Which is a characteristic of an ideal gas?

The Five Main Points of Kinetic Molecular Theory are: 
1. A gas consists of a collection of small particles traveling in straight-line motion and obeying Newton's Laws. 
2. The molecules in a gas occupy no volume 
3. Collisions between molecules are perfectly elastic (that is, no energy is gained or lost during the collision). 
4. There are no attractive or repulsive forces between the molecules. 
5. The average kinetic energy of a molecule is directly proportional to the temperature (KE = 3/2RT) 

Thus a characteristic of ideal gas is "That the molecules of an ideal gas do not attract to each other"

The teacher is mostly talking about the distillation of a mixture