Prediction
I think that as the concentration of hydrogen peroxide increases, the rate of reaction will increase and as the concentration decreases, the rate will decrease. I think this because with a higher concentration, there will be more molecules to collide, so there will be more collision, so the reaction will occur faster. With a lower concentration, there will be fewer molecules, so less collisions and the reaction will occur slower.
However, Hydrogen Peroxide decomposes very slowly without a catalyst. A catalyst is a substance that speeds up a reaction without being used itself. This is because Hydrogen Peroxide can’t get over one barrier - activation energy. The catalyst for Hydrogen Peroxide Decomposition is Manganese (IV) Oxide. The best way to visualise activation energy is to imagine a hill with a road over it. The car with the weak engine can’t make it over the hill, but the car with a catalysed engine can. Catalysts lower the activation energy needed for the substance to react. This can be shown in a simple graph:
The catalyst lowers the activation energy, allowing the reaction to take place. In our investigation, we will not vary the amount of catalyst we use.
Safety
To ensure our safety in this experiment, we will clear all spillages and be careful with Hydrogen Peroxide, as it is corrosive.
Preliminary Work
To test whether our experiment was going to work we performed a preliminary experiment. Here is our results table
Our preliminary results show our method works.
Results
Graph
See attached graph paper
Conclusion
In this experiment, we found that hydrogen peroxide break down was best with a higher concentration. This happens because there were more particles to collide at higher concentrations than at lower concentrations. As you go down the concentration gradient, the rate of reaction decreases. These diagrams best show it:
As there are more molecules in the left-hand diagram, there are more collisions, so more reactions happen. However, in the right-hand diagram, there are very few molecules, so fewer collisions occur, so fewer reactions occur. My results support my conclusion. The higher concentration did react quicker. The 50% concentration reacted very quickly and the 12.5% reacted slowly. The 0% didn’t react because there were no Hydrogen Peroxide molecules to react.
Evaluation
Our method was not very good. Our results were quite good but we had 3 anomalies. To improve our procedure we could find a way to stop oxygen escaping before we put the bung in. If I had more time, I would test more concentrations to see whether the conclusion is right. I would also not do the 0%, as it is pointless, as no reaction was going to take place. We could improve the accuracy of our results by electronically stopping the clock after 40 ml has been given because it was difficult to see with the higher concentrations when it had reached 40 ml and this affected our results.
