Photosynthesis:

Experiment Instructions (Lab Report)

LEARiNING GOALS

By the end of this unit. you should be able to do the follow ing:

1. List the reactants and products of pliotosyniliesis.

2. Explain how diffei‘ent pi_•inents absorb and reflect differeni colors of lieht.

3. Explain lion’ each step of the floating leaf experiment relates to the reactants or products of pliotosynihesis.

4. Explain how ilie cliroinatograpliy experiineni uses polar paper and iioiipolar solseiit io separaie different pigiiieiits based on polarité.

5. Identify the Independeiii. Dependeiit, and Control Variables in your experinieiit.

Note: These experiments were adapted from Evo different          eb sites. Links are provided to tlieiti so ihat vou can look ai their z ondertiil pictures and illustrations that make the process more cleai’. Ho ever, you neeil to follow the instructions here to do the experiment coixectly.

âIATERI.TLS NEEDED (Oxygen Proiluction)

Lamp with bright LED bulb or C’oNipact Fluorescent (the cui’ly bulb). the brighter’ the better! Fresh Spinach Leaves

Straw or sinele hole punched

Liquid Soap or Liquid Disliwasliing Soap (for liandwasliiiie dishes, not machine washings

detergeiii)

Plastic Syring•e      iili NO NEEDLE! (ask a pliarinacisi for the measui’iiig syringe to give a child liquid. oral medicine)

Bakiiie Soda

Clear Glass or Cup

Tiiliei’

Box or Cover to block light

MATERIALS NEEDED (Chromatography of Plant Pigments)

Tall. Clear Glass

Fresh Spinach Leaves and one other type of leaf(Fall leaves work well. but they must not be dry)

Pencil

Rubbing Alcohol or Spray hand sanitizer or nail polish remover White Coffee Filters (#4 conical works best. but any works) Nickel

Ruler

Don’t 5orpef fo fill out the Expvriweut Trackiiig .Slieef for eacli svctioii o{tlie exercise. Remewber to take oiie picture o{Floating Leai'es and one pictura o{ Flirowatoqrapliy for the lab report.

PHOTOSYNTHESIS

You will be cutting out circles of spinach leaf and watching them float to show oxygen production diiring photosynthesis. Aiter 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 iliinutes in bright light, the leaf circles will have produced enough oxygen to inflate and float like tiny rails. You will use different colors of food coloring 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 Proiluction

(1ittos://www.youtube.con/watch?           8baZO89oc)

Note: Please watch the video above first. It is hard to visualize this experiment from just words. but the video makes everything clear.

1. 1. (I8enti     Control 1'ariables} Add 1/2 tablespoon of baking soda to 4 cups of

water. (When baking soda dissolves, it releases CO› 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.

1. 2. Using the end of a straw or sinele 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 syi                      ge 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 C’ontrol Experiment) Set up the lamp with a compact fluorescent light bulb. 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 posiiive control experiment. Notice the bubbles coming out of the floating circles.
   8. (Negative Control Experiment) Are you sure the circles don’t just float on their own after 20 minutes? Create a negaiive control experiment to confirm that this is a really a reaction between both components.

Use fresh spinach circles to do this experiment. You must have a negative control experiment in your report!

1. 9. (Hypothesis) Repeat the experiment with fresh circles, but use regular water plus soap for all steps instead of baking soda and soap water. Regular water has very little COC in it. Make a hypothesis about how lack of CO, should affect the rate at which circles float.

Conclusions - Did the plant produce oxygen and float as expected? Make a line graph showing the results each minute. The graph should have 3 total lines; 2 for the control experilTients and 1 for lack of CO2.

Experiment #2 - Chromatography of Plant Pigments

(hitps://www.youtube.com/watch?v= v6 5Zxdb68)

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. (lilentify Control X'al’iables) Cut coffee filters into four strips 1 inch wide. Make strips approximately the same length.
3. Mark each strip 3/4 inch from the bottom with a PENCIL. (Ink separates during clooniatography, so only use pencil iliarkings.) Lay one spinach leaf over the coffee filter strip. Roll a nickel across the leaf ONCE at the pencil mark. Press down as you are doing this to crush the leaf but don’t scrub!!!

Set the filter aside for 1 minute to dry. (This is critical. If the filter gets too wet, the leaf pigments will spread out and you won't get a clear line.) Repeat step #3 at least 15 times to get a dark, colored line at the bottom of the filter.

4. Do this process for each leaf type to be tested, using a different filter paper for each leaf.
5. Tape the top each filter paper to a pencil or pen. (The top is farthest from the leaf line; use one filter per pencil/pen.) Using an empty glass as a guide, roll the filter paper up on