Based on what you’ve learned in this portfolio, describe how you could set up an experiment to investigate the effect of particle size on reaction rate. Your experiment should use antacid tablets and other materials that you used in previous investigations. What would you expect to happen?

Answer 1

To investigate the effect of particle size on the reaction rate of antacid tablets, we can design a simple experiment following these steps:

Materials Needed:

• Antacid tablets
• Mortar and pestle (or a suitable grinder)
• Water
• Beakers or clear cups
• Stopwatch
• Thermometer
• Scale (for measuring the mass of the antacid tablets)
• Stirring rod or spoon

Experimental Setup:

1. Preparation of Different Particle Sizes:

   • Use whole antacid tablets, crushed tablets that are finely ground, and tablets that have been coarsely crushed (using the mortar and pestle).
   • Aim for three different particle sizes: whole, coarse, and fine.
   • Record the mass of each powdered sample for consistency and accurate measurements.

2. Measuring Reaction Rate:

   • Prepare a fixed volume of water (e.g., 100 mL) in separate beakers for each trial.
   • Measure the temperature of the water and ensure it is consistent across all trials to account for temperature effects.
   • Start by adding a known mass of the whole tablet to the water at a specific starting time, stirring gently, and using the stopwatch to time how long it takes for the tablet to completely dissolve.
   • Repeat this step for the coarsely crushed and finely powdered tablets while maintaining the same volume of water and ambient conditions.

3. Observations:

   • Record the time taken for each sample (whole, coarse, fine) to fully dissolve.
   • Note any observable changes, such as the rate of bubbling or gas release, which indicates a reaction is occurring.

4. Replicates:

   • Conduct multiple trials for each particle size (at least 3 replicates) to ensure reliable results.

Expected Results:

Based on the principles of reaction kinetics, we would expect the following outcomes:

• Whole Tablets: The reaction rate will be slow, as the surface area exposed to the water is limited. The large particle size means that there are fewer opportunities for the acid (from the stomach, in a real-world application) to react with the tablet.

• Coarse Tablets: The reaction rate will be faster than the whole tablets but slower than the finely powdered form. The increased surface area from partial crushing allows for more interaction with the water compared to the whole tablets.

• Fine Powder: The reaction rate will be the fastest as the finely ground antacid has the largest surface area, allowing for maximum exposure and interaction with the water, leading to quicker dissolution.

Conclusion:

This experiment would effectively demonstrate the relationship between particle size and reaction rate. It is expected that smaller particle sizes lead to faster reaction rates due to the increased surface area available for reactant interactions. Analyzing the collected data should reveal a clear trend that supports this hypothesis.