## STATES OF MATTER-I-GASES

## KEY POINTS:

### 1. Kinetic molecular theory:

The kinetic molecular theory was postulated by Daniel Bernoulli, it explains the behavior of gases based on the movement of molecules.

### 2. Boyle's law:

According to Boyle's law, the volume of a fixed amount of a gas is inversely proportional to applied pressure at constant temperature and the number of moles.

\[V \propto \frac{1}{p}\; (When\; T\; and\; n\; are\; constant\; )\]

### 3. Charle's law:

According to Charle's law, the volume of a fixed amount of gas is directly proportional to absolute temperature at constant pressure and the number of moles.

\[V \propto T\; (When\; P\; and\; n\; are\; constant\; )\]

### 4. Avagadro's law:

According to Avagadro's law, the volume of a fixed amount of gas is directly proportional to the number of moles at constant temperature and pressure.

\[V \propto n\; (When\; P\; and\; T\; are\; constant\; )\]

### 5. Graham's law of diffusion or effusion:

According to Graham's law, the rate of diffusion or effusion of a gas is inversely proportional to the square root of density or molar mass of gas at constant temperature and pressure.

\[r \propto \frac{1}{\sqrt{d}}\;\;\;\; or \;\;\; r \propto \frac{1}{\sqrt{M}}\;\]

### 6. Dalton's law of partial pressure:

According to Dalton's law of partial pressure, the total pressure exerted by a mixture of non-reacting gases is equal to the sum of their partial pressures.

### 7. Absolute Zero:

It is a hypothetical temperature at which the volume of an ideal gas becomes zero. Its value is -273.16 degrees Celcius or zero kelvin.

### 8. General gas equation:

It is also called an ideal gas equation.

**PV=nRT**

### 9. Van der Waal's equation:

It is also called as real gas equation.

\[\left ( P\; + a\frac{n^2}{V^2} \right )\left ( V\;-\;nb \right )\; = \;nRT\]

### 10. Joule Thomson effect:

The sudden expansion of highly compressed gases into a region of low pressure causes cooling.

### 11. Ideal gas:

Gases that obey Boyle's and Charle's law at all conditions are ideal. There are no forces of attraction between molecules of an ideal gas.

### 12. Non-ideal gas or real gas:

Gases that obey Boyle's and Charle's law at all conditions are ideal. There are no forces of attraction between molecules of an ideal gas.

### 13. Plasma:

Plasma is a mixture of positive ions; negative electrons and neutral atoms. It is also called the fourth state of matter.