How would I measure the amount of oxygen given off during photosynthesis?

Question

Equipment needed and method please.

Answer 1

The best analytical setup would not measure the grams of Oxygen released, but the change in composition of the atmospheric gases.

The problem is that Carbon dioxide is consumed as well as the Oxygen released, so a simple mass measurement will not do.

The setup is very easy and in expensive. The analysis of the gas would be complicated. Access to a college chemistry laboratory or commercial chemistry lab would be required.

I suggest that algae be used for the plant because it grows fast is is very responsive to sunlight, but theoretically this method could work with any plant.

A large clear Mylar bag is used for the environment barrier. The plant is placed inside and the bag sealed. A syringe should be used to remove several samples of the initial air composition. This is repeated both during and immediately after periods of very bright light and sustained darkness.

The gas samples can be analyzed by Gas Chromatography or CG-Mass spec.

Answer 2

Here's a crude method which doesn't require any commercial or collegiate "lab" and may give decent results.

SETUP:
First, you need at least 6 giant Zip-Lock bags. (the kind that would could a basketball.) Four small candles (tea-light candles should do) and two seperate 4" boxes of alfalfa grass already growing. You will also need two small zip-lock bags and a pitcher of water. You will also need a stopwatch. Lastly, you need access to an Oxygen source (like a grandparent's oxy tank, or similar.


Read all of this experiment before trying any of it...that'r rule #1. Have a fire extinguisher handy...that's rule #2.

To get started, we need to know how long a candle burns given a certain amount of oxygen.
STEP 1, Fill a large zip-lock with air, put a candle in it, light it, seal it, and use the stopwatch to measure how long the candle stays lit. (You may use a bean bag to rest the whole thing on while waiting.....use tongs to hold the bag as it deflates and gets hot. Now you know how long a candle stays lit in a fixed amound of regular air.

Step 2, fill a small bag with oxygen from the source and release it into one of the large bags already filled with room air. (Be sure to do all of this with the zip-lock side face down.) Once you add a fixed quantity of oxygen into the large bag, light a new candle, seal it inside, and use the stopwatch to measure the time the new candle stays lit (just like step 1.

The difference in the two times is how long a candle would stay lit with just the small bag's worth of oxygen. I will call this result "A". (Do NOT try to verify this by putting a lit candle into a small bag of pure oxygen...trust me.)

Step 3, we have to quickly measure how much oxygen a bag holds.....I'd say fill a small bag with room tempurature water. Since the bag holds only slight pressure (not like a balloon) then the volume of water (in milliliters) is roughly the same as the volume of oxygen.

Dividing the result of Step 3 [volume] by the result "A" [time]should give you a "candle burn rate in oxygen enriched air."

The measurement should look like: 650-milliliters of oxygen burned in 42 seconds. or 15.5ml/sec (oxygen per second.)

All of the above steps were performed in order to "calibrate" our setup so we can use it for measuring the photosynthesis.

Finally...Put each alfalfa cube into a large bag add enough room air to puff out the bag as in step 1, then seal both bags.

Wait one week.

Open each bag and perform this test to measure the amount of oxygen. Take out the alfalfa and quickly put in a burning candle, then seal the bag. Use the stopwatch to measure the total time until the candle burns out. record this time on the same paper you've been recording times on.

Subtract the time from Step 1 which was just room air. The result is the number of seconds-worth of oxygen produced. Use your burn rate to convert this number of seconds into milliliters of oxygen produced. (example: 4 extra seconds of burn = 15.5 X 4 = 62milliliters of oxygen.)

Repeat with the second bag with alfalfa...record it's time...perform the same calculations.

What are all the possible things that could be different between one bag and the other? These are your sources of error.

Hope this helps.

Answer 3

1) imerse a water plant in a beaker of water
2) connect this to a gas syringe
3) place a lamp next to the apparatus
4) measure the volume of gas produced over time

Answer 4

It is hardly inposible but if you have some specil tools you might. It is hard work. I'm saying that you neep specil tools ask scintest this question I'm not one but it is easy to say though.