Smithsonian National Air and Space Museum

Water Professional Development: Evaporation!


At our most recent Science in Pre-K training session we played with a new material…polymer water beads!

On May 6 we held a Science in Pre-K professional development session on Exploring Water for early childhood teachers from DCPS. As usual, we had a wonderful time exploring the special properties of water by engaging with water drops, water flow, and exploring how water interacts with other substances. This time we added a new material to our explorations – super absorbent polymer beads! This material is familiar to most of us as the gel-like stuff that make diapers work so well. They are also used for long lasting air fresheners and flower arrangements. The polymer beads start out tiny, but will expand up to 300 times their weight when placed in water. 

You can put the beads in water and measure how much they absorb and how long it takes them to reach their maximum size. It can take a few hours. Teachers thought the water beads would be a unique sensory experience for students. They have a slippery texture and would be good in a small bin or the water table. (Don’t let them go down the drain, they can cause clogs.) They are also beautiful on a clear tray on the light table because the light shines through them. The water beads are reusable, since they will shrink back down. Someone asked how long it takes for them to return to their original size, and this got us thinking about evaporation.

How could you experiment with polymer water beads to think about absorption and evaporation? 

The answer is- it depends! Evaporation is the process of a material drying out, or water molecules moving into the air as water vapor. You can explore evaporation with water colors on a coffee filter. Paint on the coffee filter and then observe what happens. Does the filter look and feel different after a few hours? Also explore evaporation by putting a drop of water on a paper towel. Draw around the drop to document the original size. Then observe and draw around the drop every 10 minutes. All of the materials that absorb water will eventually dry but where does the water go? It is in the air around us!
Many different factors affect the rate of evaporation. These include temperature, surface area, and air movement. If you lay your water beads out on a tray and direct a fan at them, they will shrink faster as the water will evaporate faster. If you leave your water beads in a bowl or bottle the water will stay in the beads longer. We put the beads in a bowl and after one week they had shrunk a little. The ones on the top were smaller than the ones at the bottom. Then we put them into a glass tube. After a month, the beads were still holding the water.

How could you experiment with water beads to think about absorption and evaporation?