Balanced equation: Fe + CuSO4 5H2O FeSO4 + Cu
( 1 molar copper sulphate solution)
Relative 56 + 64+32 +(16 x 4) + 10 + (5 x 16) 56 +32 +(16 x 4) Molecular 56 + (96 +64) + (10 + 80) 88 + 64
Mass: 56 + 160 + 90 152
56 + 250 152
56g of Fe…..reacts with…..1Litre CuSO4
5.6g of Fe..…reacts with…..100ml of CuSO4
0.56g of Fe…reacts with…10ml of CuSO4
Therefore, if I were to place 0.56 grams of iron in 10ml of blue copper sulphate solution, it would be enough iron to react with all the copper.
In this investigation the variables I am going to keep the same to make it a fair test will be:
· The volume of copper sulphate
· The concentration of the copper sulphate
I will keep the volume of copper sulphate the same in this investigation, as it will change the amount of copper molecules, therefore it will affect how much iron it takes to react with all the copper in the solution. If for each mass of iron I put into the solution had a different volume of copper sulphate it would make the investigation unfair; as if each boiling tube had a different volume of copper sulphate we would not see the effect of the increasing mass of iron filings on the rise in temperature.
I will keep the concentration of copper sulphate the same as if I increase the concentration there will be more particles of copper sulphate which will make collision of the particles more likely, therefore it will change the time in which the iron reacts to give a faster rise in temperature.
Preliminary results
To decide my measurements for this investigation I carried out a preliminary investigation at the lowest mass of iron filings I could accurately measure, 0.1grams and at 2.0grams to give me a range of results to show the difference in the rise of temperature. I carried out my preliminary investigation in 10ml of copper sulphate one molar solution. I have decided to record the temperature every minute for four minutes, as I believe this is enough time to see the full rise in temperature for the mass of iron.
The input variable I will be changing in this investigation is the mass of iron filings. I will measure this using an electronic scales correct to two decimal places. I decided from my preliminary results that my smallest measurement would be 0.2 grams as I found that 0.1grams didn’t give me a big change in temperature. I decided for my highest measurement to be 3.2grams, I got 3.2 grams as from 0.2 as I will double it five times to give me five readings, 0.2g, 0.4g, 0.8g, 1.6g and 3.2g. I think this will give me results that will show the effect of different masses of iron filings on the rise in temperature and if the rise in temperature is directly proportional to the increase in the mass of iron; if I double the iron I will double the rise in temperature. At 3.2, I think there will not be much of a difference in the rise of temperature from 1.6 as I am sure that there will not be enough copper in the 10ml of solution for the iron to react with. I am going to repeat this investigation three times and take an average to make sure I get accurate and reliable results.
The outcome variable in this investigation that I will be measuring is the change in temperature, I found from my preliminary results that recording the temperature every minute for four minutes gave me the full rise in temperature for that mass of iron as at 2 grams after four minutes the temperature started to drop. I will measure the change in temperature using an ordinary mercury thermometer.
The apparatus I will need in this investigation are:
· 5 boiling tubes
· Boiling tube rack
· Stop watch
· One molar copper sulphate solution
· Iron filings
· Spatula
· Thermometer
· 10ml measuring cylinder
· Electric digital measuring scales, correct to two decimal places
· Safety goggles
Safety
· I will be careful not to get iron filings in the eyes as they will cause damage
· I will try not to get copper sulphate on the skin as people can be allergic to it and it’s an irritant.
Plan
To carry out this investigation I will carry out the below plan.
· Collect all the apparatus listed overleaf and place them on a clean surface.
· Place all 5 boiling tubes in the rack, measure out 10ml of copper sulphate solution and carefully pour it into each boiling tube.
· Measure out the five different masses of iron filings carefully, using a spatula not to pick up iron filings with your hands.
· Measure the starting temperature of the copper sulphate solution, it doesn’t matter if it is different each time as you will take away the maximum temperature from the starting temperature.
· Wind up the stop clock and get one person to start it as the other pours in the iron filings. Stir the iron filings with the thermometer carefully.
· Every minute for four minutes check the temperature and record it. In between the readings make note of the observation that can be seen, smelt, felt etc.
· After the four minutes stop the timer and place the boiling tube back in the rack. Repeat this for the next four masses of iron filings.
· When the experiment is finished pour the contents of the boiling tubes in a container so it can be disposed of and wash the other apparatus.
· Repeat this experiment twice again.
Analysis
From my graph, overleaf it can be seen that as the mass of iron filings increases; the rise in temperature increases. The reason for this being that a chemical reaction takes place between the iron and the copper sulphate. This is a displacement reaction between the copper and iron. A metal will displace a less reactive metal in a metal salt solution like the one in this experiment this can be seen in the equation below.
