OXYGEN

What is the atmosphere?


It is a mixture of gases attracted to the earth by gravity

What is the importance of the atmosphere?
1-it protects the earth from ultraviolet radiation by absorbing it

2-It adjusts the earth temperature
3-dust particles which are pollutants help in condensation of water vapor and formation of rain and snow

oxygen gas
It represents 21% or 1/5 from the atmosphere
Structure of oxygen
Each molecule consists of two oxygen atoms


Source of oxygen

Green plants are the main source of oxygen give reason

Give reason: the percentage of oxygen gas in the atmosphere remains fixed
Because the consumed oxygen during respiration and combustion processes is compensated by green plants during photosynthesis

What is the percentage of oxygen in atmosphere?

Oxygen preparation in the lab


Hydrogen peroxide + manganese dioxide(catalyst)
 oxygen = water
Catalyst it is a chemical substance that remains without any change in its quantity and structure during the reaction

Give reason : oxygen is collected by downward displacement of water

Because oxygen scarcely dissolves in water

Properties of oxygen:

1-oxygen is colorless , odorless and tasteless

2-it scarcely dissolves in water

3-oxygen does not burn but helps in burning



4-Oxygen is heavier than air as it replaces the air
5-Oxygen combines with lighted magnesium ribbon to form magnesium oxide (white matter)



Oxygen combines easily with metals(oxidation)

Burning rusting
Rapid reaction with oxygen slow reaction with oxygen in to produce heat and light presence of moisture
The wire becomes heavier after burning because oxygen combines
With iron forming iron oxide


Give reason:

We have to paint bridges pillars

To avoid erosion of ironware by rust when it combines with oxygen and moisture


Importance of oxygen: in nature
1-the water molecule consists of an oxygen atom and two hydrogen atoms

2-it is important for respiration and combustion of food

3-ozone is composed of three atoms of oxygen which forms the ozone laye r



Uses of oxygen gas: in industry
1-mechanical ventilation for patients who suffer from breathing difficulties



2-during surgeries
3-during diving and climbing mountains (give reason)
Because oxygen is heavier than air so it becomes less when we go higher

4-it is used in cutting and welding metals

Oxygen combines with acetylene to produce oxy acetylene flame whose temperature reaches 3500 degree celsius