Before Strategy/Engage: 50 minutes (Day 1)
1. The teacher should give each student a copy of the Pre-/Post-Test – Osmosis and Diffusion. The teacher should give students approximately ten to fifteen minutes to complete the pre-test. The teacher should stress to students that the purpose of the pre-test is to demonstrate the student’s background knowledge about the concepts of osmosis and diffusion.
2. After students complete the pretest, the teacher should check students’ answers to determine their current knowledge base of the concepts using the Pre-/Post-Test – Osmosis and Diffusion Answer Key. Alternatively, the teacher could allow students to check their own paper or check a partner’s paper.
3. Next, the teacher will demonstrate osmosis and diffusion using gummy bears, salt, celery, food coloring, and hot and cold water.
Teacher Demonstration
a. Show students dry gummy bears and a cup of water. Ask students to write their prediction of what will happen if the gummy bears are soaked overnight in the water.
b. Show students a cup of salt water and a stalk of celery. Ask students to write their prediction of what will happen if the celery soaks overnight in salt water.
c. Show students a package of Kool-Aid and a cup of hot water and a cup of cold water. Ask students to write their prediction of what will happen to the Kool-Aid when added to the cup of hot water and the cup of cold water.
Next, the teacher should display demonstration set up the previous day:
a. Gummy bears soaked in water
b. Celery in salt water and celery in tap water
c. The effect of adding one teaspoon of Kool-Aid into hot water and one teaspoon of Kool-Aid into cold water
4. The teacher should allow students to discuss how closely their predictions matched the actual demonstration. The teacher should ask student volunteers to predict why the materials in the experiment were affected by the hot and cold water and the salt water.
During Strategy/Explore & Explain: 100 minutes
Lab Part A-Diffusion-50 Minutes (Day 2)
For the next portion of the lesson, the students should be divided into collaborative groups of approximately four students each. The teacher should give each student a copy of Student Instructions for Lab Part A Diffusion. The students should follow the directions on the Student Instructions for Lab Part A Diffusion.
1. Add 150ml of water to the plastic bag containing corn starch. Remove as much air as possible and seal the bag. Mix by moving contents of the bag back and forth gently to dissolve corn starch.
2. Groups 1 and 2 add 10 drops of Lugol’s solution and 250ml of water to a plastic cup; Groups 3 and 4 add 20 drops of Lugol’s solution and 250ml of water to a plastic cup; Groups 5 and 6 add 30 drops of Lugol’s solution and 250ml of water to a plastic cup; Groups 7 and 8 add 40 drops of Lugol’s solution and 250ml of water to a plastic cup.
3. BE SURE YOUR PLASTIC BAG IS COMPLETELY SEALED. Record the starting colors on Student Handout 1 Diffusion, Table A. Then place the SEALED bag containing the cornstarch solution into the plastic cup containing Lugol’s solution so that the contents of the bag are completely covered by the solution.
4. After 10 minutes, observe any changes in color and record your data in Student Handout 1 Diffusion, Table A; after 30 minutes observe any changes in color and record your data in Student Handout 1 Diffusion, Table A. Leave your bag in the plastic cup overnight. Make your final observation of colors the next day and record your data in Student Handout 1 Diffusion, Table A.
5. Answer Data Analysis Questions 1 – 5 on Student Handout 1 Diffusion, Part A.
6. Answer Conclusion Questions 1 – 7 on Student Handout 2 Diffusion, Part A.
7. Answer Elaborate Questions 1 – 5 on Student Handout 2 Diffusion, Part A.
Lab Part B-Diffusion-50 Minutes (Day 3)
For the next portion of the lesson, the students should be divided into eight different collaborative groups. The teacher should give each student a copy of Student Instructions for Lab Part B Osmosis. The students should follow the directions on the Student Instructions for Lab Part B Osmosis.
1. All groups: Moisten your fingers to open the dialysis tubing. Tie a knot at one end of the tubing approximately 1 inch from the end (knot 1) using dental floss; approximately 1 inch above the knot tie another knot (knot 2) using dental floss. TIE ALL KNOTS TIGHTLY. MAKE SURE YOU HAVE SECURE KNOTS (NO LEAKAGE). Keep the dialysis tube moist but avoid getting water inside the tube.
2. Groups 1 & 2: Fill the dialysis tube 1/3 full with 20% Sucrose solution.
Groups 3 & 4: Fill the dialysis tube 1/3 full with phenolphthalein (~40 drops)
Groups 5 & 6: Fill the dialysis tube 1/3 full with Universal Indicator (~40 drops)
Groups 7 & 8: Fill the dialysis tube 1/3 full with distilled water (~40 drops). Add one drop of red food coloring to the dialysis tube.
3. ALL Groups: Approximately 1 inch from the open end of the tubing tie one knot using dental floss and using the same CAREFUL technique used in Step 1 (Knot 1). Approximately 1 inch below Knot 1, tie the tubing again (Knot 2).
4. All Groups: Carefully rinse off the outside of the tube to remove anything that may have spilled on it. Gently pat it dry with a paper towel.
STEP NUMBER 5 MUST BE COMPLETED BEFORE YOU PROCEED ANY FURTHER!
5. All Groups: Using the scales, find the mass of the filled dialysis tube. Record this information on Student Handout 1 – Osmosis on Data Table A.
Groups 1 & 2: Put 100 ml of water in a plastic cup. Add one drop of red food coloring to the water.
Groups 3 & 4: Put 75 ml of water in a plastic cup. Add 25 ml of ammonia to the water.
Groups 5 & 6: Put 75 ml of water in a plastic cup. Add 25 ml of vinegar to the water.
Groups 7 & 8: Put 100 ml of 40% sucrose solution in a plastic cup.
6. ALL Groups: Place your dialysis tube in the plastic cup with the solution you made. Make sure it is fully covered. Observe and record the beginning color and your results after 15 minutes or until color change on Student Handout 1 Osmosis, Data Table B.
Leave the dialysis tubing in the plastic cup overnight.
THE NEXT DAY:
7. Observe and record the overnight results in Student Handout 1 Osmosis, Data Table B.
8. ALL Groups: Remove the dialysis tube, gently pat it dry and find the mass using the scales. Record this data Student Handout 1 Osmosis, Data Table A.
9. ALL Groups: Compare your data with the other groups that tested different substances. Record the results from the other groups in the correct Tables A and B.
10. Students should work with group members to answer discussion question on Student Handout 2 Osmosis.
After Strategy/Explain & Elaborate: 50 minutes
1. After all groups have completed the lab activities on diffusion and osmosis, the teacher should lead a class discussion among all of the groups to compare each group’s data.
Note: If the teacher identifies that students need additional review before the summative assessment, the teacher may show students the following presentation to review the concepts demonstrated during the lab activities: Osmosis and Diffusion Presentation.
2. The teacher should give the students the Pre-/Post-Test – Osmosis and Diffusion, the same test that students completed as a pre-test at the beginning of the lesson. The teacher should explain to students that this post-test will allow students to demonstrate the knowledge they acquired during the lab activities.
