Introduction: Alka Seltzer tablets are taken to neutralize an acid stomach. In this experiment, you will use cola to represent an acid stomach, and compare the effect of a solid tablet, with a crushed tablet.

RQ: How does the addition of Alka Seltzer affect the pH and Temperature of an Acidic solution?

Task 1: Make a Prediction: increase, decrease, stay the same

pH _Temperature

Task 2:

Independent variable:

Dependent variable:

Factors to be controlled:


Task 3:

Make a materials list

Task 4:

Design a method for the above research question. Make sure to describe all equipment needed

Task 5:

List any safety concerns.

Task 6: Run the experiment.

Task 7: Results

Task 8: Conclusion and Evaluation

Questions for Evaluation

1. 1. What does the pH graph tell you about the reaction between acid and the alka seltzer?

2. 2. Does the pH change most slowly at the beginning, middle, or at the end?

3. 3. When does the pH change most rapidly?

4. 4. Describe the temperature change?

Student Work: Paste your work below under your heading

Lab Experiment
Task 1. Prediction:
I believe that if you put Alka Seltzer in coke (which represents the stomach acid) then the pH will go up and the solution will become less acidic. If the Alka Seltzer tablet is crushed then it will react faster in the stomach(coke) whereas the solid tablet will take time to break down and therefore work slower.
Task 2.
Independent Variable: One tablet which will be crushed and the other will be solid.
Dependant variable: the speed at which the tablet affects the pH of the stomach acid (coke) and how much the pH has been affected.
Factors to be controlled: The temperature of the coke will be cold.
Hypothesis: If I drop a crushed Alka Seltzer tablet into coke then it will affect the pH of the coke faster than if you dropped a solid Alka Seltzer tablet into the coke.
Task 3: Materials
· Alka Seltzer tablets (some crushed)
· Coke bottle x 1
· Beakers for the coke x 2
· pH sensor x 2
· computer x 1
· Vernier data collector x 1
Task 4: Method

  1. Fill the two beakers with coke.
  2. Connect the pH sensors to the computer.
  3. Put one sensor per beaker of coke.
  4. Record its starting temperature and pH.
  5. Then drop the solid Alka Seltzer tablet in one beaker and the crushed Alka Seltzer tablet in the other beaker.
  6. Then record the changes in the coke’s pH.

Task 5: Safety concerns
- Keep beakers away from the edge of the tables.
- During a lab you should always wear gloves and goggles.


Task 1: Prediction

I predict that the pH will increase because of the alkalinity of the Alka Seltzer and that the temperature will increase as well because the particles are moving faster while the tablet dissolves therefore increasing the temperature.

Task 2: Prediction

The independent variable is the Alka Seltzer tablet and the dependent variable is the pH and temperature.
The factors to be controlled are the amount of cola that is used and the temperature that it is while performing the experiment. Other factors to be controlled are how long you wait to test the pH and temperature and also how much cola you choose to use for the experiment.


I think that if a full tablet is dropped into the cola the pH and temperature will both increase more than it would for the crushed tablet. I feel that this is because the tablet, when placed in as a whole, requires more work to dissolve it therefore causing particles to move quicker and in turn increase heat. I feel that the pH will also be increased because the tablet as a whole is stronger than it would be crushed and would have more of an alkaline effect on the cola causing the acid level to be reduced.

Task 3: Materials

  • Two 100 mL beakers
  • Two cold cans of cola
  • Four to six Alka Seltzer tablets (some crushed, some not)
  • Data logger
  • Temperature probe
  • pH probe
  • Computer
  • Timer

Task 4: Method

  1. Connect the data logger to the computer and attach both the pH and the temperature probe.
  2. Fill both beakers will 30 mL of cola and use the pH to test and record the starting pH value.
  3. Use the temperature probe to test the starting temperature of the cola and record the value.
  4. Crush one Alka Seltzer tablet .
  5. Place a whole Alka Seltzer tablet in on beaker and the crushed one in the other.
  6. Let the tablets dissolve for 1 minute.
  7. After the time is up place the pH probe back in the cola and record the pH value.
  8. Test the temperature of the solution to find the temperature after the tablet as dissolved and record the value.
  9. Repeat the lab with new tablets and fresh cola to get the most accurate results.
  10. Compare your results to see which pH was altered the most.

