The Earth's Atmosphere
The atmosphere is made up of a blanket of gases surrounding the Earth. We live in the troposphere. Weather occurs in this layer. When we fly in commercial jets, we're in the stratosphere. The mesosphere is where only astronauts have passed and the ionsphere is the highest layer which consists of mostly charged particles.
What Does Air Consist Of?
- Nitrogen - 79%
- Oxygen - 20%
- Others ( CO2, Other Noble gases, Water Vapour)
The Ozone Layer
Ozone has the formula O3, it consists of 3 oxygen atoms. It is formed when Ultraviolet Radidation from the sun breaks down the oxygen molecules into atoms. Thes atoms react with other oxygen atoms to form ozone.
Ozone molecules protect us by absorbing the harmful ultraviolet radiation and break down into oxygen atoms agin. The energy produced when new bonds are formed is heat, therefore the ozone layer is warmer than the air below it.
Measuring The Amount Of Oxygen In Air
Apparatus: A tube of hard glass rod is connected to two gas syringes A and B. The tube is packed with small pieces of coper wire. One syringe containes 100 cm3 of oxygen and the other is empty.
The Method:
- The tube is heated by the bunsen burner. When A's plunger is pushed inwards, the ai is forced through th etube and into B. The oxygen reacts with the hot copper and turns it black. When A is empty, B's plunger is pushed in, forcing air back into A. Repeat the cycle a few ore times.
- Heating is stopped after 3 minutes and the apparatus is allowed to cool. All the gas is then pushed into one syringe and its volume measured.
- Steps one and two are repeated until the volume of the gas remains steady. This means that all the oxygen have been used and the final volume is recorded.
The results:
Starting volume: 100 cm3. Final Volume: 79cm3
Vol. of oxygen in 100cm3 of air will be 21cm3.
Percentage of oxygen in air is 21/100 x 100 = 21%
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