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Pressure
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Pressure CLIL: Science 3 4
Pressure
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Modules
Pressure
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A. What do you think will happen to a balloon if it is taken underwater?
B. Look at the highlighted words in the text and find their definitions in a dictionary.
C. Listen, read and check your answer to activity A. 
The easiest way to
Have you ever felt your ears pop when diving The easie s t w a y t o
unders
illing
y
illing
tand this is b
really deep underwater? What you felt was understand this is by illing
© MM Publications
a result of water pressure. There is more a balloon with air . D o this at
a balloon with air. Do this at
e
sur
sea le
e the pr
e
s
pressure underwater than there is on land. sea level, where the pressure
el, wher
v
v
is 1 atm. Then di
e under
w
er
When you dive down, the irst place you feel is 1 atm. Then dive underwater
at
the change in pressure is in your ears. This is with the balloon. Under w at er , the
with the balloon. Underwater, the
s
e will c
pr
because your ears always have air inside them. pressure will compress the air in the
s
s the air in the
ompr
e
e
sur
a
balloon in the same way it compresses the
balloon in the same w
se
s the
The higher pressure compresses the air, and balloon in the same w a y it c ompr e s se s the
s
y it c
ompr
e
. As the pr
ease
ease
e incr
s
, the
, the
s
s
e
e
s
e incr
sur
sur
. As the pr
air in our ears
air in our ears
this is what makes our ears feel so strange. air in our ears. As the pressure increases, the
balloon will bec
. A
balloon will bec
balloon will bec
. A
. A
balloon will bec
. A
ome smaller
ome smaller
t a depth of
t a depth of
t a depth of
t a depth of
ome smaller
ome smaller
When we stand on land at sea level, we are balloon will become smaller. At a depth of
as
as
e it w
e it w
10 m, the balloon will be half the siz
10 m, the balloon will be half the siz
standing in 1 atmosphere (atm) of pressure. 10 m, the balloon will be half the size it was
on the surface. At a depth of 20 m, where
This is the normal pressure of the air in the on the sur f ac e. A t a depth of 20 m, wher e
e is 2 atm higher than at the
the atmo
spher
atmosphere that we live in every day. the atmosphere is 2 atm higher than at the
surface, the balloon will be a third of its
When we go underwater, the pressure sur f ac e, the balloon will be a thir d of it s
increases because the water above us also original size.
creates pressure. The deeper you go, the
higher the pressure; for every 10 metres (m) Science in action
of depth, the pressure increases by another 1 Scuba divers have to understand how air changes under
atm. pressure because it lets them know how long they can stay
underwater. At great depths, the pressure is very high and it
compresses the air in their tank. In a way, this means that they
have ‘less’ air to breathe. So the deeper they go, the less time
they can stay there before they have no more air left.
D. Read again and complete
the diagram below.
pressure = atm balloon is full size
sea level
depth = m pressure = 2 atm balloon is
its original size
depth = 20 m pressure = atm balloon is a third
of its original size
E. Discuss the following.
If you ill a balloon with air on the surface
and take it down to 20 m, it will become
much smaller. If you take it back up to
the surface again, what do you think will
happen? Why?
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