I will be conducting an investigation into the affect of calcium carbonate reacting with Hydrochloric acid.

I believe that the min chip will have the fastest reaction rate and the mega chips will have the slowest rate, due to their surface area and the collision theory.

Apparatus

* 1 gas syringe - To collect the Carbon Dioxide

* Top-pan balance - to weigh out chips

* Conical flask - in which acid & chip will be placed when experiment takes place

* Beaker full of HCL.

* Many Calcium Carbonate Marble Chips in 3 sizes - MINI, MAXI & MEGA

* Clamp and boss - to hold gas syringe

* 1 bung - to stop gas escaping from conical flask

* Measuring cylinder - to measure out HCL

* Piece of rubber tubing - to connect conical flask to gas syringe

* Blocks - to raise conical flask.

* Small piece of paper.

Safety

Safety as is all experiments is of the highest importance. Safety glasses must be worn at all times and laboratory coats are strongly advised to protect you and clothing. Hydrochloric acid is corrosive care must be taken. It is a good idea to check the apparatus for any broken pieces, that way, injury and mistakes in my experiment through a leak, can be avoided.

Method

Firstly the gas syringe will be attached to the clamp and stand so that the syringe is at a horizontal angle.

Next the conical flask will be placed next to the gas syringe and joined up by a piece of rubber tubing. The conical flask should be raised on blocks so that there is no strain on the rubber tubing and so it is safe.

Next the paper should be placed on to the scales and set the analogue reading to zero so that it only weighs the marble chips. 4 lots of marble chips from each of the 3 groups must be measured out so that they are all equal to 2 grams. 2 grams has been chosen as the most sensible value because due to a preliminary experiment it was found that the value allows the measuring most successfully. Any more than 2 grams was found to be to fast to record the results reliably and any less than 2 grams was found to be two slow and would mean that the experiment would take a lot longer than really needed.

Measure out 50 cm3 of HCL.

Take 2 grams of the calcium carbonate chips from 1 group of mini, maxi or mega, and place them in the conical flask attached to the gas syringe. Poor the HCL into the conical flask. All the marble chips must be covered. As soon as the liquid is poured into the conical flask add the rubber to bung to stop the gas from escaping.

The stopwatch must be started 3 seconds after the flask is bunged. This is because the reaction is not instantaneous and previous experiment proved that this time would mean the result would be more accurate. It was decided from a preliminary experiment that it was ideal to have two stopwatches running and two people running them. This allow the volume of gas to be measure more frequently and accurately.

Measure the volume of Carbon dioxide every five seconds and record the results with units of cm3.

Continue taking the readings every 5 seconds until the gas syringe has reached the end. Then continue to carry out the experiment for the different surface areas (i.e. mini, maxi and mega).

Repeat the experiment so you have 4 sets of results for each of the three groups.

Validity

To ensure that my experiment is fair there are many aspects for me to consider. I must conduct a fair test that I can say that my results are reasonably accurate and reliable.

I am changing the surface area of the calcium carbonate chips in my experiment so all other variables must be kept the same, if they are not then they may interfere with my experiment. Certain factors will be difficult to keep the same such as the temperature but as long as the experiment is carried out quickly and during one session I do not think it will effect my results to the point of them being anomalous.

Secondly, it is important that the same apparatus is used throughout the experiment. For example, the same gas syringe should be used as one may more resistance and friction than the other does. By using the same one all the results will be affect so there would no be unreliability between them. This is a similar case for the top-pan balance in that the same once will be used each time due to the possibility of any technical error or inaccuracies. As before all the results would be affected so this is not so important.

To ensure that my experiment in as accurate as possible I have decided to repeat the experiment 4 time for each of the 3 sizes of chip. As stated above all other possible variables must be kept the same, meaning care must be taken over the measuring of the acid each time. It is crucial that 50cm3 of HCL is measured correctly each time.

Analysing

I used the results obtained to plot the graph on the previous page of Volume (cm3) against Time (secs). The Graph shows that larger the surface area the quicker the rate of reaction. This is largely due to the Collision Theory, and fits to my original prediction; the larger the surface area then the more particles there are exposed to collide. Therefore the more collisions there are between particles in a given time, the faster the reaction.

This explains why the mini chips had a faster rate then the maxi and the mega.

The graph show 3 lines of best fit, which I believe, are reasonably reliable. The steeper the line the faster the rate of reaction. Once again this proves my prediction was correct as the mini chips has the steepest line and the mega the least steep. The maxi chip results are quite close to the mega chip results.

I conclude from my results that the surface area does affect the rate of reaction as my graph clearly shows. The graph is linear which suggests that the rate is possible proportional. I would have originally expected it to charge due perhaps the affect of temperature and the kinetic theory but it did not appear so. This supports the fact that the reaction was not instantaneous. It took a few seconds to for the reaction to speed up and by leaving those three seconds allowed us to get more accurate results. This is called an exponential rate.

Evalutation

I believe that my experiment went quite well. There were no anomalous results and I feel nothing went wrong. I believe my method was one of the most accurate ways to complete this investigation as reflected in my results, which are very consistent. However there are ways in which I would like to increase the accuracy of my method. For example, by having two timekeepers presented the problem of human error. There is a possibility that the stopwatches were started at different times. To overcome this only one person would start the two stopwatches at the same time until the second took over. You have to allow for a margin of human error during the experiment, some people react slower than others and you have to rely on the person taking the readings with the stopwatch.

However, in the experiment I feel the results gathered were very reliable and could only have been made better by a more extensive experiment by perhaps repeating each experiment more than 4 times to get a more accurate average. Overall I am confident that my experiment was a success and the conclusions and the results are correct.

If I repeated this experiment I would take more readings, check all the equipment before to ensure things like the gas syringe aren't stiff which could cause anomalies use one person to start the stopwatch before introducing the second person.

There are many possible extensions to this experiment. I could try to use other carbonates and react them with hydrochloric acid. I could try different acids also and see what happens. All these could help me broaden my knowledge on reaction rates.