2 The atmosphereP. 1 / 1

Chapter 2 The atmosphere2.1 Getting to know our planet Earth

2.2 The atmosphere

2.3 Separation of oxygen and nitrogen from air

2.4 Properties of oxygen

2 The atmosphereP. 2 / 1

An introduction to the EarthAn introduction to the Earth

Fig. 2.1 Our planet Earth.

The Earth provides us with all the materials necessary for life.

2 The atmosphereP. 3 / 1

The atmosphere and airThe atmosphere and air

The atmosphere is a gaseous layer (about 80 km thick) surrounding the Earth.

2 The atmosphereP. 4 / 1

The gases in the atmosphere are held around the Earth by gravity.

Example 2.1Example 2.1 Class practice 2.3Class practice 2.3

makes

up

(a gaseous mixture) (atmosphere)

2 The atmosphereP. 5 / 1

Composition of airComposition of air

Air is a Air is a mixture ofmixture of

nitrogen

(78%)

nitrogen

(78%)oxyge

n(21%)

oxygen

(21%)

water vapourwater vapour

other gasesother gases

2 The atmosphereP. 6 / 1

Fig. 2.2 Percentage composition by volume of clean air.

1% other gases, including argon (0.93%) carbon dioxide (0.03%) small amounts of water vapour

nitrogen 78%

oxygen 21%

Activity 2.1Activity 2.1Class practice 2.4Class practice 2.4

2 The atmosphereP. 7 / 1

How can How can nitrogen and nitrogen and oxygen be oxygen be separated separated from air?from air?

????

2 The atmosphereP. 8 / 1

The components of air can be separated according to their differences in boiling

points.

The air is first liquefied by repeated cooling and compression.

The liquid air is then warmed up bit by bit very slowly. Different gases in air boil at different temperatures, we can collect them one by one.

This process is called fractional distillation of liquid air.

2 The atmosphereP. 9 / 1

Fig. 2.4 An air separation plant.

Class practice 2.5Class practice 2.5

2 The atmosphereP. 10 / 1

AIR

Argon Others e.g. helium, neon, water vapour

Properties

________________of liquid airfractional distillation

78% 21% 0.93% 0.03%

Nitrogen Oxygen Carbon dioxide