Growing Creatures

Demonstration Kit

Introduction

Watch your creature grow before your eyes! How big will it become? Let’s try and see!

Materials

Measuring the Growth of a Growing Creature
Water (distilled water preferred but not required)
Balance or scale (optional)
Growing creature
Quart jar or bowl (plastic preferred)
Ruler

Effects of Dissolved Solids on Growth of a Growing Creature
Water, distilled
Water, tap
Growing creatures (6 of the same creature)
Plastic containers or wide-mouth jars, 500-mL to 1-L capacity, 5

Effects of Salt on a Growing Creature
Salt (sodium chloride, NaCl)
Water, distilled water preferred
Bowl, plastic preferred
Growing creature
Jar or container for growing the creature

Safety Precautions

The material used in this activity are generally considered nonhazardous. Wash hands thoroughly with soap and water before leaving the laboratory.

Prelab Preparation

Effects of Dissolved Solids on Growth of a Growing Creature
Prepare solutions of table salt (sodium chloride, NaCl) in water:

  • 0.5% salt solution: Dissolve 2.5 g salt in 500 mL of water (½ teaspoon salt in 3 cups).
  • 1% salt solution: Dissolve 5.0 g salt in 500 mL of water (1 teaspoon salt in 3 cups).
  • 2% salt solution: Dissolve 10.0 g salt in 500 mL of water (2 teaspoons salt in 3 cups).

Procedure

  1. Examine the Growing Creature.
    1. What is the creature shaped like?
    2. Using a ruler, measure the creature. Use millimeters (mm) or centimeters (cm). How long is the creature? How wide is the creature? How thick is the creature?
    3. If you have access to a small scale, weigh the creature. (Be sure to tell the units of weight used.) How much does the creature weigh?
  2. Put the creature in a clean container, such as a water glass, jar, glass or plastic bowl. Fill the container with enough water to cover the creature. Record the current date and time.
  3. Check the creature at the time intervals indicated. Describe how it has changed.
    1. Changes after one hour. How long is the creature at this time?
    2. Changes after another hour (two hours total time). How long is the creature at this time?
    3. Changes at the end of four hours. How long is the creature at this time?
  4. Check the creature after about 8 to 12 hours (in the morning, if left growing overnight). Describe any changes. How long is the creature at this time? Record the date and time.
  5. Check the creature after about 24 hours. Describe any changes. How long is the creature? How wide is the creature? How thick is the creature? How much does the creature weigh? Record the date and time.
  6. If desired, the creature can be allowed to grow for a longer period of time. Check the creature at 24-hour intervals until growing stops.
  7. Remove the creature from the water. Let it dry out by putting it on a dry dish or in a dry pan.
    1. How long does it take for the creature to dry out?
    2. Did the creature shrink down to its original size? (You might want to measure and weigh the creature.)
  8. Place the creature back in water.
    1. How long does it take the creature to become full grown?
    2. Does your experiment indicate that the creature can be grown and dried out over and over without the creature falling apart?
  9. (Optional) Construct a graph to show the rate of growth of the Growing Creature. Construct a graph to show the rate of shrinking of the Growing Creature. Compare the two graphs.

Effects of Dissolved Solids on Growth of a Growing Creature

  1. Measure the length, width and thickness of the Growing Creatures. Record your measurements. (If balances are available, weigh the creatures).
  2. Place distilled water, tap water, and the salt solutions in five separate jars or containers. Place one Growing Creature in each solution and allow them to sit, undisturbed, overnight (about 24 hours, or longer if preferred). Keep one Growing Creature as a control.
  3. Remove the Growing Creatures and inspect them. Did they all grow?
  4. Measure the Growing Creatures (or compare them to the control). How much did they grow?
  5. What are the effects of dissolved materials in the water on the growth of a Growing Creature? (If desired, you can graph the results using length or weight/mass.

Effects of Salt on a Growing Creature

  1. Grow the Growing Creature in water for at least 24 hours.
  2. Remove the Growing Creature from the water and place it in a bowl.
  3. Sprinkle salt over the Growing Creature. Observe the Growing Creature. What is happening? Note: After the experiment, the Growing Creature can be rinsed off and reused.

Discussion

The purpose of this experiment is to investigate a Growing Creature. The small plastic creature swells up many times its original size when placed in water. The creature is composed of a plastic called a graft copolymer of hydrolyzed starch-polyacrylonitrile (polyacrylonitrile is commonly known as “Acrilan®,” “Orlon®” or “Creslan®”). Such materials are called super-absorbants or “super slurpers” and some are capable of absorbing up to 2,000 times their weight in distilled water. By combining the starch-polyacrylonitrile with glycerin or ethylene glycol (the active ingredient in anti-freeze), a strong and resilient plastic gel is produced that can absorb up to 400 times its weight in distilled water.

References

Special thanks to David A. Katz, retired, Wilmington, DE, who provided Flinn Scientific with the instructions for this activity.

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†Next Generation Science Standards and NGSS are registered trademarks of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.