Dry Lab!

So to be honest, it's taken me like a week to figure out what in the world a dry lab is and how to even do it.  But now after time, I figured it out, I think!  So here goes nothing!

First of all you need to get four clean test tubes, a bottle of bromothymol blue, access to water, straws, snails, and elodea (plant).

Now take one clean test tube and fill it up halfway full with water.  Place 30 drops of the bromothymol blue into the test tube and get your straw.  No you're not going to drink it.  Take the straw and blow bubbles into the mixture in the test tube.  Record your observations.

Next, grab the second test tube also filling it halfway full with water.  Just like the previous step, place 30 drops of bromothymol blue into the water.  But, instead of blowing bubbles, place a snail into the test tube.  After 3-5 minutes record observations and remove the snail.

Then, take the third test tube, fill it halfway full with water and place 30 drops of bromothymol blue into the water in the test tube.   Now, insert one elodea (plant) into the test tube mixture.  Place it in an area with sunlight. After 3-5 minutes record your observations and remove the plant.

Finally, take the last tube and fill it halfway full of water, placing 30 drops of bromothymol blue into the test tube.  After that take one snail and one elodea into the test tube.  Take the test tube into a very dark area with no sunlight whatsoever!  After 3-5 minutes record your observations.  Don't forget to take the snail and elodea out after though! 

OBSERVATIONS AND EXPLANATIONS!
In step one the mixture begins as a blue color because of the bromothymol blue.  After blowing bubbles into the mixture, it turns to a light greenish yellow color.  This is caused from carbon dioxide being in the water which produces carbonic acid. 
In step two, the water will begin to turn a light color.  It changes to a light color because the snail is constantly respiring. 
In step three, the water turns a blue-green color.  The carbon dioxide and the water yield sugar and oxygen when chlorophyll and sunlight are around. 
In step four, the water will change into a yellow color.  This is because there is no sunlight which means the plant is unable to photosynthesize.  The plant is always creating carbon dioxide, along with the snail also in the tube.  The water turns acidic because of the abundant amount of CO2, causing the yellow coloring of the mixture.