1. Snail and Elodea Lab

2. Bromothymol blue Bromothymol blue (BTB) is a pH indicator
It is normally blue but turns yellow when the pH lowers
Carbon dioxide has a pH of 5.7
When carbon dioxide is present the color will change from blue to yellow
Oxygen has a pH of 6.7
When oxygen is present there will be no color change

3. Set up

4. Set up Tube 1= water + BTB Tube 2= water + snail + BTB
Tube 3= water + elodea + BTB
Tube 4= water +snail + elodea + BTB

5. Set up REMEMBER! Plants do BOTH photosynthesis and respiration Oxygen
Carbon dioxide
Carbon dioxide
Photosynthesis- Carbon dioxide + water + light  glucose + oxygen
Respiration- Glucose + oxygen  carbon dioxide + water + ATP
REMEMBER! Plants do BOTH photosynthesis and respiration

6. Interpreting Color Change
Blue no change or oxygen present
Yellow carbon dioxide present
Green carbon dioxide + oxygen present
Photosynthesis- Carbon dioxide + water + light  glucose + oxygen
Respiration- Glucose + oxygen  carbon dioxide + water + ATP

7. Set up Tube 1= water + BTB Tube 2= water + snail + BTB
Tube 3= water + elodea + BTB
Tube 4= water +snail + elodea + BTB

9. Explanation Tube #1= blue, no CO2 present Tube #2= yellow, CO2 present
Tube #3= blue, no CO2 present, plant making oxygen
Tube #4= green, CO2 and oxygen present