SAFETY: In this experiment there were not many safety procedures that I had to follow. But because we were using chemicals we had to make sure that any spillages were reported to the teachers and also if there were any breakages of glass. We also were goggles in case of any spillages so that no solution would go into our eyes. We also had to follow all the laboratory rules and make sure that any obstructions on the floor would be cleared a way such as bags. Whilst doing this experiment I would also have to know where the paper towels are, in case of a spillage. We also had to make sure that once we had used the hydrogen peroxide we replaced the lid on the bottle because it was a chemical.
Method:
- Firstly we will get all the apparatus which is listed in the apparatus list
- Once we have collected all the equipment will then set it up so that the experiment is ready to carry out.
- We will then weigh the catalyst to the correct amount which will be 0.1g. To get the correct weight of the catalyst we will be using some scales to weigh each amount.
- We will then need to collect the correct amount of hydrogen peroxide, and distilled water to make the desired concentration. In the table below I will show how to make the correct concentration.
- Once we have figured out what concentration we want and how to get it we will put the catalyst in the conical flask. We will then put the hydrogen peroxide in the conical flask and as quickly as possible we will put the bung on the conical flask.
- As soon as the hydrogen peroxide has been put in the conical flask then we will start the stop clock. When 30 cm3 has been displaced then we will stop the clock.
- Once the experiment has finished we will record the time it took on to a table, and from that we will be able to work the average time.
Prediction: Using scientific knowledge I can predict several things. The first being that I believe in 0% concentration nothing will happen because the is no hydrogen peroxide to react with, therefore the hydrogen peroxide will not be able to displace the catalyst. Because I think this I am able to predict that the fastest reaction will be with 100%, I can back this up with scientific knowledge by saying that because it is a higher concentration then, there will be less molecules for the catalyst to react with causing the reaction to take place quicker because there will be more collisions. I will also explain this by using a diagram below. The first diagram will be for the reaction at 0%, the next at 50% and the last at 100%. The white dots will represent catalyst molecules and the black will be the hydrogen peroxide molecules.
This diagram represents what will happen when the catalyst is mixed with water. As you can see because there is no hydrogen peroxide molecules the water molecules have nothing to collide with there fore no reaction can take place.
This shows the reaction happening with 25% concentration. As you can see because there are some hydrogen peroxide molecules then there is something for the catalyst to collide with therefore a reaction will occur?
This diagram represents the reaction with 100% concentration. It shows that there are more molecules than 50%. Because there are more molecules the reaction will happen quickest at this concentration.
Preliminary Work: Before we done our original experiment we had to do another experiment. This gave us some idea of what our results were going to be like. The point of the experiment was to see what we were going to do in the final experiment, e.g. If we were using too much catalyst. We found out from doing our first experiment that seeing how the concentration affects the rate of reaction was better than changing the mass of the catalyst because, some times it was to quick to record the time.
Results of final experiment: The table below will show the results of our experiment using 0.1g of catalyst and 20ml of hydrogen peroxide.
Analysis: By looking at my results table which is above and my graph I can see that the whole experiment went very well and that there were no anomalies. I was also able to spot a trend, which was the higher the concentration the quicker the reaction will happen. This was what I predicted in my prediction. Whilst we were working out our average time we used the times from each repeat because there were no anomalies that we had to miss out. The reason I think why the hydrogen peroxide with a concentration of 100% was quicker than the 0% concentration, was because it was 100% and it had a lot more molecules for the catalyst to collide causing the reaction to happen quicker, and the 0% was just distilled water there was nothing for the catalyst to react with so no collisions occurred.
Conclusion: I saw a pattern from my results which was the more concentrated the hydrogen peroxide, the quicker the rate of reaction. This is what I said in my prediction. This is because more concentrated solutions of Hydrogen peroxide have more hydrogen peroxide molecules. Because there are more molecules, more collisions occur between these and the catalyst, manganese oxide. This produces more reactions than in a lower concentration in a certain amount of time. A collision is just that, because of kinetic energy, molecules move around in liquids and gases. As the molecules move they collide.
Evaluation: I think that my experiment went very well. There were no anomalies, and there were no accidents whilst the experiment was being carried out. Like in most experiment there were several things we could have improved on. The first being the most obvious, by the time the bung has been put on the conical flask the reaction will of already started this would of meant that our recordings were not entirely accurate. But I don not know of any ideas to solving this problem. I also think that the measuring devices could be improved because the scales were not very accurate. The other in accurate part of the experiment knew when the reaction had displaced 30cm3 of air because it was difficult to read off the burette.