Can you change the rate of a chemical reaction by changing the particle size of the reactants?

Question: This question came from a 13 yr old student.
Answer: The answer to her question is yes.  Many chemical reactions will increase proportionally to the surface area of the particle.   The more surface exposed, the faster the reaction can occur.  
An example that comes to mind;   mixing Alka Seltzer with water creates a chemical reaction that creates water, carbon dioxide gas and a salt.  If you drop two large Alka Seltzer tablets in the water, the reaction will take place at a certain rate.   If you then cut the size of the tablets in half, it will occur faster; cut them in quarters, even faster.   She could do something along these lines by timing how long it takes for the fizzing to stop with increasingly smaller particles.  I’m sure there are other possibilities as well; baking soda and vinegar, etc.
Michelle Carlson, PhD
Microbiologist

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