The more concentrated the chemical, the more collisions there will be between particles. This is because there are more acid particles in the same volume so therefore particles will tend to collide more quickly and easily with particles on the surface.
Another factor that can alter the rate of reaction, using the collision theory is the effect of surface area. This is done by using smaller pieces of solids, especially powders, as these react faster than larger pieces. This is because more particles are exposed over a larger surface area.
The effect of temperature also has an affect on the rate of reaction. When we heat particles they have more energy ands so they tend to move around more vigorously. As particles travel around faster because there is a larger proportion of colliding molecules with the minimum activation enthalpy needed to react.
A catalyst is also used t speed up reactions, and at the end of the reaction the catalyst is chemically unchanged.
For my investigation, I have chosen to change the concentration of the acid in my experiment and to measure the time taken for the chemical reaction to fully take place.
How will concentration affect the rate of reaction?
What I am going to keep the same…
Surface area of Ant Acid
Volume of acid solution
Temperature
Apparatus…
Hydrochloric Acid
Ant Acid Tablet
Measuring cylinder
Beaker
Apron
Safety Glasses To perform a safe experiment
Stopwatch
Prediction
I think that when we change the concentration of the acid to a stronger concentration, the rate of reaction will increase. This is because the concentration of acid consists of more molecules in the same volume so more collisions will be taking place per second. I predict that the ant acid tablet in the all acid solution (10cm3) will react a lot faster than any of the other experiments, as all the other solutions will be diluted with water and so it will be less concentrated. As each concentration decreases so will the rate of reaction as less collisions are taking place, so therefore the ant acid will take longer to react.
Diagram of what I think will happen...
I expect more collisions to take place in the more concentrated acid.
Obtaining Evidence
I tested ant acid in 10cm3 of acid and found that each of the outcomes of the three tests I did were very closely related.
Diagram of my Experiment
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Results
My Test Results
After I had obtained my results for my experiment I then gathered other results of different concentrations obtained by the rest of the group. The concentrations tested were:
10cm³ acid
8cm³ acid, 2cm³ water
6cm³ acid, 4cm³ water
4cm³ acid, 6cm³ water
2cm³ acid, 8cm³ water
The group results are as shown below:
From looking at my results graph above I have found that the there is a faster rate of reaction in 10cm³ acid than there is in dilute acid.
Evidence and Evaluating
When we changed the concentration of the acid to a dilute solution the rate of reaction decreased. Looking at the group results the averages show us that each time the solutions got weaker the rate of reaction also got slower. In the test with 10cm³ acid, the reactant reacted quickly. This was because there were enough hydrochloric acid molecules to collide with the particles of the ant acid tablet. Whereas with the weaker solutions, for example, 2cm³ acid, 8cm³ water, it took a lot longer to react. This is because there were not enough molecules in the hydrochloric acid to react with those of the ant acid tablet. This was because there was not enough kinetic energy or enough concentration for the acid to react with the tablet, therefore there was less collisions taking place per second.
My prediction was correct as I predicted that the most concentrated solution would have the most collisions per second taking place.
There were no unusual readings within this experiment.
To improve my experiment I would test again by measuring the time taken for ant acid to react using surface area as a variable. To do this I shall compare time taken against the size of ant acid tablet, e.g.: powder, small pieces, larger pieces, whole tablet. I shall use the same amount of acid in each experiment. I would then compare and evaluate my results. In this experiment I expect powdered ant acid to react very quickly due to the tiny particles covering a larger surface area and therefore colliding with more particles of the hydrochloric acid.
I think my investigation was carried out fairly well overall.
