2010 Biology Paper 3 - Question 1(Continuation)

1(e(i) Construct a table and record all the data collected in the experiment. Your table should have the following titles:

• Type of activity
• Initial and final readings of the lengths of air column
• Percentage of carbon dioxide in the air sample

Type of activity	Initial readings of the lengths of air column (cm)	Final readings of the lengths of air column (cm)	Percentage of carbon dioxide in the air sample (%)
Resting 0 minute	10.0	9.9	1
1 minute running on the spot	10.0	9.8	2
2 minute running on the spot	10.0	9.7	3
3 minute running on the spot	10.0	9.6	4

(e) (ii) Use the graph paper provided on page 9 to answer this question. Using the data in l(e)(i), draw a line graph of the percentage of carbon dioxide against the time of activity.

Uniform scales on both axes : 1 mark

4 points plotted correctly : 1 mark

Join all 4 points correctly : 1 mark

f) Based on the line graph in l(e)(ii), explain the relationship between the time of activity and the percentage of carbon dioxide in the air sample.

When the time of activity increases, the percentage of CO2 released increases because more energy is required, so respiration takes place at a faster rate.

g) This experiment is repeated on the same student but the exhaled air is collected 10 minutes after each activity. Predict the percentage of carbon dioxide released. Explain your prediction.

1% //decrease because respiration went back to normal rate, ie same as resting. Less energy is produced/needed.

h) State the operational definition for exhaled air.

Exhaled air contains CO2/is the air column which is absorbed by potassium hydroxide in the J-tube. The length of air column is influenced by time of activity.

(i) The following list is part of the materials and apparatus used in this experiment.

Complete Table 4 based on the list given above.

Material	Apparatus
Exhaled air sample Water Potassium hydroxide solution	Beaker Boiling tube Rubber tube J-Tube