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Chemical Reactions: Alka-Seltzer and Water Temperature

By — John Wiley & Sons, Inc.
Updated on Dec 13, 2010

A chemical reaction takes place when molecules collide with sufficient energy to break old chemical bonds and form new ones. Some reactions occur quickly, while others take place slowly. Temperature is one of the factors that can influence the speed of a chemical reaction. In this activity you will see how temperature affects the speed at which Alka-Seltzer reacts with water. Alka-Seltzer contains dried citric acid and sodium bicarbonate, or baking soda. When these chemicals are dissolved in water, they react, producing a fizz.

Materials

Safety goggles

One small paper cup half-filled with room-temperature water

One small paper cup half-filled with very warm (but not scalding) water

One small paper cup half-filled with cold water

Three equal-sized pieces of Alka-Seltzer

Activity

  1. Line up the cups of water in order from warmest to coolest.
  2. Put on your safety goggles. Simultaneously, drop a piece of Alka-Seltzer tablet into each of the cups.
  3. Compare the amount of fizz produced in each cup over the next few minutes. The fizz represents a chemical reaction occurring between the Alka-Seltzer and water.

Follow-Up Questions

  1. In which cup was there the most fizzing?
  2. Write a statement that explains how water temperature affects the speed of this chemical reaction.

Answers

  1. The warmest cup.
  2. As temperature increases, the speed of the reaction will increase.

Extension

See how surface area affects the speed of a chemical reaction. Use room-temperature water and two cups. In one cup place an intact Alka-Seltzer. In the other cup place an Alka-Seltzer that has been crushed into a powder. How do reactions in the two cups compare?

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