4.5. ALL THINGS MUST PASS
(Level: 8 : 11 acad : 11 appl :: Osmosis)

Purpose: To observe osmosis in an animal membrane.

What You Need:2 eggs :: distilled water :: vinegar :: concentrated salt solution :: 2 beakers :: spoon

Note: Dilute hydrochloric acid works more effectively than vinegar. Make sure that it is diluted at a ratio of 5:1 water:acid

WARNING: Always pour acid into water. Never pour water into acid. Wear goggles.

What You Do:

1. Dissolve the shells from the 2 eggs. Do this by placing them in a beaker of vinegar until they dissolve (time will vary from one to several hours).
2. Turn the eggs from time to time with a spoon. Tap them gently with a spoon to see if the shells are gone. Do not leave the eggs in the vinegar too long after the shells are gone, as some of the contents will be destroyed and the experiment will not work.
3. When the shells are gone, remove the eggs with a spoon. Gently rinse them with water. Handle them very carefully as the membranes may break.
4. Fill Beaker A with distilled water and place one egg in it.
5. Fill Beaker B with a concentrated salt solution and place the other egg in it.
6. Observe the eggs over a period of a few hours and record your observations.

Questions:

1. In what direction did most of the water move in Beaker A? How do you know?
2. In what direction did most of the water move in Beaker B? How do you know?
3. Does osmosis occur through this animal membrane? How do you know?
4. Why is osmosis important to all living things?
5. Where does osmosis occur in amphibians?

Click here to see the answers to these questions.
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