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Osmosis Lab with Eggs

Osmosis Lab with Eggs

 

Principles investigated: Passive Transport, Diffusion, and Osmosis

 

Standards:

CA- California K-12 Academic Content Standards

• Subject : Science

• Grade : Grades Nine Through Twelve
Standards that all students are expected to achieve in the course of their studies are unmarked. Standards that all students should have the opportunity to learn are marked with an asterisk (*).

• Area : Biology/Life Sciences

• Sub-Strand : Cell Biology

• Concept 1: The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism’s cells. As a basis for understanding this concept:

 Standard a: Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.

 

 

Materials:

Each group of 6 students will share:

  • 1 electronic scale
  • 1 ruler
  • 1 piece of string (20 cm)  
  • 2 eggs with hard shell removed
  • One 250 ml beaker with corn syrup
  • One 250 ml beaker with tap water

 

Objectives: 

  • Students will be able to distinguish between diffusion and osmosis
  • Students will be able to compare and contrast diffusion and osmosis
  • Students will be able to predict the movement of solutes or solvent during diffusion and osmosis
  • Students will be able to determine the tonicity of a solution around a cell based on the movement of the solvent during osmosis
  • Students will be able to predict the effects of a hyper, hypo, or isotonic solution on a cell or organism
  • Students will be able to discuss applications of diffusion and osmosis
  • Students will be able to relate diffusion and osmosis to physiological phenomena

 

Procedure:The teacher needs to prepare the eggs. The hard shell is removed by soaking the eggs into vinegar for two days. The calcium carbonate of the hard shell is dissolved by the acetic acid in the vinegar.

1st Part

1. Measure the circumference at the fattest part, and the mass of the two eggs. Record your measurements in the data table on your lab sheet.

2. Place one egg into the beaker with corn syrup, and the other egg into the beaker with tap water.

2nd Part - One hour later:

1. Remove the eggs from the corn syrup and water. Dry them by rolling them gently on a sheet of paper. Measure the circumference and the mass of the two eggs again. Record your measurements in the data table.

2. Place the eggs back to the corn syrup and water.

3rd Part (Optional) - 48 hours later:

1. Remove the eggs from the corn syrup and water. Dry them by rolling them gently on a sheet of paper. Measure the mass of the two eggs again. Record your measurements in the data table.

Safety: Wash hands with antibacterial soap after handling the eggs!

Student prior knowledge:

Students have basic knowledge about solutions and concentration. Students have basic knowledge of the structure of the cell membrane as related to its function.

 

Explanation:

The eggs behave like the cells. The egg represents the cell and the membrane around it represents the cell membrane. The egg placed into corn syrup shrinks because it releases water. The corn syrup is a very concentrated fructose solution. The sugar molecules cannot cross the membrane therefore the water moves out of the egg by osmosis. The egg placed into tap water grows because it absorbs water. In both cases the water moves across the membrane from the less concentrated solution to the more concentrated solution, which we call osmosis.

 

Applications of Passive Transport to Physiology:

·       gas exchanges between the respiratory and circulatory system and the circulatory system and the cells

·       absorption of nutrients from the digestive system

·       water balance

·       diseases of abnormal membrane permeability include cystic fibrosis.

·        

Applications of Passive Transport to Everyday phenomena:

·       air fresheners are based on diffusion

·       water filters are based on reverse osmosis

 

References:

http://www.lessonplansinc.com/lessonplans/osmosis_lab.pdf

 

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Norman Herr,
Dec 1, 2010, 10:33 PM
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