Explode-A-Grape Lab

Explode-A-Grape Lab

Explode-A-Grape Lab

Introduction: Diffusion is the movement of particles from an area of high concentration to an area of low concentration. Osmosis is the diffusion of water, often across a semipermeable membrane, such as the cell membrane, or grape skin. Solutions that are hypertonic cause water to leave the cell (or grapes), while hypotonic solutions cause water to flood inside of the cell (or grapes). Osmotic pressure can sometimes be so great that membranes (or grapes) burst.

Objective: Students will witness and understand osmosis and diffusion.

Materials (per group):

  • Two grapes
  • Distilled water
  • Graduated cylinder
  • Beaker
  • Measuring tape
  • Two plastic cups
  • 3 to 4 tsp. Sodium chloride
  • Masking tape
  • Stir sticks

Directions:

  1. FRIDAY: Mix the sodium chloride with the 100 mL distilled water in the glass beaker. Mix in as much salt as will dissolve – the more the better! Use the stir stick to make sure you water is fully saturated with sodium chloride.
  2. Label one of the cups “fresh” and the other one “saline.”
  3. Measure and record the circumference of each grape and record it in the table below.
  4. Measure and record the mass of each grape and record it in the table below.
  5. Place one grape in each cup.
  6. Fill each cup with either saline solution or 100 mL distilled water, depending on labels.
  7. Find a safe place in the back of the classroom to store your cups for the weekend.
  8. Make sure you put your names on your cups so you know which one is yours on Monday.
  9. MONDAY: Dump your water out in the sinks and gently pat dry your grapes (try not to squish them).
  10. Measure and record the new circumference of each grape and record it in the table below.
  11. Measure and record the new mass of each grape and record it in the table below.

Data Table

Initial Circumference (mm) / Initial Mass (g) / Final Circumference (mm) / Final Mass (g)
Grape – Fresh Water
Grape – Saline Water

Conclusion

  1. Which grape ruptured? Did you expect this? Why or why not?
  1. Which grape shriveled? Did you expect this? Why or why not?
  1. Which cup contained the hypertonic solution? How can you tell?
  1. Which cup contained the hypotonic solution? How can you tell?
  1. In your own words, explain why your grape exploded (on a molecular level, what happened?).
  1. What do you think might happen if the cells in your body were exposed to ocean water?
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