and get converted into vapours. So, the remaining particles have less average kinetic energy, hence the temperature decreases.

(i) Boiling is a bulk phenomenon. Particles from the bulk (whole) of the liquid change into vapour state.

(ii) The amount of water vapour present in the air is called Humidity.

(iii) The process of evaporation of water from aerial parts of plants especially leaves is known as transpiration.

The rate of evaporation is affected by the surface area exposed to atmosphere, temperature, humidity and wind speed.

(i) Evaporation increases with an increase in the exposed surface area and vice-versa.

(ii) Evaporation increases with an increase in the temperature and vice-versa.

(iii) Evaporation increases with an increase in the wind speed and vice-versa.

(iv) Evaporation decreases with an increase in the humidity and vice-versa.

Plasma – It is the fourth state of matter consisting of super-energetic particles in the form of ionised gases. The fluorescent tube, neon sign bulbs consist of plasma. The plasma is created in stars due to high temperature.

Bose-Einstein Condensate (B.E.C) – It is the fifth state of matter which is formed from matter that has been cooled to near absolute zero (-273°C) thus the velocities of atoms decreases causing individual atoms to overlap forming a single super atom. For eg: – a rotating B.E.C could be used as a model black hole, allowing light to enter but not to escape.

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