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The following experiment was set up to investigate how a pondweed breathes in
the light and in the dark.
Note: The carbon dioxide indicator is a
coloured liquid which does not harm the plant. It can have three colours:
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Purple or violet =
No carbon dioxide
Red = A little carbon
dioxide
Yellow = A lot of
carbon dioxide |
At the beginning of the experiment the
carbon dioxide indicator was red. All three tubes were left in the light for a
few hours. Then the colour of the indicator liquid was recorded.
| 1. Why
was the aluminium foil wrapped around tube B? |
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| 2. Why
were the tubes filled to the top with liquid and stoppered with rubber
bungs? |
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| 3. Tube
C had no plant in it, just indicator liquid. Why was it important to
include this tube in the experiment? |
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| 4. Colour
the tubes in the diagram opposite in the colours you think they should
have after a few hours.
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| 5. What
does this experiment tell you about the way green plants, such as the
pondweed, exchange gases in the light and in the dark? |
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