Required Practical 3: Effects of Osmosis on Plant Tissue

• What is osmosis?

  Diffusion of water through a membrane
• What happens to plant cells when placed in water?

  Water moves into the cell, causing expansion
• What occurs when plant cells are placed in a concentrated solution?

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

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

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

  Cork board
• What is the ideal length for potato cylinders?

  About three centimeters
• Why is it important to measure the length and mass of each cylinder?

  To assess the effect of osmosis
• How much of a 0.5 molar sugar solution is added to the first test tube?

  10 centimeters cubed
• Why do we use distilled water instead of tap water?

  Distilled water has no dissolved substances
• What should be done to the potato cylinders after soaking overnight?

  Gently roll them on paper towel
• 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 percent
• 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 percent
• What does the graph of percentage changes in mass or length against sugar solution concentration show?

  Mass changes with osmosis direction
• What does it mean when the graph crosses the x-axis?

  No change in mass occurs
• What concentration indicates no overall osmosis takes place?

  Concentration inside the cell
• What are the steps to investigate osmosis in plant tissue?

  1. Peel the potato.
  2. Use a cork board to cut cylinders.
  3. Trim cylinders to the same length.
  4. Measure length and mass of cylinders.
  5. Place cylinders in different sugar solutions.
  6. Leave overnight for osmosis.
  7. Roll on paper towel to remove moisture.
  8. Measure length and mass again.
  9. Calculate percentage change.
• What are the effects of osmosis on potato cylinders in different solutions?

  • In distilled water: Gains mass (water enters)
  • In concentrated sugar solution: Loses mass (water exits)
  • At equilibrium: No change in mass