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Experiment 7.5A: Gaseous exchange (氣體交換) of
Objective:
To study the gaseous
exchange of mealworms in bright and dark conditions.
Procedures:
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1.
Place the following set-ups in a bright place.
2. Measure the distance
(距離) between the stopper and
the red ink marker in
each capillary
tube
(毛細管). Take measurements
(量度) again after 5 minutes.
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Results:
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Set-up
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Distance between the stopper and
the red ink marker (cm)
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|
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Just after setting up
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After 5 minutes
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|
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A
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10.2
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1.1
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B
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11
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11.1
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Discussion:
(a) Explain the results in set-up A.
The mealworms
take in oxygen from
the air in the boiling tube and releases
carbon dioxide.
Soda lime absorbs (吸收) carbon dioxide from
the air in the boiling tube.
The total amount of the gas inside the boiling tube
decreases
(increases / decreases).
As a result, the red ink marker moves towards (towards / away from) the boiling tube.
(b) What is the use of set-up B?
There is no mealworm in
set-up B. If there is any change in
the position of its red ink marker,
it means there are changes in other factors, e.g. temperature and air
pressure. These factors
will also
(not / also) affect set-up A.
By comparing the results in set-ups A
and B, we can know the actual effect
(真正影響) brought
about by the
mealworms
in set-up A.
Set-up B
is known as the control
experiment for set-up A.
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(c) Study the design of
set-up C as shown below.
What condition does set-up
C simulate (模擬), compared with set-up A?
Set-up C simulates the condition at night (in the daytime / at
night) while
set-up A simulates the condition in the daytime.
Design a control experiment (對照實驗) for set-up C. Draw a labelled
diagram to show it and call it set-up
D below.
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The following table shows the results of set-up A and B.
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Set-up
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Distance between the stopper and
the red ink marker (cm)
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Just after setting up
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After 5 minutes
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|
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A
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9
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2
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C
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8
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1
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(c) Explain the results in set-up C.
The mealworms
takes in oxygen from the air in the boiling tube and releases
carbon dioxide which is absorbed by soda lime.
The total amount of the gas inside the boiling tube
decreases.
As a result, the red ink marker moves towards the boiling tube.
(d) What is the use of set-up D?
There is no mealworm in
set-up D. If there is any change in
the position of its red ink marker, it means there are changes in other
factors, e.g. temperature and air pressure. These factors
will also affect set-up C.
By comparing the results in set-ups C
and D, we can know the actual effect brought about by the
mealworms
in set-up C.
Set-up D is known as the control
experiment
for set-up C.
Conclusion:
Ø
The mealworm takes in oxygen and releases carbon dioxide in both bright and dark conditions.
Ø
The gaseous exchange of the mealworm is the same in
both bright and dark conditions.
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