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photosynthesis lab help

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So the dreaded photosynthesis lab is upon me, and I think i know what i am doing. I just need your guys's wonderful insight and review on my idea. So i will be manipulating the light intensity levels to see how it will factor the photosynthesis rate in Amazon Sword Echinodorus amozonicus). I will use sodium bicarbonate as a carbon source and will keep a controlled amount of 5g of baking soda in the experiment. Then i would carry out the lab, having 5 trials on a specific light intensity, then another 5 trials on another light intensity, and so on until i can get in 25 trials (5 different light intensities). Then, to measure the rate of photosynthesis, i would measure the pH level of the water. If the rate of photosynthesis is high, then the pH would be lower, as the plant is absorbing more CO2 in the water. If the rate of photosynthesis is low, then the pH of the water would be high, as the plant would not be able to absorb much CO2. For qualitative data, i can use the strength of the baking soda in the water as a gauge, with a stronger smell meaning not much CO2 was absorbed, and vice versa. I can also explain the amount of bubbles, observing that many bubbles would lead to a high photosynthesis rate as well. Would this lab be good? The only thing i am worried about is i mght have enough time to carry out the entire lab. I only have a week to do this, and 50 min in a class period.

Also, if you could suggest some other ideas on a photosynthesis lab, that would be quite delightful!

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I did my Bio IA on photosynthesis....gahh.

haha :D

I would suggest maybe having a fewer amount of light intensities, or maybe different kinds of lighting?

Just to make sure that you have proper time to do all of your trials!

:) I really wish you good luck with your project!

:blowkiss:

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Sounds fine to me, although 5 trial re-runs is not entirely necessary. All of my internals were three trials and taking the average of the data, that way you can suggest repeated trials as a method of decreasing random error. So five light intensities and three trials.

If you are measuring the pH of the water as your dependent variable, another option if the experiment is not running according to plan is to resort to counting the bubbles of oxygen rising in the test tubes presumably. But this is only a back-up, measuring the pH is fine and more consistent and reliable if using a pH meter.

So with regards to your query about time, there is no need to do five trials, three is sufficient. This should reduce time significantly.

Edited by Hus

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oh i wish i could lower my trial numbers, but our teacher said it was a full out IA, which means a 5x5 lab. I assume 5x5 means 5 trials and 5 sets of trials. correct me if im wrong.

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Yeah that's fair enough, every teacher has their own set of protocols. It seems your teacher wants you to do 5 trials of each light intensity, best to follow their instruction.

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oh and could you give me any idea on how to keep the plant from floating during the experiment? i was thinking i could cut the plant to be small enough to fit into a test tube, but then it would not be exposed to the carbon-filled water in the beaker....so unless i can find a way to keep the plant from floating to the top, then i might have to use a test tube. or would a floating plant not matter in the experiment, and as long as the plant is in contact with the water, it will absorb the carbon dioxide?

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We used test tubes filled with the carbonated water, which was made using a standard solution and one of those large 250mL flask mixing things.

Cutting a small piece of the aquatic plant and placing it into the test tube tightly so it doesn't float. I think it would be better if the plant was in a fixed position if possible, so ensure the plant isn't too large or too small, rather tightly fit into the test tube.

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