Grade 10 Science Related Reading/Chemistry
Chemistry Gr10
Name:____________________
Class:____________________
Date:____________________
Chlorinated
hydrocarbons
The Earth’s
Blanket
and their uses
Task 1 – Pre-Reading Activity
Here are some fact statements about ozone which need to be completed correctly:
1. Ozone is made of ___________________ oxygen atoms.
2. Ozone is less stable than diatomic oxygen, so it tries to give up
______________________________________.
3. We see ozone as a ______________________ gas ( color).
4. Ozone is described as __________________________________ ozone and
___________________________________ ozone.
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Task 2 – Reading Activity
The Ozone Hole. The Ozone Hoax. Pollution. Skin Cancer. The topic of ozone makes
headlines on a regular basis, but why does a single molecule merit such media coverage?
How important is the ozone in our atmosphere and why are scientists so concerned about
its increase near the surface of the earth and its disappearance higher up in the
atmosphere?
First things first - what is ozone? Ozone is made of three oxygen atoms (O3). The oxygen
we find in our atmosphere is made up of two oxygen atoms (O2). Because of its chemical
formulation, a single atom of oxygen (O) is unstable. That is, it wants to combine with
something else. That is why oxygen is almost always found in pairs, in its O2 (diatomic)
form, where it is more stable. O3 is less stable than O2, because it wants to return to the
diatomic state by giving up an oxygen atom. When ultraviolet (UV) radiation hits an
oxygen molecule, it may cause the molecule to break apart into single atoms of oxygen (O2
+ UV -> O + O). These atoms are very reactive, and a single oxygen atom can combine with
a molecule of oxygen to form ozone (O2+ O -> O3).
When enough ozone molecules are present, it forms a pale blue gas. It is an unstable
molecule that readily combines with other atoms. Ozone has the same chemical structure
whether it is found in the stratosphere or the troposphere. Where we find ozone in the
atmosphere determines whether we consider it to be good or bad.
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Ozone is found in two different layers of the
atmosphere - the troposphere and the
stratosphere. The stratospheric ozone, or
"good ozone," protects life on earth from
harmful effects of the sun's UV rays. We
have good reason to be concerned about the
thinning of the ozone layer in the
stratosphere. Tropospheric ozone, or "bad
ozone," is an air pollutant that damages
human health, vegetation, and causes many
respiratory problems. We have good reason
to be concerned about the buildup of ozone in the troposphere.
When old refrigerators, air conditioners and similar items are thrown away gases from
them called chlorofluoro carbons (CFC’s) rise up into the air and destroy the ozone. Most
countries no longer produce CFC’s but they can stay in the atmosphere for years and
destroy the ozone. Scientists in the 1980’s discovered a hole in the ozone layer and it was
growing. Scientists predicted an increase in risk due to sunburn, faster ageing of our skin ,
skin cancer and damage to our eyes such as cataracts. Each August a hole is formed over
Antarctica and it has doubled in size to that of North America since its discovery,
sometimes it extends over Southern Chile and Argentina. On some days people in Punta
Arenas, Chile ( world’s Southernmost city) may limit their sun exposure to no more than
20 minutes between noon and 3 pm , on other days they don’t go out at all.
There are special instruments to measure the thickness of the ozone layer, Scientists use a
unit called the Dobson Unit (abbreviated DU) to describe the amount of ozone in the
atmosphere.
The saying "Good up high and bad nearby," sums up ozone in the atmosphere.
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Key Vocabulary
ozone
oxygen
Ultraviolet
chlorofluorocarbons
stratosphere
troposphere
pollutant
hole
Dobson unit
A. Choose the correct answer for each of the following statements:
1. The hole in the ozone layer was discovered over
a. 10 years ago
b. 30 years ago
c. 50 years ago
d. 70 years ago
2. The sun’s harmful rays are called
a. Chlorofluoro carbons
b. ozone
c. CFCs
d. UV
3. Why do people in Punta Arenas sometimes avoid the sun?
a. They are allergic to ozone
b. They will get skin cancer
c. They will get a sun tan
d. They will die in 24 hours
4. Scientists are concerned about
Increase in ozone concentrations in the troposphere
Increase in ozone concentrations in the stratosphere
Increase in skin cancer
Increase use of chlorofluorocarbons
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B. Answer the following questions:
1. How is the ozone distributed in the atmosphere
__________________________________________________________________
__________________________________________________________________
2. Why is ozone called good and bad at the same time?
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
3. Why is the title of this passage called –The Earth’s blanket ?
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
4. What would happen if the ozone hole expands?
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
5. What saying sums up ozone in the atmosphere?
_________________________________________________________________
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C. Look at the illustration given below and write the correct numeral against each
statement given in the table below:
Statement
UV releases Cl from CFCs
More UV  More skin cancer
CFCs are released
Cl destroys ozone
Depleted ozone  more UV
CFCs rise into ozone layer
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Numeral
D. Which of the following pairs of statements about ozone is correct?
Tropospheric ozone
Stratospheric ozone
A. It is significantly affected
by increasing levels of CFCs.
It accumulates in high
concentrations to form the
ozone layer.
It is significantly affected by
increasing levels of CFCs.
It damages photosynthetic
organisms.
B. It causes health problems
in humans and animals.
C. It accumulates in high
concentrations to form the
ozone layer.
D. It damages photosynthetic It causes health problems in
organisms.
humans and animals.
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True / False
Task 3 – Post Reading Activity
The Chapman-cycle
Ozone is created and destroyed in the stratosphere. The English mathematician and
geophysicist, Sidney Chapman, investigated and described this cycle. Because of his work the
cycle is called the "Chapman-Cycle".
Add the missing words to the text.
The missing words are:
ozone molecule(s)
;
oxygen atom(s)
; oxygen molecule(s)
UV-light
; heat energy
;
1) High-energy (short wave) ultra-violet light can breakdown (crack)
_____________________ into _____________________.
2) If an _______________
, an _________________ __ and a heavy
weight particle impact in a “triple collision”, an
__________________________ is formed. The heavy weight
particle
can be a dust particle, or another big gas
molecule like nitrogen gas.
3) The heavy weight particle has the task, to absorb the
____________________ ,which becomes free during the ozone
formation. It delivers the __________________________ slowly to
the environment afterwards.
4) _____________________ can be cracked likewise by
_______________________.
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