AQA GCSE FOUNDATION Chemistry: Investigating Reaction Rates with Surface Area

Investigating Reaction Rates: The Effect of Surface Area

This experiment explores the relationship between the surface area of a reactant and the rate of a chemical reaction. We'll use marble chips (calcium carbonate) reacting with hydrochloric acid to produce carbon dioxide gas. By varying the size of the marble chips, we can observe the effect on the reaction rate.

Materials:

• Marble chips of different sizes (e.g., large, medium, small)
• Hydrochloric acid (dilute)
• Measuring cylinder
• Gas syringe or a graduated cylinder with a delivery tube
• Stopwatch
• Beakers

Procedure:

1. Set up:
   • Fill the measuring cylinder with a known volume of hydrochloric acid (e.g., 50 ml).
   • Connect the measuring cylinder to the gas syringe or graduated cylinder using the delivery tube.
2. Experiment:
   • For each size of marble chip, follow these steps:
     • Step 1: Place one marble chip in the hydrochloric acid.
     • Step 2: Start the stopwatch immediately.
     • Step 3: Record the volume of gas produced every 10 seconds for 1 minute.
3. Repeat steps 2 for each size of marble chip.

Data Analysis:

1. Plot a graph: Plot the volume of gas produced against time for each size of marble chip. This will show the rate of gas production for each chip size.
2. Compare the graphs: Analyze the graphs to determine how the size of the marble chip affects the rate of the reaction.

Observations and Explanations:

• You should observe that the smaller the marble chips, the faster the reaction rate. This means more gas is produced in the same amount of time.
• Collision theory explains this observation. Smaller chips have a greater surface area exposed to the acid. This leads to more frequent collisions between the reactant particles (calcium carbonate and hydrochloric acid), increasing the likelihood of successful collisions and faster reaction rates.

Safety Precautions:

• Wear safety goggles to protect your eyes from splashes.
• Handle hydrochloric acid with care, as it is corrosive.
• Work in a well-ventilated area.

Further Investigations:

• Investigate the effect of temperature on the reaction rate, keeping the surface area constant.
• Explore the effect of using a catalyst on the reaction rate.
• Conduct similar experiments with other reactions, such as the reaction of magnesium with hydrochloric acid.

Conclusion:

This experiment demonstrates the relationship between surface area and reaction rate. By increasing the surface area of a reactant, the rate of the reaction increases due to more frequent and successful collisions between reactant particles. This understanding is fundamental in various chemical processes, from industrial production to biological systems.