Wonderful Waterlock

Introduction:

Successful science depends largely on our ability to make careful observations of the world around us. Demonstrations that highlight the importance of precise watching can be interesting and fun for kids. In this activity, we will  use one of the most unusual and amazing substances ever created to illustrate how observations play an critical role in the development of new knowledge and ideas.

National Science Standard: Unifying Concept

Nature is predictable and we can use evidence to explain and understand it.

Georgia Performance Standards:

Students will exhibit curiosity, honesty, openness and skepticism S(K-5)CS1

Describe materials, what they are made of, and how they change. SKP1, S2P1,S5P2

Materials: 

Safety goggles

Teacher Led Exploration:  

We begin this exploration by playing the shell game using three cups instead of three shells. The cups need to be identical, opaque, and white on the inside. Place about 1/4th of teaspoon of Waterlock into two of the cups before students come into the class. Have the three cups placed out on a table for your students to see. 

Tell the students that you are about to do a demonstration that will test how good they are at making observations. Their job is to follow the cup with the water in it as you scramble the cups around and around. Show them that the cups are empty by tipping them sideways in their direction (they will not be able to see the white powder). Pour about 1/4 cup of water into one of the cups that has the Waterlock in it and then scramble the cups around for a minute or so (the Waterlock will absorb the water and gel it in the bottom of the cup). After moving them around, have the students vote on the cup that they believe contains the water.  Students generally have no trouble following the correct cup.  Next, carefully invert the one empty cup to show them this obviously isn't the right one. Finally, invert the cup that they all voted on watch their surprised reaction when no water flows from the cup.  Repeat this process using the second cup that contains Waterlock. 

Now ask students to develop ideas to explain what happened to the water. Encourage them to think of as many ideas as possible and let them discuss their ideas in small groups for a minute or two.  Then discuss these ideas as a group encouraging them to be creative and "out of the box" in their thinking. 

After this discussion you can tell the students that two of the cups actually contained a small amount of one the most amazing substances on the planet, Waterlock (sodium polyacyrlate). Using a spoon, show them that it is white powder that looks quite usual and ordinary. Then place a small teaspoon of this powder into a clear cup and mix it briefly. Allow the students to observe the Waterlock as it quickly absorbs the water. After a few seconds, you can invert the cup to show that water will not pour out.  You can also tap the inverted cup on the table until the gelled water falls out. You can them pick it up like a snowball and show it to the rest of the class. 

Although Waterlock is not toxic, you should avoid letting students touch it because if crystals get from their fingers to their eyes it can be very irritating. Anyone who does touch the Waterlock should rinse their hands thoroughly after the demonstration. 

 Essential Questions:

1. What do you think happened to the water inside the cup?

2.   If you invented this substance, what could you use it for and how could you sell it to make a profit?

3.  Do you think that there is anyway to reverse this process to get the water and Waterlock back to their original state? If so, how would you do it?

4. Write a commercial, song, poem, or info-mercial that you could use to sell Waterlock to the rest of the world.

Explanation:   

Since this is a teacher-led exploration, class discussion occurs during the course of the exploration.  

Concept Building:  

This is a great demonstration because the cup demonstration is very counterintuitive and thus it is curiosity stimulating and thought provoking. It helps students to recognize the importance of making good observations and it allows them to see how substances can undergo amazing changes when combined together. Waterlock is a molecule that has an amazing ability to absorb up to 800 times it's own weight in water. That means that if you were a 100 pound chunk of this stuff and you jumped into a swimming pool, you would absorb over 80,000 pounds of water from the pool.  As a result Waterlock is used often in places where water and water-based spills are a problem. For example, Waterlock is used by plumbers to gel up the water from leaky pipes before it can soak in and cause major damage. But the most famous and profitable use of Waterlock is in diapers where it is sewn into the fabric so that the babies urine (mostly water) gels rather than leaking through the diaper and pants.  

As a side note, substances, including water,  usually move from where is more crowded to where it is less crowded (from higher to lower concentrations). The water molecules move into the center of the sodium polyacrylate molecules because there is less water on the inside then there this on the outside.  This causes the water to "gel". You can reverse the process by adding sodium (table salt) to the glass and stirring it.  

Teacher Notes:

Waterlock (sodium polyacrylate) can be purchased from www.teachersource.com

Safety Concerns:

Although Waterlock is not toxic, you should avoid letting students touch it because if crystals get from their fingers to their eyes it can be very irritating. Anyone who does touch the Waterlock should rinse their hands thoroughly after the demonstration.  You can dispose of it by washing it by throwing it away or washing it down the sink with a lot of water.

Extension: 

New uses for Waterlock are being developed every year. Have students brainstorm additional ways that Waterlock could be utilized to improve our communities. As a homework assignment or extra-class activity, have students determine how much water a disposable diaper can hold before it starts to drip. Have them slowly add water (distilled works best) one cup at a time and see how much the diaper can hold. It is amazing. You can color the water yellow if you want to and it should hold at least a liter of water.  

Evaluation:

Students should draw/outline/discuss their ideas about Waterlock in their science journals.