Iron + Copper sulphate Iron sulphate + Copper
Fe + CuSO4 FeSO4 + Cu
A chemical reaction is always accompanied by a change in energy. In going from reactants <http://www.gcsescience.com/xm7.htm> to products <http://www.gcsescience.com/xm7.htm>, either
· Heat is given out - called Exothermic
· Heat is taken in - called Endothermic
This particular experiment was exothermic as it gave out heat giving us a measurable rise in temperature. In this investigation the breaking of the copper sulphate bonds required energy; but more energy was released when the new bonds were formed to make the products. More energy was released so it was an exothermic reaction. Consequently as the mass of iron filings increased the number of iron molecules in the solution increased colliding with the same amount of copper molecules, so more new bonds of iron sulphate are formed reacting with more copper molecules increasing the temperature. By looking at the graph it can be seen that the increase in mass of iron filings was proportional to the increase in temperature showing my prediction to be correct, as it is a straight line. Thus showing, that my results agree with my prediction; as the mass of iron filings increases the temperature increases. My results also show that there was a point where the iron had reacted with all the copper. This was at 3.2grams of iron, which only gave a temperature change of 26.6oc, which is much lower than expected according to my graph, which shows the rise in temperature is directly proportional to the rise in the mass of iron filings. The reason this reading was so low was because the iron had reacted with all the copper leaving some iron filings at the bottom of the boiling tube, as there was no more copper for the iron to react with. When observing the reactions I noticed that the copper sulphate had turned completely colourless when I added 3.2 grams of iron, showing that all the copper had been reacted with.
Evaluation
I think the method I used was fairly appropriate as I was able to gain fairly accurate results showing the increase in temperature with the increase in the mass of iron filings. However the disadvantage of the method I used was that heat was lost through the top of the boiling tube and through the sides of the test tube by convection. This affecting the accuracy of my results and could explain why some of my points are a little bit off my line of best fit. I think I used a wide enough range of values as my highest mass of iron reacted with all the copper leaving some iron at the bottom of the boiling tube, so if I had carried out another reading a lot more iron filings would be left at the bottom of the boiling tube. For each reading I doubled the mass of iron filings, as I predicted, the increase in the mass of iron filings was directly proportional to the increase in temperature, therefore I doubled the mass in the hope of doubling the temperature for each reading. I think four minutes was a long enough time to observe the change in temperature as for some of reading on the fourth minute the temperature started to decrease showing that the solution had reached its maximum temperature. I repeated the investigation three times, which I think was enough as I had reading very similar each time showing that I had carried out the investigation in the same way all three times. One problem was that it is sometimes difficult to read the temperature of the thermometer as it would be in between a temperature for example in between 35 and 36oc so it was difficult to determine the temperature this could have affected my results in some way to a certain extent.
My readings were constant and all fairly similar, by just one or two degrees out. This can be seen from looking at my tables for example when I added 0.4 grams of iron filings my change in temperature readings for each repeat were, 5o, 6o and 6oc showing that in each repeat the readings were moderately constant. I had one odd result on my graph apart from at 3.2 grams, which was due to the fact all the iron had reacted with the copper leaving some iron un-reacted. At 0.8 grams my reading is above the line of best fit, the reason for this could have been that I measured to much iron filings, I could easily have done this, as when I was measuring out the iron filings on the scale, if I went over the amount or iron I needed I would take the paper with the iron off the scale and tip a bit of iron off. When I put the paper back on the scale, the scale could have taken into account the weight of the paper. This could have resulted in the odd reading as the scale was accurate to two decimal places so it would have picked up the extra weight of the paper. My results were similar to the results of the other pupils in my G.C.S.E Chemistry class showing my results were accurate.
Changes
If I were to do this investigation again I would make a few changes:
· Firstly, I would try to stop the loss of heat through the top of the boiling tube and convection through the sides by putting a cork in the top and insulation around the boiling tube to stop convection. This would stop heat loss, so I would be able to get a more accurate reading of the change in temperature.
· Or instead of insulating the boiling tube I could do the investigation using polystyrene cups opposed to boiling tubes, I would use the polystyrene cups with lids, in which I could place the thermometer through, this way there would be no or very little heat loss again to give me a more accurate reading for the change in temperature.
· Lastly I would consider increasing the volume of copper sulphate so that I would know that when I add 3.2grams of iron filings there would be enough copper molecules to react with all iron, so I would be able to show that the increase in iron is directly proportional to the increase in temperature. However the disadvantage of this would be as there is twice as much solution than before so it would take twice as long to see the maximum increase in temperature.
Further investigations
For a further investigation I would do this experiment again either using an element that is higher than iron in the reactivity series or lower than copper to show that the displacement would not take place. I would carry out the investigation in the same way as I did this investigation taking in to account the changes that I stated above.
My prediction would be if I used an element like aluminium, which is higher in the reactivity series, than iron; as the amount of aluminium is increased the temperature will increase, I would however expect a larger increase in temperature than with iron, as the element is more reactive.
I could also do an investigation like this one but just using 20ml of copper sulphate instead of 10ml. The investigation would follow the same principle plan as this investigation. By using a higher volume of copper sulphate I will know that there will be enough copper molecules to react with all the iron giving maximum temperature increase. However, as the volume will be higher it will take longer for all of the molecules to react with each other, I predict, as I would be doubling the volume of copper sulphate from this investigation it would take double the time to see the maximum temperature change. The graph would show that the increase in iron is proportional to the rise in temperature for all readings as there would be enough copper to react with the amount of iron added for all the readings.
