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States of Matter Class 11: Overview

 In our everyday life, we can observe four different states of matter, namely solid, liquid, gas and plasma. However, there are numerous other states that can be seen to exist but only under extreme conditions. The ones worth mentioning are glass and Bose-Einstein condensates.

They are all differentiated on the basis of differences in their quality. For example, their characteristics can be stated as:

States of matter Volume Shape Particle position
Solid Fixed Fixed Close together and fixed
Liquid Fixed Not fixed. Adapts to the shape of the container. Particles close but move freely
Gas Variable Variable Particles not close or fixed
Plasma Variable Variable Neutral atoms, and large number of ions and electrons that move freely.

 States of matter

  • Solid: The particles, or the atoms, ions and molecules, are packed together closely. The particles are free to vibrate but are not free to move. They can only change their volume and shape when external force is applied, or when they are cut into smaller pieces,
  • Liquid: They are incompressible matter in liquid form that is not dependent on pressure. They have a fixed volume, if the pressure and temperature are kept unchanged. When solid is exposed to temperatures higher than their specific melting points, they have a tendency to transform into the liquid state, subject to pressure properties.
  • Gas: the particles in a gaseous state have enough kinetic energy in it so as to render the molecular forces to zero. The distance between the molecules is larger than their size itself. A liquid can be transformed to a gaseous state by heating it to the boiling point, keeping the pressure constant, or by decreasing the pressure, while keeping the boiling point constant.
  • Plasma: Plasma does not have a specific shape or volume and are electrically conducive. They produce magnetic fields and currents. A gas can be transformed into plasma by two methods: difference of high voltage between 2 points, or by giving exposure to high temperature. The plasma state does not really exist in abundance on earth and hence is usually misunderstood. Examples of activities that lead to generation of plasma are neon lights, lightening, plasma TVs etc.
  • Bose Einstein Condensate: it is a superfluid in gaseous state formed by atoms that are cooled to temperatures extremely close to zero.

Transition of States of Matter

As we have already discussed, states of matter can be transformed to one another under specific conditions. But before understanding those conditions, we need to discuss and define a few terms:

  1. Melting point: the specific temperature at which matter transforms itself from solid to liquid.
  2. Boiling point: the specific temperature at which the pressure of vapour of liquid equals the atmospheric pressure. Water starts boiling at 100 degree Celsius.
  3. Freezing point: the specific temperature at which matter transforms itself from fluid to solid.
  4. Evaporation: the specific temperature at which matter transforms itself from liquid to gas.
  5. Condensation: the specific temperature at which matter transforms from gas to liquid.

Measurable properties of gas

  1. It is denoted in kg or grams.
  2. The volume is denoted in liters, milliliters, centimeter cube, metre cube or decimeter cube.
  3. Pressure is measured with the help of a manometer or barometer.
  4. Temperature can be measured on Celsius or kelvin. The equation for conversion is T(K) = T(°C) + 273.15

What is an isobar?

It is a graph that measures volume on one axis and pressure on the other. For this, it is to be noted that the pressure is kept constant.

What is an isochore?

It is a graph of pressure on one axis and temperature on the other. For this, it is to be noted that the volume needs to be constant.

Some equation for gas

  • V is directly proportional to 1/p where T and n are constant (Boyle’s law)
  • V is directly proportional to T where p and n are constant (Charles’ Law)
  • V is directly proportional to n where p and T are constant (Avogadro’s law)
  • V is directly proportional to nT/p

= pV is directly proportional to nT

or pV = nRT

In all these equations, p= pressure, T= Temperature, N is the number of molecules and V is the volume.

Dalton’s Law of partial pressure

He said that when the temperature is kept constant, the total exerted pressure by a mixture of multiple non reacting gases can be taken as the summation of the partial pressures of the various gases present in the specific mixture.

P = p1 + p2 + p3 . . .

Graham’s law of diffusion

The rate of diffusion of various gases is inversely proportional to their density’s square roots.

r1 / r2 = √d2 / √d1

Kinetic theory of gases and its assumptions

  • Gas contains molecules
  • Volume occupied by these molecules is negligible
  • There are continuous rapid motion of these molecules and they collide with each other.
  • Molecules are perfectly elastic and there is absolutely no loss of kinetic energy
  • 0 attractive force
  • The pressure is due to collision of gas molecules with the wall of the container
  • Molecules have different velocities and energies.

KE = 3/2RT

Average kinetic energy per molecule = 3/2kT

Velocities of gas molecules

  1. Most probable: a = √(2RT/M)
  2. Average velocity: v = √(8RT/nM)
  • Root mean square velocity

Deviation from Ideal behavior

Compressibility factor (z) = pV / nRT

Van Der Waal’s equation and its limitations

where a and b are constants that have positive values and are the individual gas’s characteristics.

The limitation is the specific range of both pressure and temperature and hence tends to deviate at extremely high pressure and low temperature.

Liquid state and its properties

Vapour pressure is the pressure exerted by vapour over the liquid surface when these are in harmony with liquid at a given temperature. It depends on the nature of liquid, temperature, boiling point, surface tension and viscosity.

Thus the above is a brief guide for the different states of matter, their properties, and laws, equations and theories pertinent to them. Keep following us here to get more information on similar topics.

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