Plan on Reaction of Calcium Carbonate and Hydrochloric Acid.

For the experiment I will use 1g of ground up marble, 1g of marble chips and 1g of marble cubes. The volume for the marble cube is 1cm2 the medium sized chips are 6-9mm2 and there is no way of knowing the are of the ground up marble. They will be placed inside 100 ml of Hydrochloric Acid. Keeping the mass of the marble the same and the concentration of Hydrochloric acid will make it a fair test and not affect the rate of reaction. For the experiment I will place the measured pieces of marble one for each experiment into the acid. At that point of contact I will start the stopwatch to time and keep track of the experiment. I will time the experiment within 2 minutes and take down how far the gas syringe has moved every 10 seconds from the gas given off. With the results taken down I will transfer the data on to a table.

I had to change the masses of the ground up marble from 1g to 0.70 grams. The reason for this is because within the 10 seconds the gas syringe had gone from 0-100 cm3 too quickly. Before the experiment I worked on Multimedia Science School, I changed the surface areas and how it changed the rate of reaction. If you change the surface area there is a higher proportion of particles on the outside of the substance. This makes more room for particles to collide and more of a chance to collide. This factor increases the rate of reaction.

Here is a table for my results I collect:

Time/seconds

Volume of Gas/ cm3

Marble Cube

Marble Chips

Ground Up Marble

2

3

2

3

2

3

0

20

30

40

50

60

Hypothesis

Using my knowledge of the collision theory I predict that the smaller surface area the rate of reaction will increase. If you increase the surface area there are more chances that the reagents will collide with each causing a reaction. Relating this to my experiment the largest surface area is ground up Calcium Carbonate. This means I predict that this will have the fastest rate of reaction and the marble cube will have the slowest rate of reaction because it has the smallest rate of reaction to its volume.

Analysis

From my experiment I found out that changing the surface area of the marble pieces does affect the rate of reaction because of the collision theory. It states that if you increase the surface area the rate of reaction will increase also because there is a larger chance that the reagents will collide and react. This proves that my prediction was correct. Each experiment reacted faster. It changes because each time I increased the surface area the rate of reaction increased. It took less time for the reaction to finish. You can see this by looking at the graph in the first ten seconds the marble chips produced twice as much gas than marble cubes did with the smaller surface area. You can look again ground up marble produced ten times more gas than the marble chips did in the first ten second. You can see this if you look at my graph, I took the averages of each experiment that I repeated three times and then plotted the results. You can see that the largest surface marble pieces on the graph aren't as steep compared to the other results which means that the reaction was slower. The next more reactive reaction was the marble chips which has a larger surface area than the marble cube, then the quickest was the ground up pieces of marble with the smallest surface area. This proves my theory that by increasing the surface area it increases the rate of reaction. The values from the graph prove my theory. The ground up marble pieces produced 50cm3 of gas in ten seconds, the marble cubes (the largest surface are out of all three experiments) took 70 seconds to produce 50 cm3 of gas. I predicted that the rate of reaction would increase with increasing surface area and I was correct because the results graph shows that the steeper the slope the more amount of gas is being produced in a shorter time. The collision theory states 'the more collisions between particles in a given time, the faster the reaction'. This relates to my experiment that I got more gas and reactions in a shorter time, which implies a faster rate of reaction.

Evaluation

I think the procedure of my experiment was very good but it could have been more accurate with better equipment. The gas syringe produced a lot of friction which would have restricted movement of the syringe being pushed backwards from the collected gas. Another thing that prevented me getting accurate results was when I pushed the bung into the test tube it also pushes air into it. To prevent this I could disconnect the tube which would allow the trapped air to escape. This would push air into my test tube and prevent it escaping. Due to school equipment my results had some anomalies in it, in the marble cube experiment at 100 seconds the result was just above the line of best fit. With more accurate equipment this would be corrected. One problem I had was with the ground up pieces of marble it was too reactive for the experiment, when I tried to time the experiment it was all over within ten seconds. It was a problem because I couldn't take down the gradual increase of gas being produced the experiment was over to quick. I could improve the experiment if I lubricated the gas syringe to reduce even more friction, which would affect the amount of gas being collected and if had a more accurate gas syringe, which gave more detailed measurements. My experiment is reliable if I repeat it again I would get the same results because each experiment I repeated three times and got very similar results each time. If I repeated it I would not use random sized marble chips as they would each have a different surface area preventing my results to be as accurate as they can be.

My results prove that surface area does make a difference, but it doesn't prove how much surface area does make a difference because I only used three very different amounts. It does not make accurate enough results to state exactly how much will make a difference to the rate of each test.

Matthew Broomfield 121 Stowe School