Mr. Rowley
Science 10
Rates of Chemical Reactions Lab
Introduction:
Alka-Seltzer is a common, over the counter medication designed to relieve
symptoms stomach pain and discomfort while neutralizing excess stomach
acid. When the tablets are dissolved in water, they produce an effervescent
reaction releasing gas and bubbles.
Alka-Seltzer’s ingredients include: aspirin, sodium bicarbonate and citric
acid. As the tablets dissolve, the base (sodium bicarbonate) and the acid
(citric acid) react vigorously to produce carbon dioxide gas. This reaction
also produces enough agitation to allow the active ingredients to dissolve
slowly. The patient then ingests the resulting solution.
Purpose:
In this lab, we intend to observe the effect of temperature, surface area
and concentration on the rate of a chemical reaction.
Materials:
Alka-Seltzer tablets
Film canister with lid
Graduated cylinder
Bunsen burner
Water
Stopwatch
Metal scoop
Paper towel
Hypotheses: (4 marks)
Create a hypothesis for each of the following effects on the reaction rate
by circling the underlined word of your choice:
1. Hot water will increase/decrease the rate of the reaction
2. Cold water will increase/decrease the rate of reaction
3. Crushing the tablet will increase/decrease the rate of reaction
4. Using a larger sized tablet will increase/decrease the rate of reaction
Procedure:
Part 1: Establishing a control (This is what you will compare the rest of
your results against):
1. Using a graduated cylinder, measure 20ml of room temperature water
and place it in your film canister
2. Break an Alka-Seltzer tablet into two (2) pieces.
3. Place one half in the film canister with water and QUICKLY place the
cap on tightly
4. Using a stopwatch, time how many seconds it takes from the time the
tablet was dropped in the water to when the cap pops off
5. Record your time in your data table
6. Clean up the mess
Part 2: Testing the effect of temperature on the rate of a chemical
reaction:
7. Test the effect of cold temperature by REPEATING STEPS 1-6 with
cold water (use ice to cool your water)
8. Test the effect of hot temperature by REPEATING STEPS 1-6 with
hot water (use Bunsen burner to warm your water)
Part 3: Testing the effect of surface area on the rate of a chemical
reaction:
9. Obtain half of an Alka-Seltzer tablet and crush it into a fine powder
10. REPEAT STEPS 1-6 with the crushed half tablet
Part 4: Testing the effect of concentration on the rate of a chemical
reaction:
11. Obtain a full Alka-Seltzer tablet
12. REPEAT STEPS 1-6 with a full sized tablet
Data Table & Conclusion Questions
Trial
1. Room temp. water, ½
tablet
2. Cold water, ½ tablet
3. Hot water, ½ tablet
4. Room temp. water, ½
crushed tablet
5. Room temp. water, 1
full tablet
Time
Class Average
1. After completing the experiment, were your four (4) initial
hypotheses accurate? (2 marks)
2. What did your final results and the class average tell you about the
effects of temperature, surface area and concentration on the rate
of the reaction? (6 marks)
- Temperature:
-
Surface Area:
-
Concentration:
3. When Alka-Seltzer dissolves in water, the following reaction occurs:
The citric acid and sodium bicarbonate in the Alka-Seltzer tablet
react with water to produce carbon dioxide gas and sodium citrate.
Write a WORD EQUATION for the reaction. (5 marks)
4. What combination of all the factors we studied today would create
the FASTEST reaction? If you have time, feel free to try it out and
time it! (3 marks)