States of Matter (Solids, Liquids & Gases)

Definition of Matter: Everything around us which has mass and occupies space and can be felt by one or more of our five sense organs (Nose-smell, Ear-hear, Eyes-see, Tongue-taste and Skin-touch) is called matter e.g. clothes, stones, leaves, iron, wood, plastic, water, petrol, honey, air etc.

  • Branch of science which deals with study of structure, composition and properties of matter is called Chemistry.
  • Earlier three basic types of matter were studied i.e. solids, liquids and gases but now two more types of matters being explored Plasma and Bose Einstein Condensate. This means there are five types of matter.
  • Electricity, Magnetism, Heat, Light, Sound etc. are not considered matter as they neither have mass nor occupy space.
  • On the basis of physical appearance matters are classified as solids, liquids and gases.
  • On the basis of chemical composition matters are classified as elements, compounds and mixtures.
  • Matter is not continuous as we see with our naked eyes e.g. a log of wood or an iron bar is not continuous as seen but is actually made up of a number of extremely tiny particles joined together these tiny particles are called atoms or molecules.

Kinetic Theory of Matter

(a). Large number of tiny particles joins to form a matter but there is always some space left between these particles e.g. if we take 10 ml of water in a test tube and then dissolve small amount of common salt (NaCl) in it we will see level of water is still 10 ml and has not raised. This shows that small particles of salt have not occupied any extra space in the test tube but they have occupied the already existing gaps (Voids) between particles of water hence no change in effective volume of water.


(b). Particles of matter are in state of continuous movement. Degree of movement of particles depends upon closeness, strength of bonding and density of particles. Solids have least movement of particles (vibration only) whereas liquids have more movement and posses property to flow (hence also called fluids) & have significant vibrational, translational and rotational movement of particles. Movement of particles is maximum in gases and posses all kinds of motions and also have maximum fluidity. Due to lesser space between constituent particles in solids and liquids they are collectively called as condensed phase of matter.

(c). Constituting particles of matter attract each other and stronger the attraction closer the particles are and thus have stronger bonding between particles which leads to solid structures e.g. iron bar. LLiquids have relatively lesser attraction between the particles hence particles are loosely held and tend to flow e.g. water, honey, oil etc. Gases have least attraction among their particles hence posses maximum fluidity (movement) e.g. aroma of deodorant.

Graham’s Law of Diffusion of Gases

Rate of diffusion of gases is inversely proportional to square root of their molecular weight or density. Also in a vertical container, diffusion of gases from top to bottom or bottom to top does not depend on gravity.

Graham's Law of Diffusion

Close packing Particles are very closely packed Less closely packed, interparticle distance more than solids but less than gases Very loosely packed, particles are free to move with maximum interparticle distance
Force of attraction among particles Strongest Weaker than solids but stronger than gases Weakest
Shape & volume Definite shape and definite volume No definite shape but definite volume Neither definite shape nor volume
Compressibility Incompressible Almost incompressible Highly compressible
Motion of constituting particles Only vibration motion along their mean position Particles have greater freedom of movement, posses rotational, translational and vibrational motion Particles have maximum freedom of movement and posses very high rotational, translational and vibrational motion
Density Very high Lower than solids but much more than gases Very low density
Diffusion Normally do not diffuse Show property of diffusion and solids, liquids as well as gases can diffuse in liquids Diffuse very rapidly
Energy Minimum energy in particles. Energy increases with rise in temperature Intermediate energy and energy increase with rise in temperature Posses high energy and energy increase with rise in temperature
Example Wood, iron bar, chalk, ice etc Water, honey, oil etc Oxygen, carbon dioxide water vapours etc