In order to make the experiment safe goggles and lab coats must be worn at all times as a protection in case of a spillage.
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 (2moles) used in all experiments in order to make it a fair test. The amount of gas produced will be measured (by using scales) as a dependent variable. The temperature will be kept constant as the room temperature.
Analysing the results
From the obtained results I was able to work out the rate of reaction in all 3 test (12 experiments), they are as followed:
Test 1:
- Marble Chip powder took 2 minutes to produce 0.45g of gas in total; therefore the rate of reaction was 0.45 ¸ 2 = 0.23g per minute (to 2 decimal places)
- Small sized Marble Chips took 9 minutes 20 seconds to produce 0.48g of gas in total; therefore the rate of reaction was 0.48 ¸ 9.3 = 0.05g per minute (to 2 decimal places)
- Medium sized Marble Chips took 10 minutes to produce 0.46g of gas in total; therefore the rate of reaction was 0.46 ¸ 10 = 0.05g per minute (to 2 decimal place)
- Large Marble Chips took 9 minutes 40 seconds to produce 0.45g of gas in total; therefore the rate of reaction was 0.45 ¸ 9.7 = 0.05g per minute (to 2 decimal places)
Test 2:
- Marble Chip powder took 1 minute 40 seconds to produce 0.47g of gas in total; therefore the rate of reaction was 0.47 ¸ 1.7 = 0.27g per minute (to 2 decimal places)
- Small sized Marble Chips took 8 minutes 40 seconds to produce 0.46g of gas in total; therefore the rate of reaction was 0.46 ¸ 8.7 = 0.05g per minute (to 2 decimal places)
- Medium sized Marble Chips took 9 minutes 40 seconds to produce 0.46g of gas in total; therefore the rate of reaction was 0.46 ¸ 9.7 = 0.05g per minute (to 2 decimal place)
- Large sized Marble Chips took 10 minutes to produce 0.45g of gas in total; therefore the rate of reaction was 0.45 ¸ 10 = 0.05g per minute (to 2 decimal places)
Test 3:
- Marble Chip powder took 3 minute 40 seconds to produce 0.42g of gas in total; therefore the rate of reaction was 0.42 ¸ 3 = 0.14g per minute (to 2 decimal places)
- Small sized Marble Chips took 9 minutes 40 seconds to produce 0.48g of gas in total; therefore the rate of reaction was 0.48 ¸ 9.7 = 0.05g per minute (to 2 decimal places)
- Medium sized Marble Chips took 10 minutes to produce 0.43g of gas in total; therefore the rate of reaction was 0.43 ¸ 10 = 0.04g per minute (to 2 decimal place)
- Large sized Marble Chips took 10 minutes to produce 0.43g of gas in total; therefore the rate of reaction was 0.43 ¸ 10 = 0.04g per minute (to 2 decimal places)
I have chosen to repeat the experiment 3 times in order to allows me to calculate an average rate of reaction. This increased the accuracy of the obtained results.
From the table of results and the graphs I can deduce that by increasing the surface area the rate at which the gas was produced also increased. The line which represented the amount of gas given off on the graph was steeper in the test using powder therefore the gas was produced at a faster rate. Roughly the same amount of gas was produced in all tests. Therefore my hypothesis was correct.
Evaluation
As I repeated the experiment 3 times and worked out the average rate of reaction in each test, I think my results are quite reliable. However, I could make further improvement by increasing the number of tests and taking the results with a smaller gap such as 10 seconds instead of 20. I could also increase the amount of Calcium Carbonate to more than 2g and keep the amount of acid as 50ml; which would slow down the reaction and will allow me to take more accurate results, as it would decrease the number of anomalous results.
Conclusion
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, Carbon Dioxide was given off at a quicker rate. Therefore the rate of the reaction slowed down as the size of the particles was increased from powder to 9-12mm pieces.
