F2 IS 2nd Term EXP Answers

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F2 IS EXP 06 Answers

1st Term EXP 06 Submission date：_____________ Name：______________________ Class & no.：2 _________(     )

Experiment 7.5A: Gaseous exchange (氣體交換) of

grasshopper (草蜢) mealworms (麥皮蟲) (P.48-50)

Objective: To study the gaseous exchange of mealworms in bright and dark conditions.

Procedures:

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.

Results:

Set-up	Distance between the stopper and the red ink marker (cm)
	Just after setting up	After 5 minutes
A	10.2	1.1
B	11	11.1

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.

(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.

The following table shows the results of set-up A and B.

Set-up	Distance between the stopper and the red ink marker (cm)
	Just after setting up	After 5 minutes
A	9	2
C	8	1

(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.

F2 IS EXP 05 Answers

1st Term EXP 05 Submission date：_____________ Name：______________________ Class & no.：2 _________(     )

Experiment 7.4A:

The iodine test (碘液試驗) for starch (澱粉)

Objective: To test for starch using iodine solution (碘液)

Procedures:

1.   Add a drop of starch solution (澱粉溶液) and a drop of water side by side onto a white tile (瓷磚).

2.   Add a drop of iodine solution to each of them. Observe the colours of the mixture.

Results:

Liquid	Colour after adding iodine solution
Starch solution	Dark blue
water	Brown

Conclusion:

Ø   Iodine solution can be used to test for starch.

Ø   A colour change from brown to dark blue shows the presence of starch.

Experiment 7.4X: To study the necessary conditions (必須條件) for photosynthesis to take place

Objective: To study the necessary conditions (light光 and chlorophyll葉綠素) for photosynthesis to take place

Design of Experiment:

To test whether light and chlorophyll are necessary for photosynthesis to take place, a variegated leaf (斑葉) covered with aluminium foil (鋁箔) is used as shown below:

  

Consider of “3Cs” of a fair test (公平測試)

n   Variable to be changed: The presence of chlorophyll and light

n   Variable(s) to be kept constant保持不變: (Put a “Ö” in the appropriate boxes.)

	The presence of chlorophyll or not	Ö	The supply of carbon dioxide or not
	The supply of light or not	Ö	Type of plant / leaf
Ö	Temperature	Ö	The supply of water or not

n   What to compare: The presence of starch

Procedures:

Preparation of the covered variegated leaf

1.      Destarch (脫澱粉) a potted plant with variegated leaves (斑葉) by putting it in the dark for 1 or 2 days.*
2.   Cover some part of a leaf with aluminium foil. Then, put the plant under bright light for several hours.*
3. Remove the leaf from the plant.

Test for starch in the covered variegated leaf

4. (a) Boil half a beaker of water. (b) Remove the covered variegated leaf from the potted plant. (c) Put the leaf in the boiling water for about two minutes. (d) Turn off the Bunsen burner.	Caution 1. Alcohol is flammable (易燃的). DO NOT heat it directly over the Bunsen flame! 2. Ensure that the Bunsen burner has been turned off.
5. (a) Half-fill a boiling tube with alcohol (酒精).   (b) Using a glass rod, transfer the leaf to the boiling tube. (c) Put the boiling tube into the beaker of hot water for about 10 minutes.
6.  (a) Take the leaf out of the alcohol. Observe what happens to the colours of the leaf and the alcohol.       The leaf becomes pale green and the       alcohol becomes green in colour.
(b) Put the leaf in the beaker of hot water for half a minute. Observe what happens to the leaf.       The leaf becomes soft.
7.  Carefully spread the leaf on a white tile. Add a few drops of iodine solution to it. Observe what happens.

*No need to be done by the students.

Results:

Draw a labelled diagram to show the result of the iodine test on the leaf.

The colours of different parts of the leaf after the iodine test:

	Green part	Non-green part
Part without cover	Dark blue	Brown
Covered part	Brown	Brown

Discussion: (P.30)

Starch is found in the green parts where chlorophyll is present / absent, but not in the non-green parts

where chlorophyll is absent. Therefore, chlorophyll is necessary for photosynthesis to take place.

The part of the leaf without cover (i.e. exposed to light) is dark blue, but the covered part

is brown. This shows that starch is found in the part exposed to light but not in the part not exposed to light.

What is the purpose (目的) of each step below? Write the letters representing the purposes on the blanks below.

Step		Purpose
1.   Put the leaf in boiling water.	(c)	(a) To test for the presence of starch in the leaf.
2.   Put the leaf in hot alcohol.	(d)	(b) To wash away the alcohol and to soften軟化 the leaf.
3.   Put the leaf in hot water again.	(b)	(c) To kill the leaf cells so that iodine solution can enter the cells later on.
4.   Add iodine solution to the leaf.	(a)	(d) To remove the chlorophyll (葉綠素)  to make the leaf lighter in colour for easy observation of the results of the iodine test.

Conclusion: (P.30)

Light and chlorophyll are necessary for photosynthesis to take place.