Attractive: How Does Water Affect Pinto Beans?

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Author: Janice VanCleave


How does water affect pinto beans?


  • 1/2 cup (125 ml) dry pinto beans
  • clear plastic 2-cup (500-ml) measuring cup
  • tap water
  • timer


  1. Place the beans in the cup.
  2. Add enough water to the cup to cover the beans.
  3. Observe and record the volume (amount of space taken up) of the beans in the cup.
  4. Allow the beans to sit undisturbed for 24 hours.
  5. Attractive

  6. After 24 hours, observe and record the volume of the beans. Discard the beans.


After 24 hours, the volume of the beans has increased. Little or no water is left in the cup.


The volume of the beans increases while the volume of water decreases because the water moves into the beans. The beans are hydrophilic, meaning they have an attraction for water. The beans are also porous, meaning water can pass through them. The process by which a hydrophilic, porous material absorbs water is called imbibition. When dry seeds, such as the beans, are watered, they imbibe (absorb) water and swell.

Let's Explore

    1. How would excessive amounts of water affect the bean? Repeat the experiment, filling the cup with water.
    2. Do the beans imbibe water at a constant rate? Repeat the previous experiment. Record the volume of the beans on a chart similar to the one shown every 2 hours for 12 hours. Then record again once 24 hours after the experiment began, and once again 48 hours afterward. Science Fair Hint: Prepare and use a graph comparing the time and volume of the beans as part of a project display.
  2. Are other beans as hydrophilic as pinto beans? Repeat the experiment, using a different type of bean, such as lima beans. Compare the rate of change in volume of the different type of bean to the rate of change in volume of the pinto beans in order to determine which is more hydrophilic.


Show Time!

  1. How does imbibition affect the seed coat of a bean? Begin by recording the appearance of the seed coats of 2 dry pinto beans. Then, determine the hardness of the seed coats of the beans by scratching your fingernail across the seed coats. Place 12 beans in 1/2 cup (125 ml) of water. Three times daily for two days, remove 2 of the beans from the water and observe the appearance and hardness of their seed coats.
  2. Would pressure on the beans affect imbibition? Use fifteen 1000unce (300-ml) clear plastic cups. Fill 5 of the cups with pinto beans to a level of 1 inch (2.5 cm). Place a strip of masking tape down the side of each bean-filled cup. Mark the level of the beans on the tape. Cover the beans with about 1 inch (2.5 cm) of water.
  3. Fill the remaining 10 cups three-fourths full with sand. Place a sand-filled cup inside each of 4 bean-filled cups. The bottom of each sand-filled cup must rest on top of the beans. Stack the remaining sand-filled cups as shown. Mark the level of the beans every 2 hours for 12 hours. At the end of 12 hours, remove the sand-filled cups. Make a chart recording the level of the beans in each cup at each observation. Display the charted results.


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