Variables
Independent variables (what I will change)
The carbonates
Dependant variables (what I will measure and observe)
The time taken for a reaction to take place
Control variables (what I will keep the same)
The amount of carbonate (1g)
The amount of lime water (2ml)
Use Bunsen burner in the same way in each experiment.
Put 1g of the carbonate in a boiling tube.
Fit a delivery tube and then clamp the boiling tube so that the delivery tube dips into a second test-tube containing 2ml of limewater.
Heat the carbonates till lime water turns milky, keeping track of time.
Lift the delivery tube from the limewater before the heating is stopped. This is to avoid suck-back.
Write down all observations. Notice what happens to the limewater and how long it takes to turn milky. Notice whether any melting occurs in the heated test-tube and any colour changes taking place.
Repeat the experiment with the other metal carbonates supplied, and in each case write down your observations.
Anomalies
These are results that are abnormal and random. The anomalies on my results are circled. The reasons for these are a random or human error.
Expected results
The results that I expected to come out with are that the calcium carbonate will have no change to the limewater and a small volume of gas is produced due to thermal expansion. I also expected the zinc carbonate to turn light yellow and the lime water to become cloudy and the copper carbonate turns black and the lime water becomes cloudy but more quickly than the zinc carbonate.
Conclusion
From my evidence I think that the copper carbonate is most easily decomposed as the reactions are easier to see and the results show that the lime water turned milky just after 1 minute.
My results support the hypothesis by showing that copper carbonate decomposes more easily than zinc carbonate and calcium carbonate. Copper is less reactive than calcium, that’s why copper carbonate decomposes more easily than zinc carbonate. The easiness of decomposition enlarges in order of: calcium carbonate, zinc carbonate and copper carbonate. This relates to the reactivity series.
There is a big difference between the 3 carbonates and when repeating the experiments it is obvious. This makes the evidence strong. The collected evidence could be improved by giving a wider range of metal carbonates to test.
The experiment was easy to set up but it was difficult to heat the carbonates the same way each time as the clamp was constantly moving whenever we removed the boiling tube but did not seem to affect the results as they were all accurate. Some of the powder did not reach the bottom of the boiling tube which means that it would not get heated as strongly and would take longer to decompose.
The hypothesis taught me that some metal carbonates decompose more easily than others when heated.