ALEX Lesson Plan

This lesson plan includes several hands-on, inquiry-based lab activities exploring the concepts of osmosis and diffusion. The lesson plan is divided into three modules. First, the teacher will demonstrate osmosis and diffusion using gummy bears, salt, celery, food coloring, and hot and cold water. Next, students will participate in a hands-on lab activity that will demonstrate diffusion using various concentrations of corn starch and Lugol’s solution. Lastly, students will demonstrate the process of osmosis using dialysis tubing, sucrose solution, cornstarch, phenolphthalein, ammonia, vinegar, and universal indicator solution.

Student Materials (per student)

Pencil or pen

Notebook paper

Gloves

Safety goggles

Pre-/Post-Test – Osmosis and Diffusion

Student Instructions for Lab Part A Diffusion

Student Handout 1 Diffusion (to be used for data tables and analysis during lab)

Student Handout 2 Diffusion (to be used for reflection after completion of lab)

Student Instructions for Lab Part B Osmosis

Student Handout 1 Osmosis (to be used for data tables and analysis during lab)

Student Handout 2 Osmosis(to be used for reflection after completion of lab)

Student Materials (per group)

For Lab Part A-Diffusion

1 Plastic bag with 1 teaspoon of cornstarch

1 Plastic cup

1 bottle of Lugol’s Solution (iodine)

1 graduated cylinder

Water (150 ml/per group)

For Lab Part B-Osmosis

1 plastic cup

1 8-inch pre-cut and soaked dialysis tubing

1 graduated cylinder

4 8-inch pre-cut pieces of dental floss

Scales

Water

Additional Group Materials Needed For Lab Part B-Osmosis

Groups 1 and 2 need:

20% sucrose solution

Bottle of red food coloring

Groups 3 and 4 need:

Bottle of Phenolphthalein

Household Ammonia

Groups 5 and 6 need:

Bottle of vinegar

Bottle of Universal Indicator Solution

Groups 7 and 8 need:

Distilled water

40% sucrose solution

Bottle of red food coloring

Teacher Materials

Teacher Preparation and Procedures

Pre- and Post-Test Osmosis and Diffusion ANSWER KEY

Osmosis and Diffusion Presentation

For Day 1 Teacher Demonstration:

9 plastic cups

Gummy bears

Package of red Kool-Aid

30% salt solution

3 celery stalks

Hot and cold water

Interactive whiteboard/projector with ability to project computer

Student Background Information: As this lesson will introduce students to the processes and effects of diffusion and osmosis, students do not need to possess background knowledge about these concepts prior to participating in the lesson’s activities. This lesson will require students to participate in hands-on, inquiry-based lab activities. The students will need to be able to follow multi-step procedural instructions in order to complete the experiments. Students will be participating in lab activities in which chemicals will be handled. Students should follow all appropriate safety precautions including wearing gloves and goggles. All spills and splashes should be cleaned with water.  

Teacher Background Information: The teacher should preview the Teacher Preparation and Procedures prior to teaching the lesson to ensure that the teacher demonstration and student lab activities are prepared for students prior to beginning the lesson’s activities. In addition, this preparation packet includes the expected outcomes of the experiments included in this lesson. As written, the activities included in this lesson will require at least four class days to complete. The teacher can view the Osmosis and Diffusion Presentation for additional background information about the concepts taught in this lesson. The teacher should review lab safety precautions with students and ensure students follow these procedures for the duration of the lesson.

The teacher will need to complete the following preparations for the teacher demonstration one day prior to beginning the lesson:

1. Soak gummy bears (one color per cup) overnight in water.

2. Add 150 grams of salt to 500ml of HOT water and mix to dissolve as much as possible.

3. Soak celery stalks in salt water overnight.

4. Soak another celery stalk in tap water overnight.

The teacher will need to complete the following preparations for the Lab Part B Osmosis one to two days prior to students beginning this portion of the lesson:

1.  Cut dialysis tubing into 8-inch sections. Each group will need 1 piece.

2.  One or two days before the lab, soak the dialysis tubing in distilled water, tubing should be covered with water.

3.  Cut four 8 inch pieces of dental floss for each group: for 8 groups, 32 pieces are needed.

4.  To prepare 20% sucrose solution:

Place 20 grams of sugar in 100ml of distilled water.

To prepare 40% sucrose solution place 40 grams of sugar place in 100ml of distilled water (if this does not dissolve readily, heat the water to hasten the process).

5.  Prior to beginning lab, place the following at each lab station:

1 piece of dialysis tubing in distilled water; 1 plastic cup; 1 graduated cylinder; Four 8 inch pieces of dental floss; 1 pair of gloves for each student

6.  At a central location, place scales and tap water.

7.  At another central location, have the additional materials needed for each group.

8.  Have each group label their plastic cup with their group number.

9.  Have a designated place for each group to leave their dialysis tubing in a plastic cup overnight.

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.

Formative: The teacher will informally assess student’s background knowledge by administering the Pre-/Post-Test – Osmosis and Diffusion prior to teaching the lesson. The teacher should carefully monitor students as they complete the lab activities with their groups to certify that students are correctly following the lab procedures. The teacher should review each student’s Student Handout 1 Diffusion and Student Handout 1 Osmosis ensure that students are collecting accurate data.

Summative: The teacher will formally assess students at the conclusion of each lab experiment by reviewing each student’s Student Handout 2 Diffusion and Student Handout 2 Osmosis. The teacher will administer the Pre-/Post-Test – Osmosis and Diffusion as a summative assessment at the end of the lesson.

Students can further explore the concepts taught during this lesson by completing Student Handout 3-Critical Thinking independently or with their collaborative group.

Students who require additional preparation prior to the lesson or review after the lesson can view the Osmosis and Diffusion Presentation which succinctly summarizes the concepts demonstrated during this lesson’s lab activities.