Written for PULSE by Christopher Martin
Edited By: Stephanie Nardei

20 minutes to print articles for students and load PowerPoint

Activity

1. Place a sugar cube into a beaker of cold water and let students observe the cube dissolve.
2. Ask students how they could increase the rate of reaction; dissolving the sugar in the water. Answers may include stirring, heating it up and crushing the sugar cube into powder.
3. Explains that increasing the temperature makes the molecules move faster and does affect the rate of reaction; and, crushing the sugar cube will increase the surface area.
4. Take a piece of magnesium ribbon and puts it into a beaker of 0.1molar Hydrochloric acid. The students observe that the reaction rate is slow. Students should discuss how the reaction rate can be increased.
5. Explain that by using a stronger acid, a more concentrated acid, the reaction rate can be altered. In some reactions, a catalyst or inhibitor can be used. They work by changing the activation energy.
6. Students will read the reaction rate lab, make predictions and do the four labs that illustrate the four factors affecting reaction rate.

Factoring affecting the rate of reaction

Temperature
Surface area
Concentration of reagents
Catalyst or inhibitor

Predictions
Increasing the temperature will increase/decrease the rate of reaction.

Increasing the concentration of the reagents will increase/decrease the rate of reaction.

Increasing the surface area of the reagent will increase/decrease the rate of reaction.

Adding a catalyst will decrease the activation energy. This will increase/ decrease the rate of reaction.

Adding an inhibitor will increase the activation energy. This will increase/ decrease the rate of reaction.

LAB: To determine the affect on rate of reaction of increasing the temperature.

Method
Pour 200 ml of water into a beaker. Record the temperature. Add an antacid tablet to the water and record the time that it takes to dissolve. Heat 200 ml of water. Record the temperature. Add an antacid tablet to the hot water and record the time that it takes to dissolve.

Results

Conclusion

Temperature increases/ decreases the rate of reaction.

LAB: To determine the affect on rate of reaction of increasing the surface area.
Method

Pour 200 ml of water into a beaker. Add an antacid tablet to the water and record the time that it takes to dissolve. Use a pestle and mortar to crush an antacid tablet. Add the powder to a second 200 ml. of water and record the time taken to dissolve.

Conclusion

Increasing the surface area increases/ decreases the rate of reaction.

LAB: To determine the affect on rate of reaction of increasing the concentration of reagent

Method
Wear goggles. Cut a strip of Magnesium ribbon 2cm long. Use a measuring cylinder to measure 50ml. of 2molar Hydrochloric acid. Add the Mg ribbon to the acid and record the reaction time. Prepare 1M, 0.5M and 0.2M solutions of hydrochloric acid by dilution and measure the reaction time with the dilute acids.

Results

Graph your results with concentration on the X axis and reaction time on the Y axis. Use graph paper. Write a balanced chemical equation for the reaction.

Conclusion
Increasing the surface area increases/ decreases the rate of reaction.

LAB: To determine the affect on rate of reaction of using a catalyst

Method
Pour 20 ml of Hydrogen peroxide into a boiling tube. Record your observations. Add a small amount of Manganese dioxide and record your observations

Balance the equation
H2O2 à H2 + H20

Conclusion
Adding a catalyst increases/ decreases the rate of reaction.

Earn Extra Credit

Define activation energy and draw a diagram to explain how a catalyst will affect the activation energy. Find out how Graphite is used as an inhibitor in a nuclear power station.

Homework
Students should review what they learned.

Embedded Assessment
Completion of the experiments and correct conclusions based on individual results will indicate understanding.