Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Lab experiments

  1. Aug 19, 2004 #1
    these are lab experiments in which i have gathered but i still haven't performed them... can anyone please determine the basic answers or give tips for the upcoming experiments? :approve: thanks very much~

    Making Salted Eggs/ Pickled Eggs
    I. Objective:
    To illustrate osmosis/diffusion in making salted eggs/pickled eggs.

    II. Materials:
    1 kettle
    1 plastic bag
    2 big, clean glass jar
    3 cups salt
    1 liter water
    1 dozen fresh eggs
    a piece of string
    red pepper
    III. Procedure:
    A. Salted Eggs:
    1. Prepare the brine solution by boiling enough water and constantly adding salt until saturation point is reached. This is determined when salt no longer dissolves in water.
    2. Allow the brine solution to cool. Pack the eggs in wide-mouthed glass jars or any suitable container.
    3. Pour the cold brine solution over the eggs. Put a small plate on top of the eggs to prevent the eggs from floating when pouring water.
    4. Cover the mouth of the jar with clean cheesecloth.
    5. Keep in cool, dry place. After 12 days, boil an egg and taste it. If the egg is not salty enough, keep the eggs in the solution of one more week. Boil. The salted eggs are now ready to be ready.
    B. Pickled Eggs:
    1. Hard-boil the eggs in a sauce pan (about ten minutes for chicken eggs).
    2. Cool the eggs immediately under running water.
    3. While waiting for the eggs to cool, prepare the pickling solution. Add sugar to vinegar (1:1). Put in salt, black pepper, red pepper, and garlic to taste. Simmer for ten minutes.
    4. Shell the eggs and pack carefully in glass jars or any suitable container.
    5. Pour the hot pickling solution into the jar. The solution should be just enough to cover the eggs. Remove the black pepper.
    6. Seal tightly and air-cool. After a week the pickled eggs will be ready.

    V. Observations and Questions:
    1. What enables the salt particles to pass through the membrane and into the egg?
    2. Why did water particles move out from the egg?
    3. What process caused the saltiness of the egg?
    4. What property of matter enabled the salt to penetrate through, thus making the egg salty?
    Separation of Leaf Pigments
    I. Objective:
    To separate cell substances from the leaves and from each other.

    II. Materials:
    spinach leaves
    developing solution (8% acetone 92% petroleum ether)
    several strips of filter or chromatography paper
    fine sand
    test tube, 25x200 mm
    cork to fit test tube
    pipette, with a very fine tip
    mortar and pestle
    test tube rack
    cheesecloth 10X10 cm2
    glass making crayon
    cleansing tissue
    2 pencils
    paper clip

    III. Procedure:
    Caution: Because ether is being used, at no time should there be an open flame in the room.
    1. Using the larger test tube, assemble the apparatus as shown in the figure. But do not yet add the developing solution and pigment.
    2. Handle the paper carefully with the forceps. Even a small amount of oil from your fingers will affect the results.
    3. Adjust the paper in the tube so it does not touch the sides or bottom. Mark on the test tube the level of the lower end of the notch.
    4. Remove the paper strip from the hook. Then pour developing solution in the test tube to a depth of 5 mm below the mark that you made.
    5. Place the cork with the hook attached (but without the strip of paper) in the test tube. Place the tube in an upright position in a rack. Support the strip of paper across two pencils so that it does not touch the table.
    6. Put four of five San Francisco leaves, a little sand, and 10 ml of acetone into a mortar. Grind thoroughly. The acetone now contains extracted pigments.
    7. Place a layer of cheesecloth in a funnel. Add a layer of cleansing tissue.
    8. Pour acetone into the funnel. Collect the filtrate in the smaller test tube.
    9. Using a fine-pointed pipette, place a drop of the pigment extract on the paper between the notches. Allow to dry. Add another drop in the same place, and allow to dry. Repeat until you have placed at least four drops in the paper- one to top of another.
    10. When the final drop was dried, remove the cork from the large test tube and hang the strip on the hook.
    11. Insert the cork with the paper strip attached into the test tube. Do not allow the pigment spot to touch the developing solution. Adjust the length of the hook to avoid this. Be sure the cork is tight.
    12. Watch the developing solution rise. When it almost reaches the hook, remove the cork from the tube. Take the paper off the hook, with the forceps and recork the tube. Hold the paper until it dires.
    13. Examine the chromatogram.

    IV. Questions and Answers:

    (Refer to procedure No. 8 in answering questions No. 1 and 2).
    1. What is the color of the filtrate?
    2. Is there any evidence that more than one pigment is dissolved in the acetone?
    Refer to procedure No. 13 in answering questions 3-8.
    3. How many bands of color can you see in the chromatogram?
    4. How many bands might be made up of chlorophyll?
    5. What other colors can you see in the chromatogram?
    6. Why were you unable to see these colors in the leaf?
    7. Do you think that all of the leaf pigments were soluble in the acetone? Why or why not?
    8. Suggest a hypothesis to explain the change of color that often occurs when a leaf dies.
    Refer to procedure No. 12 in answering questions 9-11.
    9. From what point did all the pigments start as the developing solution began to rise?
    10. When did all the pigments start to move, and when did they all stop?
    11. In what characteristic then, must the pigments have differed?
  2. jcsd
  3. Aug 19, 2004 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I think you should first do the experiments, listen to what your teacher teaches about the subject related to each experiment, then if you still have questions, come back and ask about the specific things you need some help understanding. Otherwise, we're just going to spoil all your fun of waiting to see the results for yourself!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook