Required Practical 3:Effect of Osmosis on Plant Tissue (T)

• What should you be able to describe by the end of the video?

  Investigate the effect 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 in, causing cells to expand
• What occurs when plant cells are placed in a concentrated solution?

  Water moves out, causing cells to shrink
• What type of 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?

  Cork board
• Why do we trim the potato cylinders to around three centimeters?

  To measure the effect of osmosis accurately
• What is the first step after preparing the potato cylinders?

  Measure the length and mass of each cylinder
• What volume of sugar solution is added to the first test tube?

  10 centimeters cubed
• What concentration of sugar solution is used in the first test tube?

  0.5 molar
• Why do we use distilled water instead of tap water?

  Distilled water has no dissolved substances
• How long do we leave the potato cylinders in the solutions?

  Overnight
• What should we do after removing the potato cylinders?

  Gently roll them on paper towel
• Why is it important not to press on the cylinders?

  To avoid forcing water out of cells
• What do we measure after rolling the potato cylinders?

  The length and mass of the cylinders
• How do we calculate percentage change?

  Change in value divided by original value
• What is the percentage change formula?

  $\text{Percentage change} =$$\frac{\text{Change in value}}{\text{Original value}} \times 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 show?

  Mass gain in water, loss in concentrated solution
• What does it mean when the graph crosses the x-axis?

  No change in mass occurs
• What does the concentration at the x-axis crossing indicate?

  Approximate concentration inside the cell
• What are the steps to investigate osmosis on plant tissue?

  1. Peel the potato.
  2. Use a cork board to create cylinders.
  3. Trim cylinders to the same length.
  4. Measure length and mass of each cylinder.
  5. Place cylinders in different sugar solutions.
  6. Leave overnight for osmosis to occur.
  7. Roll cylinders on paper towel.
  8. Measure length and mass again.
  9. Calculate percentage change.
• What are the key points about calculating percentage change?

  • Formula: $\text{Percentage change} =$$\frac{\text{Change in value}}{\text{Original value}} \times 100$
  • Change in value can be positive or negative.
  • Important for analyzing osmosis results.
• 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.