Photosynthesis "Dry Lab"

DRY LAB

Usually in biology class we do experiments to come to a conclusion about something, but in this experiment I am going off of observations and facts. In the lab we are going to be using fish from an aquarium and a plant called elodea. We are concentrating on the affects of carbon dioxide on water mixed with water and bromothymol.



MATERIALS:

• 4 beakers
• water
• bromothymol blue (BTB)
• 2 elodea
• 2 aquarium fish

EXPERIMENT PROCEDURES:

• Step 1: Fill a beaker 3/4 full of water. Mix 40 drops of bromothymol blue. Place the beaker in light for 3 hours and then place it in the dark for 3 hours. Make observations through every step.
• Step 2: Fill another beaker 3/4 of the way with water and mix 40 drops of bomothymol. Place the beaker in light for 3 hours then in the dark for 3 hours.
• Step 3: Fill another beaker 3/4 of the way with water and add 40 drops of BTB. Place an elodea in the mixture. Place the beaker in light for 3 hours and in the dark for 3 hours.
• Step 4: Fill a beaker 3/4 full of water. Add 40 drops of BTB. Put an aquarium fish and an elodea in the mixture. Place the mixture in light for 3 hours and dark for 3 hours.

OBSERVATIONS:

1. When mixing BTB with water, it was a blue-green color. It stayed that color and did not show a change with the transition of the lighting.
2. When mixing BTB with water and an aquarium fish, it was a blue-green co9lor. It turned yellow but then didn't change with transition of the lighting.
3. When mixing BTB with water and an elodea, it turned blue the 3 hours it was in the light and it turned yellow when placed in the dark.
4. When mixing BTB with water, an aquarium fish, and an elodea, it turned a pale blue-green color for the 3 hours placed in the light and when placed in the dark, it turned yellow.

FACTS:

• Carbon dioxide in water produces carbonic acid.
• Carbon dioxide plus water yields sugar and oxygen when chlorophyll and sunlight are present.
• Green plants photosynthesis in the light and respire all the time.
• Sugar plus oxygen yields carbon dioxide plus water and energy.
• Animals respire
• Bromothymol blue (BTB) is a blue-green liquid which change3s to a yellow color in acid and back to blue-green when returned to a neutral pH.

Down below are some explanations about my observations above:

1. The solution was a blue-green color because that's the color of BTB and water is clear so when added to it, there was no color change.
2. The water changing yellow was caused by the BTB being mixed with water and added to an acid. When carbon dioxide is added to water, it produces carbonic acid. The fish breathing causes the carbon dioxide. When the carbonic is produced, the solution changes colors.
3. When plants are placed in the light, they absorb carbon dioxide and release oxygen. When an elodea in the solution and place it in the light, it will absorb the carbon dioxide in the solution. That's what makes it stay blue-green in the light, but in the dark, the plant doesn't absorb carbon dioxide which causes the solution to turn yellow.
4. When the aquarium fish and elodea are placed in the solution together under the light, the solution remains blue because the plant absorbs the carbon dioxide the fish breathes out, keeping it neutral. Remember when you put the solution with the fish and elodea in the dark, it turns yellow because the plant can n longer absorb the carbon dioxide.