Class 9, Science, Chapter-1, Lecture-1, States of Matter (Notes)
Matter:
Something which has mass, occupies space and can be sensed is called matter.
Characteristics of Matter:
- Matter is composed of particles
- The particles of matters are very small
- The particles of matter have space between them
- The particles of matter are in constant motion
- The particles of matter attract each other
Density:
The mass per unit volume of a substance is termed as its density
Mathematically, ${\rm{d = }}{{\rm{m}} \over {\rm{v}}}$
Where, d = density
m = mass
v = volume
Density is a SCALAR
S.I. unit is ${\rm{kg}}{{\rm{m}}^{{\rm{ - 3}}}}$
Commonly used unit is ${\rm{g}}{\left( {{\rm{cm}}} \right)^{{\rm{ - 3}}}}$ or ${\rm{g}}{\left( {{\rm{mL}}} \right)^{{\rm{ - 1}}}}$${1c{m^3} = 1mL}$
Diffusion:
The intermixing of particles of two different substances on their own is called diffusion.
Osmosis:
The movement of solvent molecules through a semi-permeable membrane into a region of higher solute concentration, to equalize the solute concentrations on the two sides is termed as osmosis.
Osmosis is a special kind of diffusion:
Justification:
During diffusion, particles of different substances (solute and solvent) move and intermix to make the concentration homogeneous.
During osmosis, only the solvent particles move through a semi permeable membrane from lower solute concentration to equalize the concentration on both sides.
So, osmosis is a special kind of diffusion.
Cohesion:
The force of attraction by which the particles of a matter are bound to one another is termed as cohesion.
Classification of Matter: (on the basis of physical state)
- Zero state (Bose-Einstein Condensate: BEC)
- Solid
- Liquid
- Gas
- Plasma
- Beam
- Wave
Change of State:
Example of Co-existence of Solid-Liquid-Gaseous state:
Water exists in all the three states at temperature 0.01 0C and at pressure 4.58 mm of Hg
Melting (Fusion):
The process in which a matter changes its state from solid to liquid at a fixed temperature without any change in its temperature is termed as melting or fusion.
Melting Point:
The fixed temperature at which a solid melts to become a liquid at atmospheric pressure (760 mm of Hg) is called its melting point.
Latent heat of fusion:
The amount of heat (energy) required in converting unit mass of a solid into liquid at a given temperature and pressure without any change in temperature of the substance is called the latent heat of fusion of the substance.
- S.I. unit is J kg-1.
The Latent heat of fusion of ice at 0 OC and 1 atmospheric pressure is 334 kJg–1:
Meaning: The quantity of heat required to convert 1 g of ice into water at 0 OC and 1 atmospheric pressure without any change in temperature is 334 kJ.