Photosynthesis: Experiment Instructions (Lab Report)<=”” span=””>Note: These experiments were adapted from two different web sites. Links are provided to them so that you can look at their wonderful pictures and illustrations that make the process more clear. However, you need to follow the instructions here to do the experiment correctly. MATERIALS NEEDED (Oxygen Production)Lamp Compact Fluorescent Light (curly light bulb) of at least 60W equivalence (13W or better) Fresh Spinach Leaves Straw or single hole puncher
Liquid Soap or Liquid Dishwashing Soap (for handwashing dishes, not machine washing detergent) Plastic Syringe with NO NEEDLE! (ask a pharmacist for the measuring syringe to give a child liquid, oral medicine) Baking Soda Clear Glass or Cup Timer Colored Plastic Wrap or Tissue Paper Box or Cover to block light Semi-dark Room <=”” span=””>MATERIALS NEEDED (Chromatography of Plant Pigments)Tall, Clear Glass Fresh Spinach Leaves and one other type of leaf that Isn’t Green (Fall leaves work well, but they must not be dry) Pencil Rubbing Alcohol (from the first aid section of your pharmacy) White Coffee Filters
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Penny or Nickel Ruler<=”” span=””>Don’t forget to fill out the Experiment Tracking Sheet for each section of the exercise. Remember to take one picture of Floating Leaves and one picture of Chromatography for the lab report. PHOTOSYNTHESISYou will be cutting out circles of spinach leaf and watching them float to show oxygen production during photosynthesis. After cutting out the circles of leaf, you will place them inside a plastic syringe and pull back on the plunger to create a vacuum and suck out the air from inside the leaves. The leaf circles will now sink. After 10-20 inutes in bright light, the leaf circles will have produced enough oxygen to inflate and float like tiny rafts. You will use different colors of paper or plastic to see which colors work well for photosynthesis. You will also be crushing leaf pigments onto a coffee filter (paper is polar) and then drawing rubbing alcohol (mostly non-polar) up the filter to see which pigments move up with the alcohol and which stay still. You will measure the distance each pigment moves and compare it to the total distance the alcohol moved. Experiment #1 – Oxygen Production (http://www. elbiology. om/labtools/Leafdisk. html) 1. (Identify Control Variables) Add 1/2 tablespoon of baking soda to 4 cups of water. (When baking soda dissolves, it releases CO2 into the water. ) Add a small drop of liquid soap to the water and stir to mix. If you see a large number of bubbles, start over and use less soap. <=”” span=””><=”” span=””><=”” span=””> 2. Using the end of a straw or single hole punch, cut out 15-20 circles of spinach leaf. 3. Pull the plunger completely out of the syringe and put the leaf circles into the syringe. Push the plunger back in.
Use the syringe to suck up the baking soda water until the syringe is about 1/4 or 1/3 full of liquid. 4. Place your finger over the end of the syringe and pull back on the plunger as far as you can without pulling the plunger out. This should create a vacuum. (If leaf circles stick to the sides of the syringe up in the air space, swirl the solution so that they fall down into the solution. ) 5. Repeat step #4 three times. All leaf circles should now sink to the bottom of the liquid. (If some are still floating, repeat step #4 again and make sure the circles are all submerged in liquid. ) 6.
Place the spinach circles into a clear glass with about 2 inches of baking soda solution. Immediately cover to block out all light. 7. (Positive Control Experiment) Set up the lamp with a compact fluorescent light bulb in a semi-dark room. (No sunlight, low levels of other light. Bathrooms work best for this usually. ) When you are ready to begin, place the glass in front of the lamp. Count the number of circles that are floating after each minute for 20 minutes. This is your positive control experiment. Notice the bubbles coming out of the floating circles. 8. (Negative Control Experiment) <=”” span=””>Are you sure the ircles don’t just float on their own after 20 minutes? Create a negative control experiment to confirm that this is a really a reaction between both components. Use fresh spinach circles to do this experiment. 9. (Hypothesis) Repeat the experiment with fresh circles, but use regular water for all steps instead of baking soda water. Regular water has very little CO2 in it. <=”” span=””> Make a hypothesis about how lack of CO2 should aftect the rate at which circles float. 10. (Hypothesis) Choose three different colors of plastic wrap or tissue paper, including clear or white.
Consult the absorbance graph in the pre-lab material to make a hypothesis about how passing the light through each of these colors (turning it into that color) should affect the rate at which the circles float (speed of photosynthesis). 11. Wrap the glass with one of these colors and repeat the experiment with fresh spinach circles. (Move the glass closer to the lamp if the plastic or paper blocks a large amount of the light. If no circles float when using white tissue paper, get a thinner paper or increase the time to 1 hour and measure every 3 minutes. ) Repeat for all colors.
Conclusions – Did the plant produce oxygen and float as expected? Which colors of light didn’t cause the circles to float? Make a line graph showing the results each minute. <=”” span=””> Experiment #2 – Chromatography of Plant Pigments(http://k12videos. mit. edu/content/time-for-me-to-leaf-tree-chlorophyll-chromatography)<=”” span=””>Note: Please watch the video above first. It is hard to visualize this experiment from just words, but the video makes everything clear. 1. Get a few spinach leaves and one or two other leaves of different colors or shades of green from around your house. Medium to large leaves work best.
Leaves should not be tough or dry. Red and yellow fall leaves work well, and it is particularly interesting if you can get a two different colored leaves from the same plant. 2. <=”” span=””>(Identify Control Variables) Cut coffee filter into two or three strips 1 inch wide. Make strips approximately the same length. 3. Mark each strip 1 1/2 inches from the bottom with a PENCIL. (Ink separates during chromatography, so only use pencil markings. ) Lay down several paper towels to work on. Lay one spinach leaf over (or under) the coffee filter strip. Roll a penny or nickel across the leaf (or across the