7 WDYT? What do you think? What is going on in each container? Why are we putting 4 containers in the dark and 4 in the light?Why bromothymol blue?What does this do?Why should we have a control?
8 Initial Observation What color is the water? Will there be a change in what the liquid looks like after a couple of hours?What gas exchange is occurring?
9 Get into your groupsDiscuss your initial observationsDesignate a speaker to talk about your group’s initial observations
10 Info that may change your mind… Carbon dioxide dissolves in (and reacts with) water, forming carbonic acid, H2CO3CO2(g) + H2O(l) ←→ H2CO3 ←→ H+(aq) + HCO3–(aq)The free hydrogen ions (H+) lower the pH of the solution, making it more acidic.As CO2 dissolves in water, the pH of the solution will continue to decrease (becoming acidic). If CO2 is removed from the solution, the pH will increase (becoming more basic)
11 Bromothymol blueA pH indicator such as BTB can therefore indicate the relative amount of CO2 dissolved in water based on the color of the solution.Higher pH: Blue, basicLower pH: Yellow, acidic
12 Photosynthesis is Occurring 6CO2 + 12H2O 𝐿𝑖𝑔ℎ𝑡 C6H12O6 + 6H2O + 6O2Plant exposed to lightRemoves CO2 form the solutionRaises the pH (more basic)
13 Cellular Respiration is Occurring C6H12O6 + 6H2O + 6O2⎯⎯⎯→ 6CO2 + 12H2O + energySnail respires with or without lightDo plants have mitochondria? Can they respire? Look at Bottle 5.
14 Do plants have mitochondria? Can they respire? Look at Bottle 5. Yellow Indicating acidic solutionCO2(g) + H2O(l) ←→ H2CO3 ←→ H+(aq) + HCO3–(aq)Where did the CO2 come from?
15 Where did the CO2 come from in Bottle 5? The CO2 was produced as a result of cellular respiration by the plant.Both cellular respiration and photosynthesis occur in green plants when light is available.In Bottle 1, photosynthesis is the dominant process over respiration, resulting in a net decrease in CO2HOWEVER, in the absence of light, the plant cannot photosynthesize; it can only respireTHEREFORE, there is a net increase in CO2 concentration and the pH drops as the CO2 dissolves, producing carbonic acid.