List of equipment:
- 10ml test tube
- 1 set of scientific scales
- 1 thermometer
- 6 test tubes
- Test tube rack
- Glass rod
- Spatula
- Safety mat
- Bunsen burner
Safety:
- Safety glasses
- Long hair tied back
- Use safety matt under Bunsen burner
Method:
Analysis of results:
I can see by looking at the results I recorded and the graph I have drawn that salt E was the best at providing water when heated. I can see this by looking at my graph showing that salt E had the most amount of water available and its mass reduction was the highest showing that it released a high amount of water. By looking at the tables containing the results from experiment two; I can see that salt D needed the lowest temperature to give off its water. However if I combine the two tables from experiment 1 and 2, I can see that the reason for this was because salt D had only a small amount of water to give off therefore it did not need a large amount of energy. Salt E however did need a larger amount of energy than salt D but due to its large amount of water being given off. If we were to take this into account then we would see on the whole that salt E needed the least amount of heat energy to release the most amount of water.
Any compound, which contains water in the form of H20 molecules, is capable of dissolving; the best-known hydrates are those that are crystalline solids, which loose their basic structure on the removal of bound water. However, the reason that salt E was the best at providing water was because salt E is made of sodium which is an alkali earth metal this makes salt E soluble and combined with carbonate it becomes sodium carbonate (Na2Co3). Even though carbonates are insoluble, anything (compound) containing an alkali earth metal will be soluble. So if sodium carbonate (Na2Co3) were to be added to water it will readily dissolve. This explains why sodium carbonate, salt E was the best at providing water; because if you were to have a certain amount of water then more of salt E would dissolve in the water than salts B and D meaning that more of the salt could fit into a certain amount of water than the other two metals.
Evaluation:
As I did the experiment twice I believe my results are reasonably reliable as, by calculating averages I was able to eliminate any one-off errors that may have occurred during the experiment, and averaging my results also made them more accurate therefore more reliable. I believe my observations and recordings are accurate and reliable enough to base a firm conclusion on. And I believe if someone were to repeat these experiments I do believe that their results would be relatively close to mine, as they are reasonably similar when I repeated each experiment myself. I do not believe however that there is sufficient evidence to draw more than one graph, as I am able to analyse the evidence just by looking at the tables and I believe that the tables contain a sufficient amount of evidence to base my conclusion on. No graphs are needed to show hidden patterns in the data so not much can be said in the analysis about graphs drawn to represent data.
I believe that all my equipment was accurate and the readings that I recorded were also. I have reason to believe this, as I made sure I calibrated the scales before each time I used them and the measuring cylinder was very accurate as it measured to the nearest ml. I may however have gained some false readings from the thermometer although I did try and hold it as close to 90° as I could but I had nothing to measure my accuracy with.
On the whole I believe my experiment went well as I found the instructions for the method easy to follow. I did however find it hard when we reydrated the salts and had to add the water because some of the salts were extremely hard to break up. Therefore in order to break them up we needed to use a glass rod but also take the temperature of the reaction at the same time.
If I were to make any changes the method then I would change the sentence which says “check that no water can be seen anywhere in the tube if there is warm to evaporate it” as I do not believe it is clear enough, it could say, “ stop heating when all the steam has gone and reweigh”. I would also change the part which says “allow to cool and reweigh”. I believe this is very dangerous as someone may touch the test tube to make sure it is cool and if the it is still hot then it may burn him or her. I believe it needs to have a time limit as to when the test tube would be cool or instructions that say to take the temperature with a thermometer to make sure it is cool. I do not think that any further work can be done as I believe that the experiment produced a sufficient amount of evidence to base a firm conclusion on.
If I were to do the experiment again I would make sure I had equipment that checked the accuracy of what I was doing. I would also do the experiment three times instead of twice as I could then calculate averages that could be extremely reliable.
