Peel a layer of skin from an onion. Place a drop of water on a slide and place the onion tissue in the water. Add another drop of water and a drop of iodine over the onion and cover with a glass slip. Examine under a microscope. Add 5 grams of salt to 100 milliliters of water. Place few drops of the solution to one side of the microscope slide. It will mix with the fluid on the onion. Observe the differences in the tissue. Repeat with 10 grams of salt mixed with the same amount of water on a new slide. The salt causes the protoplasm in the cell to shrink in a process called plasmolysis, creating clear differences in the slides.

find the Independent variable, The dependent variable and the control variable
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