Read Microsoft Word - 24_28OsmosisandDiffusionLab.doc text version

Name ____________________________________ Date _____________________ Partner ______________________________________ Role __________________ Part A Diffusion Purpose: In this lab, students can see firsthand the diffusion of a substance across a semipermeable membrane. Materials: · tincture of iodine · cornstarch/water solution · dialysis tubing · beakers Procedure: 1. Fill beaker about halfway and put about ten drops of iodine. 2. Put a teaspoon of starch and about 50 ml of water in dialysis bag and tie

Osmosis and Diffusion Lab

3. Put the baggie in the beaker and wait. After 10 minutes observe the baggie and the beaker. Note any changes in the data table below. Data: After 10 min. After 15 min. After 20 min. After 25 min. Changes observed

Discussion Questions: 1. The plastic bag is permeable to which substance? ___________________________ 2. Why did the iodine enter the bag? ______________________________________ __________________________________________________________________ 3. Why didn't the starch enter the beaker?_________________________________ __________________________________________________________________ 4. How is the plastic bag like the cell membrane? _____________________________ __________________________________________________________________

PART B: OSMOSIS In this investigation you will use a fresh egg to determine what happens in osmosis. You will be measuring the amount of water that passes through the membrane lining the shell of th3 egg. MATERIALS: fresh egg in shell wax pencil, 200 mL graduated cylinder 3 jars with covers white vinegar, clear sugar syrup (Karo, for example), distilled or bottled water. DAY 1 PROCEDURE: 1. With the wax pencil, label the three jars: vinegar, syrup, water. Also put the number of your group on each jar. 2. Using the graduated cylinder, measure out 200 mL of vinegar. Put it in the jar labeled "vinegar". 3. Place the egg in the jar. The vinegar should cover the egg. Cover the jar with the lid but do not screw it on tightly. 4. Put the jar in the plastic tray and allow it to stand for 24 hours. DAY 2 PROCEDURE: 5. Observe what has happened to your egg. Record in Figure 1 of the data sheet. 6. Using the graduated cylinder, measure 200 mL of syrup and pour it into the correct jar. 7. Carefully remove the egg from the vinegar. It is quite fragile now as the shell is dissolved. Very gently rinse the egg in water and place it in the syrup jar. Put the cover on loosely. 8. Using the graduated cylinder, measure the amount of vinegar left in the vinegar jar. (If any vinegar has overflowed into the tray, include it in the measurement.) Record the volume of remaining vinegar in Figure 1 on the data sheet. DAY 3 PROCEDURE: 9. Measure 200 mL of water and add it to the water jar. 10. Carefully remove the egg from the syrup jar. Record your observations of the egg's appearance in Figure 1 on the data sheet. 11. Place the egg in the water jar. Cover loosely. Allow to stand for 24 hours. 12. Measure the volume of liquid that remains in the syrup jar. (If any has spilled out,

include it in the measurement.) Day 4 PROCEDURE: 13. Remove the egg from the water and record your observations of its appearance. Discard the egg in the container provided. 14. Measure the amount of water that is left in the jar. Record in the data table. 15. Answer the questions on the data sheet. Data Table: Volume before egg was added Vinegar Syrup Water QUESTIONS: 1. When the egg was placed in the water, in which direction did the water molecules move? __________________________________________________________________ __________________________________________________________________ 2. On what evidence do you base this? __________________________________________________________________ __________________________________________________________________ 3. How do you explain the volume of liquid remaining when the egg was removed from the syrup? __________________________________________________________________ __________________________________________________________________ 4. When the egg was placed in the water after being removed from the syrup, in which direction did the water move? __________________________________________________________________ __________________________________________________________________ Volume after egg was added Observations of egg after 24 hours.

PART C: PLASMOLYSIS The purpose of this activity is to investigate the effects of a hypertonic solution on the cells of the red onion. MATERIALS (per student): red onion epidermis, forceps, dropper, distilled water, 5% Sodium Chloride (table salt) solution, paper towels, microscope, slide, cover slip PROCEDURE: 1. Make a wet mount of the red onion epidermis. 2. Examine under 100X. When you have a clear view of several cells, switch to 430X. Make a colored drawing, properly labeled in the first circle on the data sheet (Fig. 2). 3. Begin to drop some of the salt solution under one side of your cover slip while placing a small piece of paper towel along the opposite edge of the cover slip. The paper should draw out the water and draw in the salt solution. 4. Observe the effects of the solution on the onion cells. Make a properly labeled, colored drawing of the cells' appearance in the second circle on the data sheet (fig. 3). 5. Replace the sodium chloride solution with distilled water in the same way that the salt solution was added. Make a properly labeled, colored drawing of the cells' appearance in the third circle on the data sheet (Fig. 4). 6. Answer the questions on the data sheet. Figure 2 Figure 3 Figure 4

QUESTIONS: 1. Which of the two liquids was hypotonic? __________________________________________________________________ __________________________________________________________________ 2. On what evidence do you base this? __________________________________________________________________ __________________________________________________________________ 3. Which of the two liquids was hypertonic? __________________________________________________________________ __________________________________________________________________ 4. On what evidence do you base this? __________________________________________________________________ __________________________________________________________________ APPLICATIONS: Using concepts developed from the two experiments, Answer the questions of application. 1. Why do grocery store owners spray fresh fruits and vegetables with water? __________________________________________________________________ __________________________________________________________________ 2. Roads are sometimes salted to melt ice. What does this do to plants around the roadside and why? __________________________________________________________________ __________________________________________________________________ 3. If a shipwrecked crew drinks sea water, they will probably die. Why? __________________________________________________________________ __________________________________________________________________ 4. If a bowl of fresh strawberries is sprinkled with sugar, a few minutes later the berries will be covered with juice. Why? __________________________________________________________________ __________________________________________________________________

Information

Microsoft Word - 24_28OsmosisandDiffusionLab.doc

5 pages

Report File (DMCA)

Our content is added by our users. We aim to remove reported files within 1 working day. Please use this link to notify us:

Report this file as copyright or inappropriate

370855


You might also be interested in

BETA
Canning Fruits
Texture - A hydrocolloid recipe collection
Microsoft Word - hydrocolloid-recipe-collection-v2.1.doc