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Expander: What Happens to a Latex Sponge in Water?

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Author: Janice VanCleave

Problem

What happens to a latex sponge in water?

Materials

  • latex
  • dishwashing sponge
  • magnifying lens
  • tap water
  • saucer
  • Scissors
  • ruler

Procedure

  • Stand the dry latex sponge on its long edge. If necessary, hold it upright.
  • Observe the upturned side of the sponge with the magnifying lens.
  • Describe the appearance of the sponge as viewed through the magnifying lens. Make a diagram to represent your description.
  • Pour enough water into the saucer to cover its bottom.
  • Cut a ½-inch (1.3-cm) square section from the dry sponge.
  • Stand the small sponge section in the water.
  • With your unaided eye, observe any change in the size of the sponge.
  • Use the magnifying lens to observe the surface of the sponge.

Expander

Results

The surface of the dry sponge has holes that vary in size and shape. The color of the sponge is not significant because color is added by the manufacturer. Adding water causes the surface of the sponge to expand slightly in all directions. After the addition of water, the sponge, as viewed through a magnifying lens, looks wet and shiny, with holes that are slightly larger than when the sponge was dry.

Why?

Sap from rubber trees is called latex. Chemicals are added to this liquid sap, and the mixture is then whipped into a foam. The foam is poured into molds, heated until dry, cooled, and then removed from the molds. It is now a soft material with air spaces throughout. This spongy, water-absorbing material is used to clean everything from dishes, cars, and dogs to your body. This factory-made sponge behaves very much like a natural sponge in its ability to absorb water. Both the factory-made sponge and the natural sponge have open spaces that allow water to move from one cavity to the next. As the water fills each space, the sponge expands.

Try It With A Microscope

Microscope Procedure

  1. Use scissors to cut a thin slice from the dry sponge.
  2. Use your fingers to stretch the sponge slice as much as possible, then place the slice onto a microscope slide.
  3. Expander

  4. Under low power, observe the sponge. Use a dissecting probe or straightened paper clip to move the slice around until the best view of the holes of the sponge is located.
  5. Hold the sponge against the slide with the probe. At the same time, place drops of water next to one side of the sponge using an eyedropper.

Microscope Results

The dry sponge appears as a dark object with irregular-shaped holes. The holes close when the water is added.

Let's Explore

  1. Are all liquids absorbed by a dry sponge? Repeat the original experiment using different liquids such as syrup, mineral oil, and rubbing alcohol. WARNING: Keep rubbing alcohol away from your mouth and nose.
  2. Does a natural sponge behave in the same manner as a latex sponge? Repeat the original experiment using a natural sponge.

Show Time!

Living sponges are very unusual animals found in aquatic (watery) environments. The thin layer of flattened, protective cells covering the surface of a sponge is punctured with tiny holes. Water is able to move through the openings in both the real and the factory-made sponges. Use different samples of factory-made and living sponges. Cut equal-sized pieces from each sample. Compare the amount of water that each will hold by submerging each piece in a bowl of water and squeezing the water into a measuring cup. Display the samples with the experimental results.

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