Gax exchange (plants) Pg31,32

Question 1

What is the reactant and product of gas exchange in plants

Answer 1

Reactant is oxygen, product is carbon dioxide

Question 2

Where does the waste product leave through in plants

Answer 2

stomata

Question 3

How do gases move to and from plants

Answer 3

diffusion

Question 4

During the day, plants use up more … than they release so they take in …

Answer 4

carbon dioxide

Question 5

During the day, plants make more … than they use in … so they release …

Answer 5

oxygen, respiration, oxygen

Question 6

What is the gas exchange in plants at night

Answer 6

They only respire as there is not enough light. They take in oxygen and release carbon dioxide

Question 7

How are leaves adapted for efficient gas exchange

Answer 7

• Leaves are broad so large surface area for diffusion
• A leaf is very thin so they have a short diffusion distance
• There are air spaces inside the leaf so they let gas diffuse through cells easily
• Lots of stomata, which means carbon dioxide and oxygen can diffuse in and out of leaf. They also allow for transpiration
• Stomata begins to close when it gets dark and as photosynthesis can’t happen, they don’t need to open to let carbon dioxide in.

Question 8

How do you test for gas exchange

Answer 8

• add the same volume of hydrogen-carbonate indicator to 4 boiling tubes
• Put similar-sized and healthy-looking leaves into the three tubes and seal with bung. Trap the leaf stem with the bung to stop the leaf from falling into the indicator. Keep the 4th tube as a control
• Completely wrap one tube with aluminium foil and a second tube with gauze and the third one with no cover
• Place all the tubes in bright light and leave for an hour
  RESULTS:
  1. The control colour should remain orange as no carbon dioxide produced
  2. The foil tube should be yellow as carbon dioxide produced by respiration taking place and no photosynthesis
  3. The gauze tube should remain orange as photosynthesis and respiration take place, no carbon dioxide is being released as it gets used again by photosynthesis
  4. The indicator turns purple as carbon dioxide concentrations decrease as photosynthesis gas exchange is greater than respiration’s so it will take in more carbon dioxide than it is releasing.

Question 9

What colour does hydrogen-carbonate indicator turn in different carbon dioxide concentrations

Answer 9

orange with normal carbon dioxide concentrations
yellow with higher carbon dioxide concentrations
purple with lower carbon dioxide concentrations

Question 10

What does hydrogen-carbonate indicator measure

Answer 10

change in carbon dioxide concentrations