Name: _____________________________
Lab Investigation: Factors that Affect Reaction Rate
Introduction:
You may have noticed that chemical reactions occur at different rates. The explosion of
fireworks is instantaneous; the rusting of an iron gate is relatively slow. A rate is measure of change
per unit time. For example, the rate of change of distance over time is called speed. The rate of a
chemical reaction is studied in terms of changes in concentration of a reactant or product over time.
Chemists study rates of reaction in order to control the progress of a chemical reaction. In
order to understand how the rates of chemical reactions can be controlled, it is necessary to
understand the factors that influence the rates of chemical reactions.
In this experiment, you will study the effect that temperature and particle size have on the rate
of a chemical reaction.
Materials:
Alka-Seltzer tablets (1 packet)
stop watch
mortar and pestle
5% acetic acid (vinegar)
three clean beakers
water (cold, warm)
stirring rod
Procedure:
1. Obtain a packet of Alka Seltzer tablets. Divide the two tablets into four equal portions (i.e. break
each in half).
2. Obtain 100 mL of warm water from the sink or a hot plate. Record its temperature.
3. Obtain half of an Alka-Seltzer tablet and prepare to start timing.
4. Drop the tablet into the water and begin timing.
5. Stop timing once the reaction has visibly slowed down (no more gas produced).
6. Record the reaction time. Rinse content of beaker down drain.
7. Repeat steps #3-7 using cold water.
8. Obtain half of an Alka-Seltzer table and place into muffin cup inside a mortar and pestle.
9. Grind the tablet into a fine powder.
10. Obtain 100 mL of room temperature water in a clean beaker. Record its temperature.
11. Empty the powdered tablet into the water and begin timing. Stir gently with a stir rod to keep the
powder from floating on the surface. Stop timing when the reaction slows down.
12. Measure 100 mL of 5% acetic acid into a beaker.
14. Obtain half of an Alka Seltzer tablet and prepare to start timing.
15. Drop the tablet into the water and begin timing.
16. Stop timing once the reaction has visibly slowed down (no more gas produced).
17. Record the reaction time. Rinse content of beaker down drain.
18. Clean all beakers using soap and water. Clean laboratory station and return materials.
(continued on back)
Data:
Reaction
Reaction Time (seconds)
Warm Water
(temp = _____ oC)
Cold Water
(temp = _____ oC)
Powdered Tablet
Tablet with 5% Acetic Acid
Conclusions: Answer each of the following in complete sentences.
(1) How does temperature affect the rate of a reaction (i.e. does an increase in temperature make the
reaction go faster or go slower)? Discuss your results for cold and warm water.
(2) By grinding the tablet, what did we do to the exposed surface area? ___________________
What effect did this have on the rate of the reaction (faster or slower)? Why?
(3) When you added additional acid to the reaction, what effect did this have on the rate of the
reaction (faster or slower)? Why?
(5) Using your data, complete the following statements with either the word “increase” or “decrease”.
1. To increase the rate of a reaction, you should ________________ temperature.
2. To increase the rate of a reaction, you should ________________ surface area.
3. To increase the rate of a reaction, you should ________________ concentration.