The Air Around You

Section 15:1

Composition of the Atmosphere

Complete the following statement:

The atmosphere consists 78% of what gas?

Composition of the Atmosphere

• Nitrogen 78%

• Oxygen 21%

O O

Composition of the Atmosphere

• Other gases 1%

Argon

Carbon Dioxide

Water Vapor

Helium

Neon

Methane

Hydrogen

Ozone

Composition of the Atmosphere

Properties of Air

• Does air have mass?

• How can we show that air does have mass?

Watch YouTube video on bhoelzle.wikispaces.com

VideoEgg in bottle

Properties of Air

Density =

Mass

Volume

Because air has mass it also has other properties including:

Pressure – force pushing on an area or surface

Measuring Air Pressure

• Mercury Barometer – glass tube and a

dish of mercury

Pressure is measured by measuring the height of the mercury

Measuring Air Pressure

• Aneroid Barometer – airtight chamber

connected to a dial by a series of

springs and levers

Measuring Air Pressure

• Weather reports use several units for pressure

Millimeters of mercury

Inches of mercury

Millibars 1in = 33.87mb

Altitude and the Properties of Air

• Altitude- Distance above sea levelAs altitude increases

Air pressure decreases

Lower air pressure

Higherair pressure

There is less weight of air molecules on you as you climb the mountain

Altitude and the Properties of Air

• As air pressure decreases,

so does density

• Video