Osmosis Practical Investigation
Ever wondered why chips go soggy when you add salt? This osmosis experiment reveals the science behind water movement in cells. You'll use potato cylinders to see how different concentrations affect water flow.
Setting up your experiment is straightforward but precision matters. Use a cork borer to cut 8 identical potato cylinders, then trim them to exactly the same length with a scalpel and ruler. Weigh each cylinder on a top pan balance and record the starting mass carefully.
Your independent variable (what you change) is the solute concentration of your solutions. The dependent variable (what you measure) is the change in potato mass. Keep your control variables constant - temperature, surface area, volume of solution, and timing all stay the same.
Place each cylinder in a different concentration of sugar or salt solution (10cm³ in labelled boiling tubes). After a set time, remove them, blot dry, and weigh again to calculate mass change.
Key insight: The mass change tells you which direction water moved - into or out of the potato cells!
Understanding your results becomes simple once you grasp the basic principle. When the solution has a higher concentration than the potato's cytoplasm, water moves out and the cylinder loses mass. When it's lower concentration, water moves in and mass increases. If there's no change, the concentrations are equal and water moves both ways at the same rate.