Task 5: Safety Precautions

To ensure safety make sure to wear goggles and gloves as well as making sure that your beakers are not near the edge of the tables to prevent them from falling and breaking.


RQ: How does the addition of Alka Seltzer affect the pH and temperature of an acidic solution?
Introduction: Alka Seltzers are tablets that are used to neutralize an acid stomach. In this experiment, you will be testing the effects that Alka Seltzers has on coca cola, which is representing the acid stomach. You will test to see if the effects differ between using a whole tablet and a crushed tablet.
Prediction: I predict that the effects will not differ when you are using a whole tablet compared to a crushed tablet in the pH and temperature of cola. I predict the pH of the solution will decrease as the purpose of the tablet is to neutralize. I predict that the temperature will not be affected, therefore staying the same.
The independent variable in this experiment is the crushed and the whole tablet. The dependent variable in this experiment is pH and the temperature of the cola. The factors to be controlled are the start temperature and pH of the cola. My hypothesis is that if I put a whole and a crushed Alka Seltzer tablet into two different beakers of cola, then the outcome will be that the pH will increase, the temperature will not be affected and there won’t be any changes if the two solutions were compared.
- pH sensor
- Temperature sensor
- Coca Cola
- Two Alka Seltzer tablet
- Spoon or knife
- Two 100mL beakers
1. Start the experiment by pouring 60mL of coca cola into two different 100mL beakers.
2. Test the temperature and the pH and make sure they are equal to each other, so that the pH and temperature will not affect the outcome.
3. Drop 1 whole Alka Seltzer tablet into the first beaker and label it solution A.
4. Crush 1 whole Alka Seltzer tablet with a knife or spoon on a clean surface, and pour into the other beaker, labeling this solution B.
5. Leave for 1 minute.
6. Test the pH and temperature of both, washing both sensors in between using them, and take down the results.
7. Compare the results, noting the initial temperature and pH compared to the final temperature and pH.
8. Now compare the two final solutions to each other, and note down if there are any differences between solution A and solution B.

- Be aware that the experiment could be altered if the pH sensors are not cleaned between using them and this will affect your final outcome.
- Do not test the Alka Seltzer by adding it into water and drinking it, unless in your stomach really is upset. Any medicine should not be taken, unless necessary.


Solution 1 (Whole Tablet)
Solution 2 (Crushed Tablet)
Initial temperature
Initial pH
New temperature
New pH

external image clip_image002.gifexternal image clip_image004.gif

The pH was the most obvious changing subject in this experiment, as it dropped quickly first in the graph, and ended up slowing down at the end once it reached above 6 on the pH scale. This relationship shows that the Alka Seltzer, when added in water, would not do any major changes to the water, however actually doing a test with water would show if there are any major changes, however the ingredients are now added to the water, meaning that once it reaches your stomach the ingredients will still work to put an end to a acid stomach, and make it less acid. There were no major changes in the temperature, however small changes such as a 1 degree change which should still be noted.
In the conclusion to the experiment of what the effects from an Alka Seltzer, being crushed or whole and dropped in to a coke, would be I found that the Alka Seltzer generally turned the acidic coke back to near water pH, which means more neutral pH. My hypothesis was partly proved, meaning that the pH would increase once added to the cola. My hypothesis was also a little untrue, meaning that I believed originally that there would be no temperature and no changes between the two solutions, however there were small, but notable, changes between the two solutions. I think maybe this is because the crushed Alka Seltzers was stronger as it diffused into the cola with a stronger power, also fizzing up the cola a lot more than the whole tablet did. This was something that I noticed, however it was not part of my original theory. So in the end, I learned that Alka Seltzer, if used as a whole tablet, will work fast. If used crushed it will fizz up the water, and act a little faster when taken with water to settle an acid stomach.


