Osmosis lab

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Chapter 7

• Osmosis lab

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Materials

• red onion
• forceps
• metric ruler
• Scissors
• paper towel
• iodine solution

• microscope slide
• coverslip
• dissecting probe
• microscope
• 10 salt solution
• distilled water

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Procedure

• 1. Use your fingers to separate one of the
  curved layers from the onion. Bend the layer
  until the shiny surface cracks. Look for a thin,
  clear layer of tissue at the place where the
  surface cracked. Use forceps to peel away some of
  the tissue. Use a scissors to cut away the
  tissue, if necessary.

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Procedure

• 2. Place a drop of iodine stain in the center of
  a clean glass slide. Use the forceps to place the
  onion sample in the drop of iodine on the slide
  and to gently flatten the tissue so that no air
  bubbles are trapped underneath the tissue.
• 3. Place a cover slip at an angle so that one
  edge touches the drop of iodine solution. Use a
  probe to slowly lower the cover slip over the
  onion tissue.

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Procedure

• 4. Use the space to draw the onion cells you see
  in the field of view. Choose one cell and label
  the cell wall, nucleus, and cytoplasm. The
  cytoplasm will be yellow. Note whether the
  cytoplasm completely fills the cell.

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Control

• 5. Put a few drops of salt solution at one edge
  of the coverslip. Hold a small piece of paper
  towel at the other end of the coverslip to draw
  the salt solution underneath the coverslip.

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• 6. After 3 minutes, observe the onion cells. Use
  the space below to draw the cells you see in the
  field of view. Choose one cell and label the cell
  wall, nucleus, and cytoplasm. Note whether there
  is any empty space between the cell wall and the
  cell membrane.

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After adding salt solution

• 7. Put a few drops of distilled water at one edge
  of the coverslip. Hold a new piece of paper towel
  at the other end of the coverslip to draw the
  distilled water underneath the coverslip.
• 8. After 3 minutes, observe the onion cells
  again. Use the space below to draw the cells you
  see the field of view. Choose one cell and label
  the cell wall, nucleus, and cytoplasm. Note
  whether the cytoplasm completely fills the cell.

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Add distilled water

• Repeat procedure using distilled water.