Beacon Lesson Plan Library

What Is an Egg Without its Shell?

Wendi Henderson
Bay District Schools

Description

This lab activity allows students to observe osmosis – a cellular process that normally can't be observed without a microscope. Students follow the steps of the scientific method to observe osmosis in a chicken egg.

Objectives

The student understands the process of osmosis and diffusion.

Materials

For each lab group the following items are needed:
-[Science Voyages], 2000, Glencoe/McGraw-Hill, Columbus, OH (or any other science text with information on osmosis).
-Egg
-One 500 ml container with lid (a beaker covered with plastic wrap also works)
-White vinegar
-Graduated cylinder
-Spoon
-Paper towels
-Copies of Observing Osmosis activity sheet in associated file
-Liquids for students to choose from for day 3

Preparations

1. If the teacher is not familiar with cells and cell processes (osmosis & diffusion), refer to science sources to become more knowledgeable in this area.
*Note: This activity should follow students' understanding of diffusion. Since osmosis is the diffusion of molecules through a semipermeable membrane, students need to understand the concept of diffusion before tackling osmosis!
2. Gather materials for the activity.
3. Provide liquids for students to choose from for day 3 (i.e.: corn syrup, pancake syrup, salt water, sugar water, etc.)
4. Make copies of the activity sheet for students.
5. Make copies of the rubric for teacher and student use.
6. Prepare extra eggs in vinegar in case a group’s egg breaks after osmosis occurs.
7. The bubbles that collect on the eggshell after 30 min. are caused by the reaction between the calcium carbonate in the shell and the acetic acid in the vinegar

Procedures

1. Ask students, “What is the largest single cell on Earth?” (Answer: an ostrich egg). If available, show a picture of an ostrich egg (or the real thing!)

2. Hold up a chicken egg. There will be students who do not believe the egg is a single cell. Compare the characteristics of the egg (a single cell) as opposed to a fertilized egg (more than 1 cell). Ask students to identify the cell membrane (just beneath the shell) and the nucleus (the yolk).

3. Challenge students to devise a way to remove the eggshell without disturbing the cell membrane. (It may help students to know the shell is made of calcium carbonate).

4. Distribute the lab activity sheet, “Observing Osmosis” (see attachment). Students should work in groups of 2-4 students. Review your expected cooperative worker rules with students. Review the steps of the scientific method with students before beginning the experiment. You may need to write these on the board or point them out on the sheet. This will depend on how much your students have worked with these steps.

5. Read the problem: How does osmosis occur in an egg cell?

6. Discuss the process of osmosis.

7. Students formulate a hypothesis and record on the activity sheet.

8. After reviewing safety rules, cooperative group expectations, and experiment procedures, students may begin the activity as explained in “Observing Osmosis” activity sheet. The teacher should visit each group during the activity to check for understanding and cooperative effort.

9. Upon completing the lab procedures #1-#7 on the activity sheet, hold a class discussion comparing groups' results of the experiment, reviewing what happened, & analyzing how osmosis occurred.

10. Formatively assess students as explained below and on the assessment attachment.

Assessments

In groups of 2-4, students design and perform an experiment demonstrating reverse osmosis. The teacher will circulate from group to group to formatively assess students working cooperatively.

Students should follow the steps of the scientific method (state the problem, formulate a hypothesis, develop experiment procedures, make observations/record data, & make a conclusion) to model the process of osmosis.

Upon completion of this activity, the 3 analysis questions are used to formatively assess students' knowledge of osmosis.

This is assessed formatively using a rubric (see attachment).

*Though diffusion and osmosis go hand-in-hand, this activity presents and assesses osmosis primarily.

Attached Files

The attached document is the activity sheet, assessment, and rubric.     File Extension: pdf

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