The amount of mass of a substance in a given volume
pressure
The amount of force pushing on an area.
altitude
Elevation above sea level
pollutants
Harmful substances in air, water, or soil.
baromet
An instrument used to measure changes in air pressure
mercury barometer
An instrument that measures changes in air pressure, consisting of a glass tube partially filled with mercury, with its open end resting in a dish of mercury.
photochemical smog
A brownish haze that is a mixture of ozone and other chemicals, formed when pollutants react with each other in the presence of sunlight.
air pressure
The pressure caused by the weight of a column of air pushing down on an area.
aneroid barometer
An instrument that measures changes in air pressure without using a liquid.