Matter – Nature and Behavior – Important Terms
The mass per unit volume of a substance is called density.
Kinetic Energy (K.E.):
The energy possessed by a particle by virtue of its motion is called kinetic energy Kinetic energy of particles in solid state is very less.
The force per unit area is called pressure.
Units of pressure:
The common unit of pressure is “millimeter of mercury” i.e., mm of mercury (mm-Hg) or just mm.
The mm of mercury pressure is also called torr.
1 torr = 1mm Hg
Another common unit of pressure is Atmosphere.
1 Atmosphere is that pressure which supports a column of mercury 760 mm Hg at 0°C at sea level.
1 atmosphere = 760 mm Hg
The S.I. Unit of pressure is pascal (Pa).
= 1.013xl05 Pa
Another unit of pressure used is bar. It has been derived from S.I. Unit of pressure.
1 bar =105 N/m2
1 atm=1.013 bar
Unit of volume
: The S.I. unit of volume is “cubic meter” which is written as m3.
l m3=106 cm3·
Temperature of a gas:
The molecules of a gas are in motion and posses kinetic energy. Therefore, the temperature of a gas is an indication of the average kinetic energy of gas molecules.·
Units of temperature:
The common unit of temperature is “degree celsius ” or “degree centigrade” which is written as
The S.I. unit of temperature is Kelvin which is denoted as K (letter K).
0°C = 273.16K
Melting point of solid:
The constant temperature at which a solid changes to a liquid is called its melting point. Melting point of ice is 0°C or 273.16 K.
Melting point of a solid is an indication of the strength of the intermolecular forces of attraction.·
Latent heat of fusion:
The amount of heat energy that is required to change 1 kg of a solid into a liquid at atmospheric pressure without any change of temperature at its melting point is known as Latent heat of fusion.·
The constant temperature at which a liquid changes into gas/vapour is known as its boiling point. Boiling point of water is 100°C or (273 + 100) = 373 K.·
Latent heat of vapourisation:
The amount of heat energy that is required to change 1 kg of a liquid into gaseous state at atmospheric pressure without any change of temperature at its boiling point is known as Latent heat of vapourisation.
· The smallest particle of an element is called an atom, i.e., matter is made up of particles.·
The smallest particle of an element that may or may not have physical existence is called atom.·
This is the process of intermixing of particles of two substances on their own. On heating the process of diffusion increases.·
Standard Temperature and Pressure (S.T.P.)
Standard Temperature = 0°C or 273 K
[t°C = (273 + t) K]
Standard Pressure = 1 atmosphere = 760 mm of Hg.