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Leaf Disk Lab DIRECTIONS SHEETBasic Materials needed for lab group of 3-4 students:-Spinach leaves?-straws-Large Syringe-.2 % sodium bicarbonate (baking soda) solution-Test tube/small beakers/plastic cup-Light sourcePurpose of Experiment:We are using leaf disks as a measure of the rate of photosynthesis. The leaf disks will be submerged in a baking soda solution that will act as a source of carbon dioxide for photosynthesis. As the disks create oxygen through photosynthesis, oxygen bubbles will accumulate on the leaf and it will begin to float. The number of disks that float within a given time frame can be used as a measure of the rate of photosynthesis. Variables can be changed and the effect on photosynthesis can be assessed by comparing the number of disks that float within the time frame of the experiment.Preparation of the leaf disks:1) Use the end of a straw to cut out the number of disks needed for your experiment. Use 10 disks per experimental condition. You will have two conditions so that is a total of 20 disks. Cut out 25 to be safe. Please be efficient with the spinach leaves so that we have enough for everyone!2) Put all 25 disks in a syringe and suck up a small amount of the diluted soap water. Expel any air, but avoid crushing the disks. 3) Put finger over end of syringe, pull back on plunger to create a vacuum, and hold this position for 10 seconds. You might see bubbles forming as air is sucked out of the spongy part of the leaf. You may need to tap the syringe to make sure all disks stay submerged. 4) Carefully squirt out the soapy water. Suck up some more soapy water as in step 2. Check to see if the plant disks sink in the water. If they don't, repeat step 3. You may need to do this 2-3 times for all the disks to sink.Directions continued on Back 5) Get 2 beakers and fill them with soap-water Put 10 leaf disks in one beaker and 10 disks in the otherThe disks should sink to the bottomAdd 3 pinches of baking soda to each beaker6) Put one beaker under one type of light, and the second beaker under a different type of light7) Fill out the grid on the back of your paper with your dataNAME__________________________________LEAF DISK LAB1) Where does the oxygen produced during photosynthesis come from?2) What factors might affect the rate of photosynthesis in the leaf disks? Name at least 3 factors. We will come together as a class to come up with experiment ideas for day 2.3) Do you think the leaf disks will be able to make oxygen bubbles and float if there is no bicarbonate solution to provide a source of CO2? Why or why not? 4) Based on our discussion today, you will choose a variable to test tomorrow. Your independent variable (what you will be manipulating) is: The dependent variable (what you will be measuring/counting) is: 5) Your hypothesis is: 6) Explain the logic of the stated hypothesis:Data chart: Condition 1 ______________________Condition 2 _________________________MinutesCondition 1# floating disksCondition 2# floating disks0123456789101112131415Graph of data (use a piece of notebook paper, make appropriate graph that has a title and is properly labeled, attach graph to this lab report) ................
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