Sunday, July 26, 2009

Water-grow Animals

Animals molded from polyacrylamide (the water-absorbing polymer used in diapers) will dramatically increase in size when immersed in water for several days. Such animals I call water-grow animals.

A great measurement activity for kids is to daily measure, record, and graph the change in length and width of a water-grow animal. Last summer, our two oldest grandkids, Joshua (Grade 3) and Jordann (Grade 2) placed a 15-inch alligator in grandmother’s bathtub and a week later it had grown to a length of 48 inches!

The kids liked the activity so much they wanted to repeat it during a recent visit. Only this time, each would choose a different animal.

Jordann chose a colorful frog that would fit in the palm of her hand.

Joshua liked a venomous cobra.

Before placing her frog in water, Jordann measured and recorded its length and width. As you can see in this picture, the frog is 3 1⁄2 inches long.

At this age, measuring to the nearest quarter-inch is sufficiently accurate. Later on, when measurement comparisons are made (e.g., the change in length from day to day), adding or subtracting quarters is easy for kids to compute.

Joshua’s snake measured 12 inches in length (no attempt was made to straighten the snake).

They recorded measurement data in separate tables and then graphed the data. I designed and printed the data and graph pages for them.

If you would like PDF files of these pages, email

Grandmotherscience was diligent in making sure Joshua and Jordann recorded and graphed measurements at the same time every day so that a daily growth rate could be computed.

At the end of their six-day visit, Joshua’s cobra had grown to over 48 inches!

And Jordann’s frog would no longer fit in the palm of her hand!

Both the snake and the frog are now drying on the patio and the kids will be eager to see if they return to normal size when they return in three or four weeks.

Water-grow animals can be purchased at most large retail outlets. If, like grandad, you like the convenience of ordering online, the following link has a large selection and good prices for water-grow animals.

Grandadscience will happily post water-grow animal pictures and measurement data from other kids (first names only).

Besides length and width, what other measurements could be made on a water-grow animal? What questions could be asked?

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