Osmosis

• 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 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 is the typical vegetable used to investigate osmosis?

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

  To prevent the skin from affecting osmosis
• How do we ensure the potato cylinders are the same diameter?

  Using a cork borer to cut them
• What length should the potato cylinders be trimmed to?

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

  To assess the effect of osmosis accurately
• How much of the 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
• How long do we leave the potato cylinders in the solutions?

  Overnight
• What should be done 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 the cells
• How do you calculate percentage change?

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

  Percentage change = (change/original) × 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 concentration show?

  • Gains mass in water
  • Loses mass in concentrated sugar
  • No change at isotonic concentration
• What does it mean when the graph crosses the x-axis?

  There is no change in mass
• What does the concentration at the x-axis crossing indicate?

  Approximate concentration inside the cell
• What is a key aspect of the required practical on osmosis?

  • Understanding osmosis
  • Calculating percentage change
  • Conducting experiments with plant tissue