One of the first and most obvious variables is the metal carbonate I will use. This is one of the factors that I will continually change. I will have a range of five different metal carbonates because different metals have different rates of reactivity. The metal carbonates that I am going to use are;
- Sodium Carbonate
- Calcium Carbonate
- Magnesium Carbonate
- Zinc Carbonate
- Copper Carbonate
Although I will change each type of metal carbonate, the amount of molecules in each metal carbonate needs to be the same. The mass of each compound cannot be kept the same because, for example, there are more carbonate molecules in Calcium Carbonate than there are in Copper Carbonate. So instead of the metal carbonates being measured in grams they will be measured in moles.
Another factor I will keep the same is the length of time I heat the metal carbonates for because, obviously, the longer I leave the carbonates to decompose the more time I will be allowing for the reaction to take place and as a result more carbon dioxide will be produced. In order to obtain reliable results each metal carbonate must be heated for the same amount of time.
The temperature of the type of flame I use to heat my carbonate and the distance between the test tube containing the carbonate and the flame. Both factors must be kept constant. A tall yellow flame on a Bunsen burner is the coolest setting and gives of the least heat whereas a roaring blue flame is the hottest setting and gives of the most heat. The type of flame needs to be kept the same so that the same amount of heat is given off and therefore the same amount of energy is transferred into the decomposition of each metal carbonate. The same concept of keeping having the same amount of heat and energy being transferred into each compound applies to the distance between the test tube and the flame. This is because, logically, the closer the test tube is to the flame the hotter the carbonate will become and the more energy will be transferred. Just as the further away the test tube is to the flame the cooler the carbonate will be and therefore less energy will be transferred into the reaction and so less carbon dioxide will be produced.
Prediction:
I predict that the longer I heat the metal carbonates the more carbon dioxide that is produced because the longer the compound is left to heat the more energy that is transferred into breaking the bonds between the carbonate and the metal atoms. Also along these lines, I predict that the higher the temperature I heat the metal carbonates the more rapidly carbon dioxide will be produced. This is because the hotter the temperature the more energy is being transferred in the time given and so more bonds can be broken more quickly.
I also predict that the metal with the most reactive metal in it will have the metal carbonate that decomposes the slowest and therefore produces the least carbon dioxide which means that the metal should produce the least reactive compound. I think this because the more reactive the metal is the stronger the bond between the carbon and the oxygen is and so in order to break up (or decompose) these metal carbonate molecules a lot more energy is needed and because I am heating all metal carbonates at the same temperature and for the same amount of time the most reactive metal will have the least reactive compound and so will produce the least amount of carbon dioxide. In order of reactivity (most reactive to least) the metal carbonates I am using are;
-
Sodium Carbonate (NaCO3) → Sodium is the most reactive metal out of the five that I am investigating and so Sodium Carbonate should be the least reactive compound therefore producing the less amount of carbon dioxide
-
Calcium Carbonate (CaCO3) → Calcium is the second most reactive metal out of the five and so should have the second least reactive metal therefore producing the second less amount of carbon dioxide
-
Magnesium Carbonate (MgCO3) → Magnesium is the third most reactive metal out of the five and so should have the third most reactive compound therefore producing the medium about of carbon dioxide
-
Zinc Carbonate (ZnCO3) → Zinc is the second least reactive metal out of the five and so should have the second most reactive compound therefore produce the second highest amount of carbon dioxide
-
Copper Carbonate (CuCO3) → Copper is the least reactive metal out of the five and so should have the most reactive compound and therefore producing the most carbon dioxide
So just as the more reactive metals form stronger bonds with the carbonates the less reactive metal form weaker bond with the carbonates. This means that the weaker bonds take less energy to break; this rate of thermal decomposition is shown by the rate at which carbon dioxide is produced or the amount produce in the time given. So as I have said, the least reactive metal should produce the most carbon dioxide. In short this means that, logically, the more reactive the metal, the less reactive the compound and the less carbon dioxide is produced.
Preliminary Test:
In my preliminary test I need to find out;
- The ideal amount of carbonate to use
- The amount of heat required
- The size of gas syringe to collect the carbon dioxide given off
- The time needed to produce an accurate amount of carbon dioxide
So that I can plan my actually experiment so I can get the most accurate results possible.
In my preliminary test I decided to test Copper Carbonate (CuCO3) because this is the copper carbonate that will produce the most amount of carbon dioxide and so via this I can find an idea amount of carbonate which doesn’t produce vast amounts of carbon dioxide but still produces enough to give reliable data.
I used a 100ml gas syringe to collect the carbon dioxide produced and this was an amble size. I found that in 4 minutes I could produce roughly 50-60ml of carbon dioxide from 0.2g of Copper Carbonate. The Relative Formula Mass of CuCO3 is 123 and so one mole of copper carbonate has a mass of 123g to find how much of a mole is in 0.2g of copper carbonate I did this equation;
Mass (g) = Moles (mol) x Relative Atomic Mass (Ar) or Formula Mass (Mr)
or
Moles (mol) = Mass (g) / Relative Atomic Mass (Ar) or Formula Mass (Mr)
0.2 / 123 = 0.00162602
And so through this I found that the ideal measurement for each metal carbonate that I will use in my actually experiment is 0.00163 mol. I heated the copper carbonate on a blue flame and at a distance of 10cm from the nose of the Bunsen burner.
Method:
Apparatus:
- Bunsen burner
- Heat proof mat
- Gauze
- 2 clamps stands
- Gas syringe
- 8 test tubes
- Bung and piping
Diagram:
As in the diagram, I will set up my apparatus, clamping the Bunsen burner containing the first metal carbon over the Bunsen burner at a 10cm distance from the nose. This test tube will be joined via bung and piping to the gas syringe that has a scale of 100ml (with 1ml intervals) that will measure the carbon dioxide produced.
Previously I will have measure each metal carbonate so that each one has the same amount of 0.00163 moles which I will calculate by take the Relative Formula Mass and multiplying it by 0.00163 (the amount of moles) and this will give me the mass that I need of each compound.
Then I will light the Bunsen burner on a blue flame and begin the timer. I will measure the amount of carbon dioxide that has been produced for each metal carbonate every minute for four minutes, recording my results in a table. And each time I change the substance that I am decomposing I will change the test tube so that they are no trances of any other carbonates when each one is burnt – this should reduce the amount of anomalies I get in my data and give me accurate results.
Results: