How can physical properties be used to separate a mixture?

Think about the example of a mixture of salt water. The salt is a non-volatile ionic compound - this means it is very difficult to turn salt into a gas. It takes very high temps just to melt the salt.

The water is a volatile molecular compound which can be heated to the boiling point fairly easily. This leads to vaporization which turns the liquid water into steam.

So heating a solution of salt water allows you to separate the water from the salt.

Here is a video of an experiment which uses distillation to purify water from a solution of salt water.

Video from: Noel Pauller

Some other examples of techniques which can separate the components of a mixture using the differing physical properties of the substances in the mixture include:

Filtration
The video below shows how filtration can be used to separate calcium carbonate (chalk) from water.

video from: Noel Pauller

Chromatography
Here is a video which shows a paper chromatography experiment which was conducted to separate the pigments found in a black overhead marker.
video from: Noel Pauller

Hope this helps!