Today, I learned about Ideal gas and Real gas. There is a difference. Ideal gas is where the gas has negligible volume and intermolecular forces. Where as in Real gas, there is significant amount of volume and intermolecular forces. Intermolecular forces in Real gases is significant due to the condition that is high pressure. When pressure is high, molecules of gases is near to each other. 
I understand the lecture. But, there are a few questions that I couldn't manage to get a right answer. So I must revise it back.