So my prediction is: a higher concentration in the acid means there are acid particles to collide and react with the magnesium particles.
I will begin with: And finish with:
Magnesium + Sulphuric Acid Hydrogen + Magnesium Sulphate
This is what I predict the graph I plot will look like:
Hydrogen (cm )
Time (sec)
Method
In my experiment I will have to change one variable. The variable that I have chosen is the concentration. So I will have to change the concentration for each test to see how it affects the rate of reaction. I will have to keep everything else the same, for example:
- Temperature
- Surface Area
- No catalysts
- Amount of time between each recording
To keep my experiment fair I will not change the time difference between each recording. I will not change the temperature of the water, and I will always put in the same amount of magnesium in each time. Also I wont tamper with the equipment in the experiment i.e. I will not shake the conical flask whilst the reaction is taking place as this will increase the particle movement and I wont let oxygen into the measuring cylinder whilst the hydrogen is being released into it.
I will have to keep my experiment safe so I will make sure I am wearing goggles at all time because the acid is very dangerous. I will also make sure that I clear up any spillages as somebody could slip and fall.
Here is my list of apparatus I will need for my experiment:
- Measuring cylinder
- Goggles
- Stopwatch
- Conical Flask
- Delivery tube
- Magnesium
- Sulphuric Acid
- Small measuring cylinders
In our experiment we will be measuring the amount of hydrogen produced, some of the ways we could measure the output of gas by measuring the weight. But in our experiment we will be collecting the hydrogen in a measuring cylinder and finding out the volume. Here is what we are going to do.
The first thing I will do in my experiment is fill a large washing up bowl so its half full with water. Then fill the large measuring cylinder to the top with more water. Then we placed the measuring cylinder with water in upside down in the bowl, making sure we don’t lose and water when we do it. Then we get a piece of Magnesium 3 centimetres long and place it in the conical flask. Measuring out the required amount of water we pour that into the conical flask followed by the required amount of acid. Then we put on the lid of the conical flask, and place the delivery tube so it runs from the conical flask into the large measuring cylinder and start the stopwatch.
We will record the amount of hydrogen collected in the large measuring cylinder every 15 seconds, we will do this for 75 seconds; we will then record all of the results in a table. We will conduct this experiment twice, record the results and then display them in a graph. Once we have done that we will average our results and turn plot them onto a graph also.
Here is the amount of Acid to the amount of Water:
Here is a scientific diagram of my experiment:
My Results
Volume of hydrogen produced (cm )
My Second Set of Results
Volume of Hydrogen Produced (cm )
Conclusion
From my practical work I have found out that the higher the concentration of a substance the faster a reaction occurs. So because there is a higher concentration there are more acid particles available to collide with the magnesium particles causing a reaction and because there are more particles the reaction occurs faster.
In our experiment we had to dilute the acid to make the experiment work. We used water to dilute the acid and we found that when there was much more water than acid the reaction was a very small one and it was also very slow. We managed to get a reaction after 60 seconds and before that nothing happened. When the amount of acid was almost as much as the amount of water the reaction occurred much faster but there was still not very much of a reaction, the final amount of hydrogen recorded was only 10cm .
When there was 20cm of acid and only 5cm of water there was a noticeable difference. There was 6cm of hydrogen produced in just 15 seconds and the final amount of hydrogen recorded for that one was 18cm . The results for pure acid were continuous and a reaction was seen almost immediately. All of my results prove that when there is more acid in the conical flask than water the reaction occurs much faster and more hydrogen is collected. So the higher the concentration of a substance the quicker the particles collide and react.
My Evaluation
I had to make sure my results were reliable so that’s why I did two identical tests. This ensured that my results were accurate and proved that the higher the concentration of a substance the faster a reaction takes place. Doing two tests means that if I had made any mistakes in the first test then I would have realised after doing the second one.
Some readings were slightly hard to record accurately as it was hard to put the acid and the water in the conical flask and start the stopwatch all at the same time. Also we had to add our acid and water to the magnesium just after each other because we couldn’t put them in at the same time. This means that we would have started some sort of reaction before the other substance was added and before the stopwatch had began timing. This would have given us a slightly false recording. Another accuracy problem was that the measuring cylinder’s markings were fading so it was sometimes hard to read off the numbers on time. Another problem was when I called out for the volume of gas to be recorded it took a while for my partner to read the number on the cylinder and read it out so I could write it down. This means there is some inaccuracy in our results. Sometimes there is already air in the measuring cylinder when we begin the test this means that we would count that air as well as the hydrogen produced.
If we had more time to improve our experiment so we could improve our accuracy, we would put in the acid and water in the conical flask and start the stopwatch all at the same time. I would also take time to find an accurate measuring cylinder with clear markings so the volume of gas could be measured quickly. To prevent air leaking into the measuring cylinder before the test has already begun, I will have to keep trying to put I the cylinder without air entering until I get it perfect.
I don’t really have any anomalous results, except on the first test for 20cm of acid and 5cm of water I have one slightly unusual result. At 60 seconds the volume of hydrogen is only 14 which is not really continuing on with the pattern on that set of results.