Pencils through a bag of water, kids science experiment

ByKarthik Kumar D Kon9th Aug 2023, 2023-08-09T08:45:00+05:30
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Pencils through a bag of water, kids science experiment

Title: Pencils Through a Bag of Water - Investigating Properties of Polymers Experiment

Objective: To demonstrate the unique properties of polymers and the concept of surface tension through the "pencils through a bag of water" experiment.


  • Ziplock bag (gallon size or larger)
  • Water
  • Pencils (unsharpened)
  • Optional: Food coloring


  1. Begin by discussing the concept of polymers with the children. Explain that polymers are large molecules made up of repeating smaller units and that many everyday items, such as plastic bags, are made of polymers.
  2. Gather the materials required for the experiment.
  3. Fill the ziplock bag with water, leaving some space at the top to prevent overflow when handling.
  4. Optional: Add a few drops of food coloring to the water to make it easier to see.
  5. Carefully seal the ziplock bag, ensuring it is tightly closed.
  6. Hold the bag of water firmly by the top, ensuring it doesn't leak.
  7. Take an unsharpened pencil and gently push it through one side of the bag, aiming to pass through both sides without causing any leaks. The pencil should go through one side of the bag, through the water, and out the other side.
  8. Repeat step 7 with additional pencils, spacing them out to create multiple pencil holes in the bag.
  9. Observe and discuss what happens to the bag of water. Notice that even though there are holes, the bag does not leak. The water remains inside the bag.
  10. Encourage children to make observations and discuss the concept of surface tension. Explain that surface tension is the cohesive force on the surface of a liquid that allows it to resist external forces, such as the pencils penetrating the bag.
  11. Reflect on the experiment and discuss the properties of polymers and how they contribute to the bag's ability to hold the water without leaking.

Safety Considerations:

  • Be cautious when using pencils to avoid injury. Apply gentle pressure and ensure proper handling.

This experiment allows children to observe the unique properties of polymers and surface tension by inserting pencils through a bag filled with water. It promotes scientific observation, critical thinking, and an understanding of basic chemistry and materials science concepts. Enjoy the exploration of polymers and surface tension with this engaging experiment.

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