Method
- Take one large piece of Calcium Carbonate and record its weight.
- Measure 100cm³ of hydrochloric acid (using measuring cylinder).
- Place the flask on the scales.
- Add the marble chip and hydrochloric acid to the conical flask at the same time.
- Start the stopwatch.
- Record the weight loss (gas given off) every 30 seconds for the 3 minutes of the reaction, then every 1 minute for 2 minute, then every 2 minutes until the reaction stops.
- Repeat the experiment using medium sized marble chips.
- Repeat the whole experiment again using large marble chips. Make sure you take the same amount of chips (in weight (roughly)) and hydrochloric acid at each time in each different experiment.
- If time allows, repeat all the experiments in order to improve the reliability of the results.
In order to make the experiment safe goggles and lab coats must be worn to protect you in case of a spillage; however, lab coats are not a necessity but would be advised.
The independent variable in my investigation will be the surface area of the Marble Chips, however their mass will need to be controlled as well as the amount of hydrochloric acid and its concentration in all of the tests in order to make it a fair test. The temperature will be kept constant as the room temperature.
Analysing the results
I made tables to show my results for each size of calcium carbonate chips.
Table of results of small chips/powder:
From my table above I can see that for the first minute of the reaction, the mass of the small calcium carbonate chips dropped quite dramatically from 110g to 106.33g. However, after that the mass of the marble chips dropped quite slowly as the table shows us that in a matter of 8½ minutes the mass of the marble chips only dropped by 0.26g.
The reaction stopped abruptly after 9 minutes and did not react with the hydrochloric acid after that.
Table of results of medium sized calcium carbonate chips:
From the table shown above, I can see that the mass of the medium sized chips reduced quite quickly and kept an almost equal speed of reaction. The total loss of mass of the marble chips over 21 minutes was 3.71g. The reaction however did not finish because we ran out of time during the experiment.
Table of results of large calcium carbonate chips:
From this table, I can see that the reduction of mass of the large calcium carbonate chips is gradual. The total loss of mass of the marble chips over 1460 seconds or 21 minutes was 3.7g, this was very similar to the medium sized calcium carbonate test that I did. This could have been because in this test I used 110cm³ of hydrochloric acid and in the other tests, I used only 100cm³ of hydrochloric acid.
Therefore, my conclusion would be to say that, increasing the surface area increases the chance of the particles hitting the reactant (colliding) and allows more particles to react with the reactant all at once. The bigger the surface area of Calcium Carbonate, the greater the number of collisions. Therefore the rate of the reaction slowed down as the size of the particles was increased from powder to medium sized to large lumps.
