PACT Due Dates

Osmosis with Grapes (Sarah Ishida)

Title: Grape Osmosis in Hypotonic, Hypertonic, and Isotonic Solutions Lab

Principle(s) Investigated: The concentration of a solute in a solution will affect the movement of water in and out of grapes.


Standards :

Cell Biology-

1. The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells.

1a. Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.

Materials:
  • Grapes
  • Water
  • Sugar/Corn Syrup
  • Grape Juice
  • Small Cups/Jars
  • Stirring Rod
  • Paper Towels
  • Digital Scale
  • Masking Tape

Procedure:

  1. Label three small cups Sugar Water, Grape Juice, and Water using masking tape.
  2. Put sugar and water at a 1:1 ratio in the Sugar Water cup and stir with a stirring rod.
  3. Measure the mass of a grape using the digital scale, record in data table, and place in the Sugar Water cup.
  4. Put grape juice in the Grape Juice cup.
  5. Measure the mass of a grape using the digital scale, record in data table, and place in the Grape Juice cup.
  6. Put water in the Water cup.
  7. Measure the mass of a grape using the digital scale, record in data table, and place in the Water cup.
  8. Let them set for 24 hours.
  9. Take out the grape from the sugar water, and dry carefully using a paper towel.
  10. Measure the mass of the grape and record in data table.
  11. Take out the grape from the grape juice, and dry carefully using a paper towel.
  12. Measure the mass of the grape and record in data table.
  13. Take out the grape from water, and dry carefully using a paper towel.
  14. Measure the mass of the grape and record in data table.

Student prior knowledge:

Students should understand that grapes are made of cells, and in addition to each of their cell membranes, the skin of the grape is also a semi-permeable membrane.

Students should understand that water moves from high to low concentration.

Explanation:

When the grape is placed in sugar water, a hypertonic solution, water will move down the concentration gradient from high concentration (in the grape) to low concentration (the solution), causing it to shrink.

When the grape is placed in grape juice, an isotonic solution, water will not move across the semi-permeable membrane because water concentration is equal on both sides of it.

When the grape is placed in water, a hypotonic solution, water will move down the concentration gradient from high concentration (the water) to low concentration (in the grape), causing it to swell.

Questions & Answers:

Q: Name sources of error in this experiment.
A: The grape juice may not have the same concentration of sugar as the grapes, and slight osmosis may happen in either direction. If the grapes are not dried properly, it will alter the ending mass.

Applications to Everyday Life:

Grocery stores periodically spray water on their produce so that osmosis will occur and keep them fresh and crispy.

If a person drinks saltwater for long periods of time, the cells in their body will become dehydrated and die.

If salt is put on a slug, it will pull out the water in the slugs cells, causing it to shrivel up.

Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.

Videos:

Osmosis in a Sucrose Solution

Google Doc:

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