For the concentration experiment, I will dilute the Hydrochloric acid to the appropriate measurement; I will use 11 different concentrations of the acid. After this, I will add the crushed marble (I am going to crush the marble so that the surface area stays the same) before putting the bung into the flask. Then the stopwatch is to be set, and the amount of gas released in 10 seconds is recorded.
To make this a fair test, I am going to do each test for each experiment 3 times, add the 3 results together, and divide them by 3. I will do this to get the average, so that any odd results (‘glitches’ in the experiment) wont overtake the accurate results. I have ground the marble up into a fine powder so that getting the right amount each time (1 gram) will be easier, and the surface area will be the same. This is important, as the more surface area there is, the more chance of a reaction. This is because a reaction happens when two particles collide. I am also going to fill the measuring cylinder up with water, and the tube leading from the bung in the flask is to be put in the measuring cylinder at all times. The bung is to be inserted into the flask as soon as the marble is poured into the acid.
I think that the less concentrated the acid is, the slower the reaction will take place. This is because there are fewer particles for the powder to react with, so the reaction will take longer; the particles need to collide, crash together to make a reaction, as they move randomly around the solution. The more collisions that the particles have, the faster the reaction is. This is called the collision theory. Higher concentrated has a faster reaction occurring, as there are more particles in the same volume, leading to a greater chance of the particles colliding.
In this experiment, the acid will react with the surface of the marble. As I am using crushed marble, the surface area (this is the outside layer of marble) is larger, therefore this will take less time than if I was using a block of marble.
I found that there were no extreme odd results, but the 1st try didn’t match as well as the 2nd and 3rd. On the average graph, a negative correlation is shown; the downward graph gets steeper and steeper. This tells me that the gas is released at a slower pace when less acid is used for the concentration experiment. This proves my prediction was correct this investigation.
Problems I found whilst doing the experiment were that the gas was escaping before the bung could be put onto the flask. To solve this problem, there could have been 3 people at the ready, one of them could’ve said they were ready, and poured the marble powder into the hydrochloric acid, while the other one quickly put the bung in and said to the third to start timing it. As we only had 2 people, this wasn’t really an option, but it is something that would be worth trying with a third person to have got better results. I did learn from the first time though, and improved my experiment for a second and third time
The results are as accurate as they could be, but if I had only used my 2nd and 3rd results, I think that it would’ve worked better because I learnt a lot from my 1st try that affected the experiment because I corrected it.
Improvements that could’ve been made would be accuracy in gathering the results using better technology, for example, the use of a gas syringe, for a more accurate data collection, and a thermostatic bath, to control the temperature.
My investigation leads me to the conclusion that if I double the concentration of the acid, I double the amount of gas release, therefore there are double as many particles, this increases the reaction time, as double the original amount of particles are colliding. This tells me that me results are accurate and reliable. I believe that the average results of the investigation are correct.
I could have furthered my investigation, such as by trying out the other experiment, calculating and varying the temperature of the acid. My predictions for this would be that the colder the solution is, the slower the reaction will be. I think this because the particles need energy to cause a reaction; this is called its activation energy. Colder particles have less of this, so they are less able to move, as the coldness takes away their energy. So if the cold particles did come together, they need to collide to cause a reaction. As they have less energy, they might not bang together hard enough to cause a reaction, so they just bounce off. But at higher temperatures, the particles move faster, so they collide more often and cause a reaction to happen quicker. Eventually, all of the different temperatures produce the same reaction; it’s just a matter of time! The Colder the acid, the longer it takes, the hotter the acid, the less time it takes. Catalysts lower the activation energy, making it easier for particles to react, so with a catalyst, a lot more particles have the energy to react. The results graph would also show a negative correlation, as the colder the solution is, the slower the reaction is. To do the temperature experiment, I would go about it the same way as I did with the concentration experiment, but heat up the 50ml of 1molar acid at 6 different temperatures. To make it a fair test, in addition to the fair test rules for the concentration test, for the temperature test I am going to keep the acid at 50ml of 1molar strength, and keep the base (marble) crushed and only 1g used.