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The particle size of a substance is how large or small the particles of that substance are. We can change the size of particles in a solid in different ways:
Cutting it with a knife or scissors.
Powdering it with a mortar and pestle.
Dissolving it in Water.
All these methods will DECREASE the particles size (make the particles smaller)
When the particles are smaller in size their surface area is greater.
Therefore as the particle size decreases, the surface area increases.
The experiment below demonstrates the concept that when smaller particles are used in a reaction the rate of the reaction is faster.
In this example the reaction is between marble chips (calcium carbonate) and hydrochloric acid. The gas produced (carbon dioxide) can be collected as shown.
The faster rate of reaction the less time it will take produce the same volume of gas.
When a large piece of marble is made into pieces, the surface area increases. When the particles are smaller the chemical reaction takes place faster.
The smaller the particles are the higher the rate of particles colliding with one another and the higher the chance of successful collisions.
In a reaction the rate is most rapid at the beginning
It is possible to measure the gas produced at regular time intervals in experiments like the one shown above and this information can be used to plot a graph.
Below are the results of another experiment carried out using large and small marble chips reacting with hydrochloric acid. You should be able to plot these results as a line graph . An example of what the graph should look like is shown below the results table.
Notice if the same quantity of reactants is used in each experiment then the volume of gas produced is the same in both experiments, it is just produced more quickly in the experiment using small marble pieces (the red line).
The time in minutes is on the x axis because it is the independent variable. The dependent variable (volume of gas) is on the y axis.
Decreasing the particle size of reactant increases the rate of a reaction.
Decreasing the particle size of reactant increases the rate of a reaction.
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