Task 1:

I predict that when you compare the effect of a solid tablet with a crushed tablet that the pH and temperature will both stay the same with either of the tablets.

Task 2:

Independent Variable:
Alka Seltzer

Dependent Variable:
pH and temperature

Factors to be controlled:
Make sure neither of the cokes have been shaken
Make sure that both the cokes are new and have not been opened
Make sure that each experiment is taken in the same place to avoid the temperature to be different in one coke than the other
Make sure that each coke has the same amount of liquid in it
Make sure that each coke is the same brand of coke (e.g Coca Cola)

If I compare the effect of both a solid tablet and a crushed tablet of Alka Seltzer dropped in coke then both the pH and the temperature will stay the same throughout both experiments.

Task 3:

- Two bottles of coke
- One solid Alka Seltzer tablet
- One crushed Alka Seltzer tablet
- 2 X 250ml beakers
- pH probe
- Temperature Probe
- Computer
- Timer

Task 4:


1. Firstly, take one beaker and fill it with 50ml of coke.

2. Then take the solid Alka Seltzer tablet and place it in the coke, as soon as it is placed in the coke make sure to start the timer.

3. Once the timer has reached 30 seconds then take the pH probe and place it in the beaker. Take down the results of the pH probe after 10 seconds.

4. Once you have taken the pH probe out of the beaker then place the temperature probe into it. Take down the results of the temperature probe after 10 seconds.

5. Once all the results have been taken down for the beaker with coke and a solid Alka Seltzer tablet then repeat the steps but with the crushed Alka Seltzer tablet.

6. Make sure and take down the results of the crushed Alka Seltzer tablet at the same times as the solid Alka Seltzer tablet.

7. Gather all the results and compare the differences to your hypothesis you wrote.

Task 5:

Safety Procedures:
1. Make sure to wear goggles because you do not know what chemical reactions may occur.

2. DO NOT taste or smell any of the materials used in this experiment before or after.

3. Make sure your working space around you is clear before you conduct this experiment.

4. If you have a problem be sure to ask your teacher for help instead of trying to deal with it on your own.

5. Try to prevent the beakers from being close to the edge of a table.

.Task 1: Predication
I am predicting that the pH will increase due to the fact that the Alka Seltzer would be a base and the acids in cola would decrease while the pH increase, because as a acid decrease the pH goes up. Also the temperature would change to a cooler form than before.
Task 2:
Independent variables:
· Alka Seltzer
Dependent variables:
· pH
· Temperature
Factors to be changed:
1. Make sure both of the colas have not been shaken.
2. Make sure both of colas have not been in the refrigerator.
3. Each cola should not have been open before the experiment.
4. Make sure each of the colas has the same amount of liquid in the container.
5. Make sure the cola is from the same brand.

If I have a coca cola, whole Alka seltzer and a crushed Alka Seltzer, then I believe that the crush Alka Seltzer will increased more than the whole Alka Seltzer in the pH scale. This is because the crushed Alka Seltzer will not have to take as much time to dissolve in the cola which increases in the pH.
Task 3: Materials –
· Coca cola
· Two (2) 100 ml beakers
· 400 ml beaker
· Two (2) Alka Seltzer
· Computer
· pH rode
· Data logger
· Timer
· Temperature robe
· Water
· Tissue paper

Task 4: Procedure:
1. Make sure you have all your supplies set up before proceeding.
2. Connect the data logger into your computer; also connect the temperature and pH probe into the senor.
3. Place two (2) 100ml beakers and a 400ml beaker on the table. Pour sixty milliliters (60 ml) of coca cola into one beaker first.
4. Then drop either one of the whole or crush tablets into the beaker with the coca cola. Then click the “collect” button and place the pH or temperature probe into the beaker for 60 seconds.
5. After pull out the probe out of the beaker and wash the probes after using them.
6. Collect the data you have received from the experiment onto a table and take notes.
7. Now repeat from step four to six (4-6) and analyze your results and what you have observed. Repeat step 4 with the probe you did not use before.

