Atmosphere الغلاف الجوي
• The atmosphere is composed of a mixture of gases surrounding the Earth.
• These gases are Oxygen , Nitrogen , Carbon dioxide and other gases.
• They are attracted to the Earth by gravity.
• The atmosphere protects the Earth by absorbing ultraviolet radiation coming from outer space







Give reason:
Although oxygen is consumed during respiration, its percentage remains stable in the atmosphere.
Because of the sustainability of photosynthesis.

Preparation of oxygen in the laboratory
* Oxygen is created by displacing the water downward الماء لأسفل إزاحة in the flask during preparation at the laboratory.
Because the oxygen is heavier than the air












The importance and uses of oxygen:
1- Water consists of oxygen united with hydrogen.
2- It is important for respiration.
3- It is important for food combustion processes عملیة حرق الغذاء
inside living cells.
4- It is forming ozone layer O3 that protect the Earth from harmful radiation that comes from the sun.
5- Oxygen gets compressed in iron cylinders and used in:
1. Mechanical ventilation التنفس الصناعى for patients للمرضى who suffer from breathing difficulties.
2. During surgeries.
3. During diving and climbing mountains because oxygen becomes lighter when we have rise above the Earth’s surface.
4. Oxygen is also used in cutting and welding metals لحام المعادن



N.B
when combined with acetylene gas غاز الأسیتیلین to produce “oxy-acetylene” flame whose temperature reaches 3500°C sufficient to melt لصھر metals.

The properties of oxygen
oxygen is a colorless, tasteless and odorless gas.
• It scarcely نادرًا dissolves in water.
• Oxygen does not burn, but it helps in
burning.
• It has a neutral effect on litmus paper
with its two colors . U
3Burning ( Combustion) : It is a rapid unite اتحاد سریع of
oxygen with another element producing heat and light.
Atmosphere
Oxidation : It is a slow unite of oxygen with another
element in the presence of moisture (water).

G.RThe atmosphere has a great importance for the continuity of life on the planet.
Because the atmosphere protects the Earth by absorbing ultraviolet radiation coming from outer space.



Co2 percent 0.03 ٪ of the atmosphere.
- Its molecule consists of one carbon atom
linked with two oxygen atoms.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
- Carbon dioxide is emitted ینبعث as a result of the
combustion of organic materials such as: wood ,
coal , oil and tobacco.
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
- Carbon dioxide is produced from the
respiration of humans (the exhaled air).
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
- It turbids the clear limewater.
Preparation of Carbon dioxide






:040vk0: