Osmosis Lab with Eggs
Principles investigated: Passive Transport, Diffusion, and Osmosis
Each group of 6 students will share:
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.
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.
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