Osmosis

• What is osmosis?

  The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• What happens to a plant cell when it is placed in water?

  Water moves into the cell by osmosis, causing it to expand
• What occurs when a plant cell is placed in a concentrated solution?

  Water moves out of the plant cell by osmosis, causing the cell to shrink
• What type of vegetable is commonly used to investigate osmosis?

  Potato
• Why do we peel the potato before the experiment?

  Because the potato skin can affect osmosis
• What tool is used to produce cylinders of potato?

  A cork borer
• What is the recommended length for the potato cylinders?

  Approximately three centimeters
• Why is it important to have cylinders of the same diameter?

  To ensure consistent results in the experiment
• What should be measured for each potato cylinder before the experiment?

  The length and mass of each cylinder
• What solutions are added to the test tubes in the experiment?

  0.5 molar sugar solution, 2.5 molar sugar solution, and distilled water
• Why is distilled water used instead of tap water?

  Because distilled water contains no dissolved substances that could affect osmosis
• How long should the potato cylinders be left in the solutions?

  Overnight
• What should be done to the potato cylinders after removing them from the solutions?

  Gently roll them on a paper towel to remove surface moisture
• What is the formula to calculate percentage change?

  Percentage change = (change in value / original value) × 100
• If a potato cylinder has a starting mass of 1.56 grams and increases by 0.25 grams, what is the percentage change?

  +16.03%
• If a potato cylinder has a starting mass of 1.32 grams and decreases by 0.19 grams, what is the percentage change?

  • 14.39%
• What does the graph of percentage changes in mass or length against the concentration of the sugar solution show?

  In water, the potato cylinder gains mass; in concentrated sugar solution, it loses mass
• What does it mean when the graph crosses the x-axis?

  There is no change in mass, indicating equal concentration inside and outside the cell
• What is the approximate concentration inside the potato cell?

  The concentration where the graph crosses the x-axis
• What are the steps to investigate the effect of osmosis on plant tissue?

  1. Peel the potato to avoid skin effects.
  2. Use a cork borer to create uniform cylinders.
  3. Trim cylinders to approximately 3 cm.
  4. Measure length and mass of each cylinder.
  5. Place cylinders in test tubes with different sugar solutions.
  6. Leave overnight for osmosis to occur.
  7. Remove and roll on paper towel to remove surface moisture.
  8. Measure length and mass again.
  9. Calculate percentage change in length and mass.
• What are the effects of osmosis on potato cylinders in different solutions?

  • In distilled water: Potato gains mass (water enters).
  • In concentrated sugar solution: Potato loses mass (water exits).
  • At equilibrium: No change in mass (equal concentration inside and outside).