Paper 3 Question 2

SBP Trial 2010 Paper 3 Question 2 -to consider:

Transpiration is the loss of water vapour from plants, especially in leaves. Transpiration occurs mostly through the stomata. The amount of water lost by a plant depends on its size,surrounding light intensity, temperature, humidity and wind speed.

Diagram 3 shows the movement of water in a terrestrial plant.

Based on the information, design an experiment to be conducted in the laboratory to investigate the effect of the number of leaves on the rate of transpiration in a hibiscus plant.

The planning of your experiment must include the following aspects:

_ Objective of investigation

_ Hypothesis

_ Variables

_ List of materials and apparatus

_ Technique used

_ Experimental procedures

_ Presentation of data

_ Conclusion [17 marks]

TIPS:

***IDENTIFY THE VARIABLES

Aim : To investigate the effect of the number of leaves on the rate of transpiration in a hibiscus plant.

Problem Statement: HOW does the number of leaves affect the rate of transpiration (in hibiscus plants)?

Hypothesis:

The more the number of leaves the higher rate of transpiration. OR

When the number of leaves increases the rate of transpiration increases.

VARIABLES:

Manipulated variable: Number of leaves / stomata

Responding variable: Distance travelled by air bubble (in five minutes)// The rate of transpiration

Controlled variable: Type of (terrestrial) plant / hibiscus // Light intensity //Surrounding temperature

Materials & Apparatus:

Materials: *Hibiscus shoot / plant, water, and plasticine.

Apparatus: *Ruler / weighing balance, capillary tube + rubber tubing // potometer //

stoppered conical flask, beaker / basin, (sharp) knife, stopwatch, string /

marker pen and tissue paper / filter paper.

Technique:

Recording the distance travelled by air bubble in five minutes using a stopwatch.

OR

Calculating and record the rate of transpiration by the formula:

Rate of transpiration = Distance travelled by air bubble/Time

Procedure:

Able to state five procedures P1, P2, P3, P4 and P5 correctly.

P1 : How to Set Up The Apparatus (5P1)

P2 : How to Make Constant The Control Variable (1P2)

P3 : How to Manipulate The Manipulated Variable (1P3)

P4: How to Record The Responding Variable (2P4)

P5 : Precaution / Accuracy (2P5)

PROCEDURE:

1. (Diagram of experimental setup with at least 5 functional labels). P1

2. Obtain a hibiscus shoot and immediately immerse in water. P1/ P5

3. By using a sharp knife, cut off 4 cm of the hibiscus stem under water. P5

4. Fill in the capillary tube with attached rubber tubing / potometer with water. P1

5. Fix in the stem of the hibiscus shoot into the rubber tubing / potometer.Make sure no air bubble trapped. P1/ P5

6. Immerse the capillary tube / potometer in a beaker of water. P1

7. Wipe dry the leaves with tissue papers. P5

8. Leave the setup for 5 minutes (for the plant to adapt with the new environment). P5

9. Lift the capillary tube from the water to trap a column of air bubble // Trap an air

bubble in the capillary tube / potometer. P1

10. Tie a string on the capillary tube to mark the initial position of the air bubble. P1

11. Start the stopwatch. P1

12. After 5 minutes tie another string to mark the final position of the air bubble. P1

13. Repeat step 12 to get another reading. P5

14. Measure both distances by using a ruler. P4

15.Calculate the average distance traveled by the air bubble in 5 minute. P4

16.Record in a table // Tabulate the data. P4

17. By using the same plant,repeat steps 7 until 13 by removing one leave each time.P2/ P3

18. Calculate the rate of transpiration. P4

Result:

Conclusion : Rewrite hypothesis sentence.