As part of a school experiment to determine pollution levels, a boy was asked to collect a sample of air from the industrial area of the city. He was given a glass container with a removable but tight-fitting lid.
The boy knows that the jar contains air from the school environment. How will he ensure that this air does not get mixed with the air he collects from the industrial area?
He fills the container with water to drive out the air from it. He empties the water when he reaches the industrial area.