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Science Fair Projects for Seventh-Graders Involving the Dissolving of Sugar Cubes & Alka-Seltzer

by Jennifer VanBuren

The best middle school science fair projects can be cheap, quick and straightforward. By studying the effect of easily controlled variables on the rate of the chemical reaction of Alka-Seltzer and solution rate of sugar cubes, students gain experience with all the elements of the scientific method, including controlled variables, repeated trials, careful analysis of the data and formally presenting the process.

Effects of Temperature on Chemical and Physical Changes

Chemical changes result when new products are formed.

Place one tablet of Alka-Seltzer in the bottom of the cup.

Pour the ice water into a cup until it is about 3/4 full, and start your timer

Stop the timer as soon as the bubbles stop.

Repeat steps 1 to 3 using room temperature, warm and then hot water.

Complete three trials for each temperature water.

Experimentation formalizes the familiar process of dissolving sugar.

Repeat the entire experiment, using a sugar cube instead of Alka-Seltzer.

Effects of Surface Area on the Rate of a Chemical and Physical Changes

Place a whole Alka-Seltzer tablet in the bottom of a dry cup.

Pour room temperature water into the cup, and start the timer.

Stop the timer as soon as the bubbles stop.

Break an Alka-Seltzer tablet into large chunks -- approximately four to six pieces -- and repeat steps 1 through 3.

Crush Alka-Seltzer into a powder using a mortar and pestle, or by placing it in a plastic bag and using a rolling pin or tin can to crush the tablet. Repeat steps 1 through 3.

Complete three trials for each variable: whole, pieces and powder.

Repeat the experiment using sugar cubes, measuring how long the cube takes to dissolve.

Items you will need
  • 21 Alka-Seltzer tablets
  • 21 sugar cubes
  • Beakers or clear plastic cups
  • Ice water (0°C)
  • Room temperature water (22 degrees C)
  • Warm water (40 to 50 degrees C)
  • Hot water (70 to 80 degrees C)
  • Mortar and pestle or a rolling pin
  • Plastic bag
  • Timer

Tips

  • Since the chemicals in Alka-Seltzer need to dissolve in order to react, you should find similar results. The hotter the water, the faster the water molecules are moving and the faster the Alka-Seltzer and sugar will dissolve. The big difference is that the Alka-Seltzer changes chemical composition, and the sugar cube just dissolves.
  • When timing the reaction, you will see that the majority of the bubbles stop at the same time. Don't wait until every single bubble has erupted. Consider doing a practice run without recording data.
  • Take photos. They are great way to dress up your project board and illustrate your process.

Warnings

  • Wear safety glasses when crushing Alka-Seltzer. While it is a safe material, the powder can irritate your eyes.
  • Drop the tablet into a dry cup or the reaction will start before you pour in the water.

About the Author

With degrees in biology and education, Jennifer VanBuren now utilizes her research and instructional skills as a writer. She has served as educational columnist for "Austin Family Magazine" for four years and also reports on area businesses for "Faces and Places" magazine.

Photo Credits

  • Brand X Pictures/Stockbyte/Getty Images