Question

To investigate concentration versus reaction rate, you will need the remaining materials, which you should already have set aside from Part 1. Gather your materials and review the items. Specifically, you should ensure you have the following materials:
• the materials you used in the activity from Part 1
o clear 12-ounce plastic cups (4)
o fresh antacid tablets from your package (at least 4)
o marking pen
o measuring cup (optional)
o pen or pencil
o sheet of graph paper
o stopwatch or a watch or clock with a second hand
o tap water
Step 1: Plan and Conduct Experiment
Plan and Write Your Procedure
Now, you will create a step-by-step procedure for the second experiment. Review the procedure from Part 1 to understand how to describe the data and the collection methods you will use. You should be as detailed as possible.
In this experiment, you need to decide what evidence and facts you need to collect. It may help you to think about the scientific principles. Answer the following questions and write out your procedure. (Add additional space as needed for any item.)
1. What evidence and facts do you need to collect?
2. What are the independent and dependent variables? Remember that data you collect is the dependent variable.
3. How will you measure the reactant concentration? It’s important to think about this now because you will graph your data.
4. What are the steps in your procedure? Describe them.
Record Data and Notes
Now, you will conduct your experiment and record your data. You can record your data with any method you choose, but the table in Part 1 is provided for you as a starting point. You may need to update the heading columns. If you notice anything during your investigation you want to document, you can also use this space to jot down any notes or additional observations. (Add additional space as needed.)

Answer 1

Below is a complete plan and procedure you can use for Part 2: investigating how concentration affects reaction rate with the antacid tablets and water. I include answers to the four planning questions, a clear step-by-step procedure, a data table template you can copy, and a few notes about safety, repeats, and how to graph your results.

1) What evidence and facts to collect
- The time (in seconds) it takes for the antacid dose to finish reacting (tablet fully dissolved / fizzing stops) for each concentration.
- Any qualitative observations (amount of fizzing, bubbles, foam, pieces left, temperature changes, unusual behavior).
- Repeat times for each concentration so you can compute an average and spread (precision).

2) Independent and dependent variables
- Independent variable: reactant concentration (amount of antacid per fixed volume of water). You will change this (different fractions/number of tablets per cup).
- Dependent variable: reaction rate, which you will measure by the time required for the tablet to completely dissolve (you can convert to a rate as 1/time if you prefer).
- Control variables to keep the same: water volume in each cup, water temperature, cup type, tablet brand/age, whether you stir or not, and the way you start/stop the stopwatch.

3) How to measure reactant concentration
- Use a fixed volume of water in every cup (e.g., 200 mL). Express concentration as “tablets per 200 mL” (or as fraction of a tablet per 200 mL). Example concentrations: 0.25 tablet / 200 mL, 0.5 / 200 mL, 1.0 / 200 mL, 2.0 / 200 mL.
- If you want concentration in a standard unit, convert to tablets per liter: concentration (tablets/L) = (tablets per 200 mL) × 5.
- If you can crush tablets evenly, that improves consistency when using fractions (e.g., quarter tablet). If you cannot crush, use whole and half tablets only.

4) Step-by-step procedure
Materials: 4 clear 12-oz plastic cups, at least 4 fresh antacid tablets, marking pen, measuring cup (for 200 mL), stopwatch/clock with second hand, pen/pencil, graph paper, tap water.

Procedure:
1. Label four cups A, B, C, D with the marking pen.
2. Measure and pour the same volume of tap water into each cup. Example: 200 mL into each (use the measuring cup). Record the water temperature (room temperature).
3. Decide concentrations to test. Example plan:
- Cup A: 0.25 tablet in 200 mL
- Cup B: 0.5 tablet in 200 mL
- Cup C: 1.0 tablet in 200 mL
- Cup D: 2.0 tablets in 200 mL
(Adjust values as desired; make sure you have enough tablets.)
4. Prepare tablet portions. If you use fractions (¼, ½), crush tablets and divide evenly or break along scored lines if available. Put prepared portions on clean paper, labeled for each cup.
5. Set up stopwatch(s) and data table. Plan to perform at least three trials for each concentration (remove and replace fresh water and fresh tablet each trial).
6. For Trial 1 of Cup A:
a. Place Cup A on a level surface. Confirm water temperature.
b. Drop the designated tablet portion into the water and start the stopwatch immediately as the tablet touches the water.
c. Watch the cup without stirring. Stop the stopwatch when the tablet has completely dissolved or fizzing/bubbling visibly stops and no solid pieces remain. Record the time in seconds. Note any observations (e.g., vigorous fizzing, foam).
7. Clean and dry Cup A (or use a fresh cup) and refill with the same volume and temperature of water for Trial 2 and Trial 3. Repeat steps 6a–6c for all three trials.
8. Repeat steps 6–7 for Cups B, C, and D (all concentrations), recording three trial times each.
9. Calculate for each concentration:
- Average time = (sum of 3 trial times) / 3
- Reaction rate = 1 / (average time) (units s^-1) or another proportional rate (e.g., relative rate compared to lowest concentration).
10. Prepare a graph: x-axis = concentration (tablets per 200 mL), y-axis = reaction rate (1/average time, s^-1). Plot the average for each concentration with error bars if you like (use standard deviation). Fit a line or curve and describe the trend.
11. Clean up: dispose of solution down the sink with running water, wash cups if reusing, and wash hands.

Data table template (you can copy this):

Concentration (tablets per 200 mL) | Amount added (tablet) | Trial 1 time (s) | Trial 2 time (s) | Trial 3 time (s) | Average time (s) | Reaction rate (1/s) | Observations
-----------------------------------|-----------------------|------------------|------------------|------------------|------------------|---------------------|-------------
0.25 | 0.25 | | | | | |
0.50 | 0.5 | | | | | |
1.00 | 1.0 | | | | | |
2.00 | 2.0 | | | | | |

Notes and tips
- Repeat each condition at least three times for reliability. If results vary a lot, do more repeats or check for uncontrolled variables (temperature, tablet size differences).
- Keep everything at the same temperature. Cooler water slows dissolution; warmer speeds it up.
- Do not stir unless you decide to make stirring a controlled variable (i.e., stir for the same time and speed each trial). If you stir, standardize the method.
- Use fresh tablets from the same package to minimize composition differences.
- If you can finely crush and weigh tablets (if a balance is available), you can measure mass per volume, which will give a true concentration in g/L.
- When graphing: if reaction rate is proportional to concentration you should see a roughly straight line through the origin. If you plot average time vs concentration, you will see a decrease/increase depending on which you choose to graph.
- Safety: don’t ingest tablet pieces or the reaction water. Clean up spills promptly.

If you want, I can:
- Provide a ready-to-print data sheet formatted for your lab table.
- Suggest specific concentration values based on how many tablets you have.
- Show an example graph and how to calculate slope and uncertainty from your data.