Required Practical 3: Effects of Osmosis on Plant Tissue

• What is the main focus of the investigation described in the video?

  The effect of osmosis on plant tissue
• Why is it important to learn the details of the required practical?

  Because it is a required practical that may be tested in exams
• What is osmosis?

  The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• What happens to plant cells when they are placed in water?

  Water moves into the cell by osmosis, causing the cell 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
  • Beetroot
  • Parsnip
• Why is the potato skin removed before the experiment?

  To prevent it from affecting osmosis
• How are the potato cylinders prepared for the experiment?

  They are cut to the same diameter and trimmed to the same length using a cork board and scalpel
• What is the recommended length for the potato cylinders?

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

  To assess the effect of osmosis on the cylinders
• 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
• What is the purpose of using distilled water in the experiment?

  It contains no dissolved substances that could affect osmosis
• How long are the potato cylinders left in the solutions?

  Overnight
• What is done to the potato cylinders after they are removed from the solutions?

  They are gently rolled on paper towel to remove surface moisture
• Why is it important not to press on the potato cylinders when drying them?

  To avoid forcing water out of the cells
• What steps are involved in calculating percentage change?

  1. Determine the change in value
  2. Identify the original value
  3. Use the formula:

  • Percentage change = (change in value / original value) × 100
• How do you calculate the percentage increase if the starting mass is 1.56 grams and it increases by 0.25 grams?

  16.03%
• How do you calculate the percentage decrease if the starting mass is 1.32 grams and it decreases by 0.19 grams?

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

  • In water, potato cylinders gain mass
  • In concentrated sugar solution, cylinders lose mass
  • The x-axis crossing indicates no change in mass
• What does it indicate when the graph crosses the x-axis?

  It indicates that the concentration outside the cell is the same as inside, resulting in no overall osmosis
• What is the approximate concentration inside the potato cells?

  The concentration where the graph crosses the x-axis
• What should students be able to do by the end of the video?

  • Describe how to investigate the effect of osmosis on plant tissue
  • Calculate percentage change