Cellular Osmosis Dehydration & Rehydration

60 mins Ages 7-9 Indoor

An engaging, screen-free learning activity that builds real-world creativity and critical thinking for kids aged 7 to 9.

Materials Needed

  • • Raw potato (1 unit)
  • • Table salt (2 tablespoons)
  • • Glass bowls (2 units)
  • • Metric ruler (1 unit)
  • • Paper towels (2 sheets)

Pro Tips

  • → Cut the potato strips into identical rectangular cylinders (e.g., 5 cm long by 1 cm wide).
  • → Have your child bend the potato strip before immersion to establish a baseline of firmness (turgor).
  • → Dissolve 2 full tablespoons of salt in the hypertonic bowl to maximize the osmotic concentration gradient.

Safety First

Adult slices the potato cores with a kitchen knife.

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Step-by-Step Instructions

1

Step 1

Cut two identical rectangular potato sticks measuring exactly 5.0 cm in length and 1.0 cm in width.

2

Step 2

Fill bowl 1 with plain tap water and bowl 2 with warm water mixed with 2 tablespoons of salt.

3

Step 3

Record the initial flexibility and length of both potato sticks, then submerge one in each bowl to soak for 35 minutes.

4

Step 4

Remove both sticks, pat dry, and re-measure: observe how the saltwater potato shrank and bends like rubber, while the freshwater potato became stiff.

What they are learning

Cellular semi-permeable membrane mechanics Hypertonic vs. hypotonic osmotic transport Turgor pressure and mass loss