Photosynthesis Dry Lab
In this “dry lab” you will be working backwards from what you would normally do in a lab situation. In this case, you will be given a set of observations that were made in a lab and you will be asked to reconstruct the procedure that could have generated this data. You will also be given a set of facts that you will use to explain this set of observations in the analysis and conclusions section of your lab write-up. As you create the procedure for this lab, please remember all the rules that you have been learning about good experimental design.
Your lab report begins below. Fill in the missing sections of the lab report using the observations and facts given. You may assume that you have access to as many test tubes, snails, Elodea plants, light sources, dark places, and as much pond water and BTB as you need.
Make your own copy of this Google Doc and edit the lab report that begins here:
My (only) Most Awesomest Photosynthesis Lab Report
by Cynthia Justice
Purpose: Is photosynthesis possible in animals? With different chemicals? Is light necessary?
Background Facts:
- Carbon dioxide in water produces carbonic acid.
- Bromothymol Blue (BTB) is a blue-green liquid which changes to a yellow color in acid and back to blue-green when returned to a neutral pH.
- Carbon dioxide plus water yields sugar and oxygen when chlorophyll and sunlight are present.
- Animals respire.
- Green plants photosynthesize in the light and respire all the time.
- Sugar plus oxygen yields carbon dioxide plus water and energy.
Hypothesis:
If I mix bromothymol with other ingredients in different conditions, the mixture will change colors.
Materials:
4 beakers
bromothymol blue
2 aquarium fish
2 elodea
waterProcedure:
1. Fill a beaker 3/4 full of water and mix with 40 drops of bromothymol blue (BTB). Leave in light for approx. 3 hrs. Then leave in dark for 3 hours. Observe!
2. Fill a beaker 3/4 full of water and mix with 40 drops of BTB. Put an aquarium fish in with the mixture. Put in light for 3 hrs. Put in dark for 3 hrs. Make observations.
3. Fill a beaker 3/4 full of water and mix with 40 drops of BTB. Add an elodea to the mixture. Leave in light for 3 hrs. Then in dark for 3 hrs. Make observations.
4. Fill a beaker 3/4 full of water and mix with 40 drops of BTB. Put both an aquarium fish and an elodea in the mixture. Put in light for 3 hrs. Put in dark for 3 hrs. Make those final observations!
Observations:
- Water plus bromothymol blue is blue-green.
- Water plus bromothymol blue plus an aquarium snail turns yellow.
- Water plus bromothymol blue plus Elodea (an aquarium plant) is blue-green in light.
- Water plus bromothymol blue plus a snail plus Elodea is blue-green in light and yellow when left in the dark for three hours.
Analysis and Conclusions:
- Water plus bromothymol blue is blue-green because...
- Water plus bromothymol blue plus an aquarium snail turns yellow because...
- Water plus bromothymol blue plus Elodea (an aquarium plant) is blue-green in light because...
- Water plus bromothymol blue plus a snail plus Elodea is blue-green in light and yellow when left in the dark for three hours...
the snail produces carbon dioxide, but there is no light, so the elodea can't go through photosynthesis and the carbon dioxide makes the water acidic, which creates the chemicals reaction and changes the water color in the dark.
