When particles collide with each other, they do not always react. Sometimes the particles don’t have enough energy for the bonds to stretch and break during collisions so the products cannot form. The particles don’t have the minimum amount of energy. This minimum amount of energy is called activation energy.
‘Chemical reactions occur when particles of the reaction collide. They must collide with a certain minimum energy, called the activation energy.’ (Taken from workbook.)
In the test where the acid was at 14 C not many of the particles had the required amount of activation energy, this means that there are very few successful collisions. Most of the particles just bounced off of each other. In the experiment where the acid was at 60 C a lot of the molecules had the required amount of activation this meant that there was a lot more successful collisions therefore the bonds were broken more efficiently and the reaction took less time.
The conclusion I have made supports my prediction by saying that the hotter the acid the quicker the rate of reaction. We still don’t know however if there is a point below 14 C if no reaction occurs because in the test we did, the lowest temperature we did was 14 C Also we don’t know if there is a point above 60 C if the reaction cannot become quicker because the highest temperature we did was 60 C.
Evaluation
For this experiment my prediction was correct. My results have proven that the hotter the acid the faster the rate of reaction. Our results were good because we only had one anomaly. The anomaly was at 27 C. All in all the experiment was successful and we proved our predictions right. There was however one anomaly and this could have been due to a number of reasons. If I did the experiment again I would only change a couple of things. First thing would be the accuracy of the measuring of the magnesium, we only used scissors and rulers to measure the amount of magnesium and this could have easily caused variations in length therefore altering the time taken to react. To solve this problem we could have used knifes to cut more accurately. Also when we heated the beakers up to the correct temperature e.g. 50 C we did this by placing the beaker in a pan of hot water then used a thermometer to tell the temperature. When the temperature was at the desired amount we then took the beaker out of the water and then put the magnesium in the beaker. This means that all the time the magnesium was reacting the temperature was becoming lower. Conversely when we cooled the acid down to 14 C and took it out, the acid began to heat up again. Using controlled temperature water baths could easily solve this.
I would say that our results are pretty reliable, because we did what was asked to a sufficient degree and did it accurately. I have enough evidence to support a firm conclusion but only between 14 C and 60 C, I have proved that between these two figures magnesium reacts quicker in hotter acid than in cooler. However I have not proved this for example 80 C this might be the temperature where the magnesium cannot react any quicker therefore even if the acid was at 90 C the reaction time would be the same. I also cannot make a firm conclusion below 14C for instance 5 C this might be the point where no reaction occurs at all so even if the acid were at 1 C there would be no difference in the time of reaction.
All reactions go faster at a higher temperature. Temperature has a very noticeable effect the rate of many reactions is doubled by a temperature rise of just 10 C. If I did the experiment again I would initiate my improvements and also do a test showing higher and lower temperatures e.g. To find out if there is a temperature below 14 C where by the reaction doesn’t occur for example -20 C, I would use a freezer to find out if this is true. To see if there is a temperature above 60 C where the reaction doesn’t take place I would use acid at 100 C to test this by using a water bath. I would do both these implementing my experiment changes