Matter in Our Surroundings-II

Matter in Our Surroundings-II

Basis of Classification of Matter:

• Based upon particle arrangement
• Based upon energy of particles
• Based upon distance between particles

Solid	Liquid	Gas
Constituent particles are very closely packed.	Constituent particles are less closely packed.	Constituent particles are far apart from each other.
Force of attraction between particles is very strong.	Force of attraction between particles is less strong.	Force of attraction between particles is negligible.
Force of attraction between particles is very strong.	Kinetic energy between particles is more than that in solids.	Particles have maximum kinetic energy.
Have definite shape and volume.	Do not have definite shape but definite volume.	Neither have definite shape nor definite volume.
Have high density and cannot be diffused.	Density is lower than solids and can diffuse.	Density is least and can easily diffuse.
Incompressible.	Almost incompressible.	Highly compressible.

Rigidity: It is the state in which the particles of a substance are fixed in their positions.

Density: It is the packing of the constituent particles, in a given volume of the substance. It can also be defined as the mass per unit volume of a substance. It is expressed in kg/m^3.

Fluidity: It is the property by virtue of which, the particles of a molecule move in space. It is the ability of a substance to flow, for example, liquid and gases.

Kinetic Energy: The energy possessed by a body due to its movement or motion.

Compressibility: It is a property by which the volume of a substance can be reduced, or a substance can be made compact, by applying a force of pressure.

Change of State of Matter:

Physical states of matter can be interconverted into each other by following two ways:

1. By changing the temperature

2. By changing the pressure

1. Effect of Change of Temperature:

     a)      Solid to liquid:

• On increasing the temperature of solids, the kinetic energy of the particles increases which overcomes the forces of attraction between the particles thereby solid gets converted to a liquid.

• Melting: Change of solid state of a substance into liquid is called melting.
• Melting point: The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.

     b)      Liquid to gas:

• On heating a liquid like water, the kinetic energy of its particles increases as high as in a gas, thus causing the liquid to change to a gas.

• Boiling: The change of a liquid substance into gas on heating is called boiling.
• Boiling point: The temperature at which a liquid boils and changes rapidly into a gas at the atmospheric pressure is called its boiling point.

      c)      Gas to liquid:

• On cooling a gas like steam (or water vapour), the kinetic energy of its particles is lowered down, causing them to move slowly and bringing them closer, forming a liquid.

• Condensation: The process, in which a gas, on cooling, turns into a liquid at a specific temperature is called condensation or liquefaction.

      d)     Liquid to solid:

• When a liquid is cooled down by lowering its temperature, its particles lose the kinetic energy and come to a stationary position, causing the liquid to turn to solid.

• Freezing: The change of a liquid substance into solid by lowering its temperature is called freezing.
• Freezing point: The temperature at which the state of a substance changes from a liquid to a solid is called the freezing point of that substance.

Fusion: The process of melting, that is, change of solid state into liquid state is also known as fusion.

Latent heat: The heat energy that is required to change the state of a substance without causing any ruse in the temperature of the substance is called latent heat. Since, the heat energy is hidden in the bulk of the matter, it is called latent heat.

• Latent heat of fusion: The heat energy required to convert 1 kilogram of a solid into liquid at atmospheric pressure, at its melting point, is known as the latent heat of fusion
• Latent heat of vaporization: The heat energy required to convert 1 kilogram of liquid into gas, at atmospheric pressure, at its boiling point, is known as the latent heat of vaporization.

Sublimation: The change of state of a substance directly from a solid to gas or gas to solid, without changing into the liquid state, is called sublimation. 

2. Effect of change of pressure

• Gas to liquid: Gases can be liquefied by applying pressure and reducing the temperature. When a high pressure is applied to a gas, it gets compressed and if the temperature is lowered, the gas is liquefied.
• Solid CO₂ gets converted directly to gaseous state on decrease of pressure to 1 atmosphere without coming into liquid state. This is the reason that solid carbon dioxide is also known as dry ice.