Task 5: Safety and Precaution
Be sure to wear safety goggles and gloves while doing your experiment. DO NOT consume any of the Alka Seltzers. Make sure your utensils are clean and wash the probes after using them in each beaker.
Task 7: Results

external image clip_image002.gif

The coca cola when mixed with the Alka Seltzer seemed to have changed in its pH and temperature, but the pH and temperature was different from it’s original state due to the fact that one tablet was broken and the other a whole. The variables were the whole and broken Alka Seltzer tablets that were being compared in the experiment. When the whole Alka Seltzer tablet was dropped into the coca cola, the tablet took at least a few minutes to finish dissolve in the cola. It didn’t react to the coca cola at once like the broken tablet and did not have as much of a effect in the pH but better in temperature than of the broken tablet.
By the graph above it shows that coca cola before being mixed with the Alka Seltzer was pH 2.73* and Temperature 30.3*. Then after being mixed with the Whole tablet, its pH dropped to almost of neutral state and cooler than before. The pH after was 6.40* and temperature 28.7*. I think this is so because the whole tablet acted as a base to do as it should and lower the acids in the coca cola which cooled the coca cola down. When the broken tablet was mixed with the cola, as I said before the coca cola instantly when in contact with the cola begun to fuzz and bubble over the beaker. The pH after in contact with the cola was 6.33* and temperature 29.5. This shows that the broken tablet did the same as the whole tablet but faster and changed the pH by 3.60* and temperature by 0.8*. Therefore when comparing the variables, the broken Alka Seltzer changed the coca cola pH into more of a neutral but the Whole tablet’s temperature was cooler. The difference in pH between the whole and broken tablet was 0.07 which isn’t much but still a change. And the temperature is 0.8 of a difference.
Task 8: Conclusion
By my results it shows that if I have a coca cola, whole Alka seltzer and a crushed Alka Seltzer, then the thought process would be that the crush Alka Seltzer will increased more than the whole Alka Seltzer in the pH scale making it more neutral than acidic. This is because the crushed Alka Seltzer will not have to take as much time to dissolve in the cola which increases in the pH. Then I wondered by the difference in temperature and pH, why the broken Alka Seltzer tablet was hotter than the whole tablet? I predict this is so because the broken Alka Seltzer tablet didn’t have much time to cool the temperature of the coca cola due to the fact that it dissolved quickly, unlike the whole Alka Seltzer which took longer and was the cooler of the two.

Joe Task 1
pH will increase
Temperature will stay the same

Task 2
Independent Variable: the amount of Alka Seltzer
Dependent Variable: the pH and/or the temperature
Factors to be controlled: environment temperature
Hypothesis: If the Alka Seltzer are put into the cola, then the pH will increase

Task 3
Temperature probe
pH sensor
Data Table
Recording Materials (pen, paper, etc)
Alka Seltzer tablet (solid)
Alka Seltzer tablet (crushed)
Some cups or beakers for the coke

Task 4
1. Record the pH and temperature of the cola before the experiment starts. To control the temperature, the cola should be the same temperature as the environment’s temperature.

2. Put the solid tablet in one cup of coke and let it dissolve. Then record its pH and temperature.

3. Put the crushed tablet in another cup of coke and let it dissolve. Then record its pH and temperature.

4. Compare results.

Task 5__
1. Keep your computer clear of any liquids.

2. Keep cups/beakers away from edges to prevent them from spilling/breaking.

3. Don’t eat the Alka Seltzer tablets.