The chemical substance we are dealing with here is water. On a very cold day if a person does not have their windshield defrost on, raindrops falling from the sky onto the freezing windshield will turn into ice. When this happens, water is going from a liquid state to a solid state. This process is the act of freezing.
Condensation is the act of a substance changing from a gaseous state to a liquid state. An example of this in a driving situation is when you are driving on a very damp, cold day without the air conditioning compressor turned on. The damp air inside the car comes into contact with the cold windshield and fogs up the glass. This is the act of condensation, where the water vapor in the air turns into liquid micro-droplets on the windshield. Turning the compressor dries out the air inside the car, thus eliminating the condensation on the windshield obstructing your view.