Answer Happy

Question 3 A student set up three test tubes - A, B and C - to measure some of the gases produced by aquatic organisms. Each tube contained pond water and a CO₂ indicator. The student placed two water snails in tube A, a strand of pondweed in tube B, and a strand of pondweed and two water snails in tube C. The tubes were then capped with airtight stoppers and left in bright sunlight for 12 hours. The experimental setup is shown below. B After 12 hours, the concentration of dissolved carbon dioxide was determined using a colour change chart as shown in the following table. COLOUR OF INDICATOR Purple Red Yellow LEVEL OF CO2 IN THE WATER Low b. In which tube, A or C, would you expect the snails to live the longest? Explain. Medium High a. At the start of the experiment, the CO₂ indicator was red in all three test tubes. i. What colour would you expect the indicator to be after 12 hours in Tube A? Explain. ii. What colour would you expect the indicator to be after 12 hours in Tube B? Explain. iii. What colour would you expect the indicator to be after 12 hours in Tube C? Explain.