Lesson 1
14th Jan
by shuoyu
The 4 spheres of earth are Lithosphere, Hydrosphere, Biosphere and Atmosphere. In this lesson our main focus is on Atmosphere.
First we learnt about the structure of Atmosphere. The Atmosphere is divided into four layers.
◎The sphere where clouds exist is troposphere, the lowest layer of atmosphere.
◎Above troposphere is stratosphere, where ozone layer in this sphere reflects the ultraviolet rays from the sun.
◎Mesosphere is the third layer which reflects radio waves.
◎Thermosphere is the outermost layer. The temperature is high enough to burn the meteorites. -The temperature changes differently in each sphere (the Environmental Lapse Rate).
-Nitrogen (78%) and Oxygen (21%) are the main components. The Atmosphere provides the air we breathe and keep our planet warm.
I am still a bit confused about how the CFC damages the ozone layer. Maybe I should do some researches for some explanation (about the reactions that take place).
We also learnt about the carbon cycle by playing the game online. Carbon is absorbed by oceans, photosynthesis of plants and stored as trees, soils and fuel. At the same time is released by deforestation and human activities (breathing and burning fuel).
The quizzes enabled us to revise and improve our understanding of the new topic, saving the time to memorize at home. I think it was the most effective way to review immediately after learning.
Nitrogen cycle is our homework which will be tested the next lesson.
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Hi shuoyu, this is the answer to your question regarding CFCs and the ozone layer. Hope it helped you understand better.
ReplyDelete1) Although the ozone is produced and destroyed naturally, it stays in a nice equilibrium.It is formed when oxygen molecules absorb ultraviolet radiation with wavelengths less than 240 nanometres and is destroyed when it absorbs ultraviolet radiation with wavelengths greater than 290 nanometres.
2) The introduction of CFCs since the 1960s has however, disrupted the equilibrium when UV destroys its carbon-chlorine bond, producing a chlorine radical.CFCl3 + UV Light ==> CFCl2 + Cl
Cl + O3 ==> ClO + O2
ClO + O ==> Cl + O2
The free chlorine atom is then free to attack another ozone molecule
Cl + O3 ==> ClO + O2
ClO + O ==> Cl + O2
and again ...
Cl + O3 ==> ClO + O2
ClO + O ==> Cl + O2
and again... for thousands of times.
It is to be found that a single CFC molecule can destroy 100,000 ozone molecules and this indirectly lead to the Montreal Protocol signed in 1987 which signed by over 70 countries, aimed at reducing CFC production by 20% (relative to 1986 levels) by 1993 and by 50% by 1998.
url to animation of how the ozone is destroyed by CFCs : http://www.ucar.edu/learn/1_6_1.htm (3rd picture under heading:The Story of the Ozone Hole)
carolyn.