Investigation

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Answers:

Investigation 10.1

3. What Happens to the limewater in flask D after some time? Explain your observation.
A white precipitate is formed. The snail gave off CO2 during respiration.

4. You need to set up a control. What would you put in Flask C?
Dead snails soaked in formalin to prevent decay.

5. If your investigation uses a potted green plant, what precaution must you take? Explain your answer.
The pot must be covered with a polythene bag to prevent carbon dioxide to enter from the soil. A black cloth is also need to cover the plant to prevent it from photosynthesizing.

Science Skills

What purpose does the potassium hydroxide solution serve?
It is needed to remove Carbon Dioxide.

What purpose does the limewater serve?
Its acts as an indicator for Carbon Dioxide.

Investigation 10.2

3. What do you observe after some time? Explain your answer.
The Limewater turned into a white precipitate.

Science Skills

Why do you need to boil the glucose solution before carrying out the experiment?
It is to remove dissolved oxygen and carbon dioxide from the glucose solution. Oxygen must be removed as fermentation is anaerobic respiration, which takes place in the absence of oxygen. Carbon Dioxide is removed as it will interfere with the results.

What does the layer of oil serve?
The layer of oil prevents oxygen and carbon dioxide from the air from entering the yeast suspension.

What would you add to the boiling tube in a control experiment?
Everything will remain the same except that boiled yeast solution will be used. The yeast suspension is boiled, cooled then used.

Investigation 10.3

3. Cotton wool helps to insulate the apparatus and support the seeds. What other purpose does it serve?
The cotton wool allows oxygen to diffuse in and carbon dioxide to diffuse out of the flask.

5. Note the readings in the thermometer after one or two days. What conclusions can you draw?
Reading in the thermometer of Flask A is higher than the reading in the thermometer in Flask B. Geminating seeds produce heat during respiration.

6. What are the advantages of inverting the flasks?
Firstly, fewer seeds are needed to be used. Secondly, the thermometer does not need to be inserted deeply and lastly, the reading in the thermometer is easier to read.

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