The gases obey the different gas laws only theoretically. Practically all of them show some deviation from these laws. These are called real gases. The deviation are maximum under high pressure and at low temperature. These are comparatively small when the conditions are reversed. It has been found that the easily liquefiable gases show more deviations from the ideal gas behaviour as compared to the gases which are liquified with difficulty.
Gas deviates from ideal gas behaviour because molecules

Options

A. are colouless
B. attract each other
C. contain covalent bond
D. show Brownian Movement.

Explanation

To solve the question regarding why gases deviate from ideal gas behavior, we can break it down into a series of logical steps:

### Step-by-Step Solution:

1. **Understanding Ideal vs. Real Gases**:
- The ideal gas law is represented by the equation \( PV = nRT \), where \( P \) is pressure, \( V \) is volume, \( n \) is the number of moles, \( R \) is the ideal gas constant, and \( T \) is temperature.
- Real gases do not perfectly follow this law due to various factors, especially under certain conditions.

2. **Conditions for Deviation**:
- Real gases show maximum deviation from ideal behavior at **high pressure** and **low temperature**. Under these conditions, the assumptions of the ideal gas law (that gas particles do not interact and occupy no volume) break down.

3. **Factors Leading to Deviation**:
- The deviations occur primarily due to:
- **Intermolecular Forces**: At high pressures, gas molecules are forced closer together, and the attractive forces between them become significant, leading to a decrease in pressure compared to what would be expected from the ideal gas law.
- **Volume of Gas Particles**: At low temperatures, the volume occupied by gas particles becomes significant relative to the total volume of the gas, which also leads to deviations from ideal behavior.

4. **Real Gas Equation**:
- The real gas behavior is described by the Van der Waals equation:
\[ \left(P + \frac{an^2}{V^2}\right)(V - nb) = nRT \]
- Here, \( a \) accounts for the intermolecular forces, and \( b \) accounts for the volume occupied by the gas molecules.

5. **Conclusion**:
- Therefore, gases deviate from ideal gas behavior primarily because of the **intermolecular forces of attraction** between gas molecules and the **finite size of the gas particles**.

### Final Answer:
Gas deviates from ideal gas behavior because molecules experience intermolecular forces of attraction and occupy a finite volume.