Effect of Particle Size on Reaction Rate

• As you observed, in this reaction also, decreasing particle size decreases the time taken for the reaction to complete
• This means that the rate of reaction increased as we chopped up the tablet of the same mass

• In order for reactants to react, they must collide.
• If there are more frequent and successful collisions, the rate of reaction is increased.
• Increasing the particle size exposes greater surface area to the other reactant.
• This means that there will be more collisions between the two reactants, which increases the rate of the reaction

Another Experiment

• In order to increase reliability of the statement that "Increased surface area increases rate of reaction", another experiment was carried out.
• In this experiment, reaction between Calcium Carbonate and Ascorbic acid (and acetic acid) was observed
• Vitamin C tablet was used as a source of calcium carbonate and ascorbic acid
• Vinegar was used as a source of acetic acid
• For every sample used:

mass of Vitamin C tablet - 8 g

volume of vinegar - 100 ml

• Again, time for effervescence to complete was measured
• The effervescence was due to the carbon dioxide produced in the reaction
• The basic equation for the reaction are:

calcium carbonate+ascorbic acid --> calcium ascorbate+carbon dioxide+ water

calcium carbonate+acetic acid --> calcium acetate+carbon dioxide+ water

Results

The following table shows the results of the experiment

min

Chalk and Vinegar Experiment

Decreasing particle size

For every sample:

Mass of chalk used - 10 g

Volume of vinegar used - 100 ml

The following video shows the equipment and procedure for the experiment

The following graph summarizes the results

Video showing equipment and procedure

As the particle size decreased, there is a decrease in the time for effervescence to complete, thus there is a decrease in the time taken for completion of reaction.

This means that the rate of the reaction increases as the surface area of the chalk increases.

Results

The following table shows the results of the reaction

Results

The following graph summarizes the results

Explanation

Decreasing particle size

Introduction

• Changing the size of particles of reactants in a chemical reaction will change the rate of the reaction
• Increasing particle size will reduce the surface area and reduce the rate of the reaction
• Decreasing the particle size will increase surface area and increase the rate of the reaction
• It must be noted that the mass of the particles must remain the same during observation, so valid results are obtained

Experiment 1

Comparing the results

• In this experiment, reaction between calcium carbonate and acetic acid is used
• Chalk was used as a source of calcium carbonate
• Vinegar was used as a source of acetic acid
• Effervescence was due to the carbon dioxide produced in the reaction
• Time for effervescence was measured because this marks the end of the reaction
• The basic equation for the reaction is

We can compare the graphs of the two experiments

As you can see, both results follow a similar pattern

Effect of Particle Size on Reaction Rate