To demonstrate a chemical change.
- Denture cleaner tablet
- 10-ounce (300-mL) clear plastic drinking cup
- Tap water
- Observe the appearance of the dry tablet. Record your observation in a Chemical Change Data table like the one shown.
- Fill the cup about half full with water.
- Drop the tablet in the water. Observe and record the results.
- Continue to observe and record the descriptions of the contents of the cup until there is no further change.
The tablet is green and solid when dry. When added to water, it vigorously produces bubbles for a time. Then the tablet appears to have disappeared, leaving a foamy green liquid.
The solid tablet combines with liquid water to form at least one new substance, a gas, as indicated by the bubbles. A process by which one or more substances, called reactants, are changed into one or more different substances, called products, is called a chemical reaction or chemical change.
In order for a chemical reaction to occur, the molecules of water must combine with the molecules on the surface of the tablet. This combination occurs because all particles of matter, such as the tablet and the water, have kinetic energy (energy of motion). This means the particles are in motion. In solids the motion is more of a vibration (back-andforth motion) around a center point, but in liquids the particles can move from one place to another. The motion of the water molecules causes random collisions with the tablet, resulting in a combination of the water molecules and molecules on the surface of the antacid tablet.
For Further Investigation
An increase of temperature is an indication of an increase of kinetic energy of a substance. Would the tablet disappear faster in hot water? A project question might be, How does temperature affect the speed of a chemical reaction?
Clues For Your Investigation
- Repeat the investigation using different water temperatures. Cold water can be made by adding ice cubs to tap water. Remove the ice cubes before adding the tablet. Cool water is tap water at room temperature. Hot water can be obtained from the tap. Repeat the experiment four or more times at the same temperatures. CAUTION: Ask an adult to fill the cups with hot water and to supervise handling of the cups of hot water:
- To measure the rate of the reaction, test one set of cups at a time, starting with the four cups of cold water. Observe the tablets and record the time the tablets are dropped in the water and the time each stops bubbling. Average this time. Repeat, testing the other two sets of cups (four cups of cool water and four cups of hot water) one at a time. Record your results in a Chemical Reaction Time Data table like the one shown.
References and Project Books
Churchill, E. Richard. 365 Simple Science Experiments with Everyday Materials. New York: Black Dog & Leventhal, 1997.
Heiserman, David L. Exploring Chemical Elements and Their Compounds. Blue Ridge Summit, Pa.: Tab Books, 1992.
Kenda, Margaret, and Phyllis S. Williams. Science Wizardry for Kids. Hauppauge, N.Y.: Barron's, 1992.
Kerrod, Robin. Simon & Schuster Young Readers' Book of Science. New York: Simon & Schuster, 1991.
Nye, Bill. Bill Nye the Science Guy's Big Blast of Science. Reading, Mass.: Addison-Wesley, 1993.
Strauss, Michael. Where Puddles Go. Portsmouth, N.H.: Heinemann, 1995.
VanCleave, Janice. Janice VanCleave's Chemistry for Every Kid. New York: Wiley, 1989.
Wiese, Jim. Rocket Science. New York: Wiley, 1995.
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.