Osmosis is the movement of water through membranes by diffusion. Scientists first observed and studied osmosis in the 1700s, but it is today a basic scientific concept learned at school. Through this phenomenon, animals, plants and other living beings can keep their cells hydrated. Simple experiments using potatoes can help children to understand the concept of osmosis and its importance for cell maintenance and survival.
Cut four potato slices, dry them with a paper towel and weigh them. Prepare four solutions of different concentrations using black-currant or other concentrated fruit drink and water. Place one potato slice in each solution; leave for at least 15 minutes. Remove the potato slices from the solutions, dry with a paper towel and weigh them again. Compare the weights of potato slices from different solutions. Also observe the relation between the concentration of the solution and the firmness of the potato slices.
Salt and Sugar Solutions
Prepare two concentrated solutions. Add 2 tbsp. salt to a cup of water and the same quantity of sugar in another cup of water. Cut three potato cylinders or slices. Weigh and measure them. Put one potato slice in the salt solution and other in the sugar solution. The third potato slice put in a cup with water. After 24 hours, remove the potato slices and dry, weigh and measure them. Compare results and write down a hypothesis to explain them.
Salt Solutions of Different Concentrations
Use two soup plates to prepare two salt solutions. Fill the plates with water. Add 1 tbsp. salt to one plate and 1 tsp. salt to the other. Cut two slices from a potato and place one in each plate. Leave them for about two to three hours. Remove the potato slices from the water and try to bend them. Compare the results.
Effects of Temperature
Observe the effect of osmosis in potato cells in solutions with different temperatures. Prepare two identical solutions with a cup of water and 2 tbsp. salt. Heat one of the solutions in the microwave for about 30 to 45 seconds, until it is warm. Cut out two slices from a potato and place each one of them in one solution. Leave for 10 minutes, take them out and compare the results.
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