Hobbies And Interests
Plant Osmosis With Celery
Osmosis in plants causes their cells to expand. Do an experiment to show the effect water and the lack of water have on plants and the importance of osmosis to them. Cut the bottoms of two celery stalks, with leaves, using scissors to make sure each can absorb liquid. Place one in a clear glass half full with dark blue water. Place the other stalk in an empty clear glass. Leave both overnight to observe the next day. It's a good idea to take pictures of what the stalks look like initially so you see an accurate change. The stalk in water is upright and rigid and has blue-tinged leaves. This shows how osmosis carries water through plant cells. The stalk in the empty glass is wilted because the turgor pressure, the force that keeps plant cells rigid, has decreased with the lack of water.
Osmosis in Potatoes
This experiment shows how osmosis works by placing potatoes in different water solutions. Each potato is lengthwise. For child safety, an adult should do this. Fill one dish with saltwater and one with freshwater. Then place one sliced potato, flat side down, on each dish. After a two-hour wait, check the potatoes for differences. The potato in the freshwater has changed little, though usually slightly more rigid. This shows the part of osmosis where water flows into a space, in this case the potato, with more solute (salt). The other potato slice, in the saltwater, looks wilted and is soft and flexible. This shows how water is pulled, out of the potato, to where there is more solute.
Egg Osmosis
An egg is a good object for representing a cell because it has a membrane. Document the weight of several raw eggs before placing them in a jar of vinegar for two days. The process can make the vinegar start to resemble beer. After the two days are up, carefully rinse the eggs under the tap. The shells should have dissolved. The membrane around the eggs will be intact. The eggs will also have increased in size. This shows osmosis because the water in the vinegar moves towards the lower concentration of water in the egg. If you place the eggs in corn syrup, the opposite effect will happen. The eggs shrink because the corn syrup has less water than the egg.
Carrots and Salt
Use carrots as another example of plant osmosis. Fill two clear glasses halfway with warm water. Dissolve salt in one glass and cut or snap a carrot in two. Tie a string to each carrot piece and then place one in the freshwater and one in the saltwater, cut or snapped ends down. Leave them overnight. The next day, pull each one out. The one in saltwater shrinks because the water moved out of the comparatively lower solute concentrated carrot and the one in freshwater bloats because in this case the carrot has a higher solute concentration than the water around it.