Surface area - If one of the reactants is a solid then breaking it up in to smaller pieces will increase its surface area. This means the particles around it in the solution will have more area to work on so there’ll be more useful collisions.
Temperature – When the temperature is increased the particles all move quicker. This means that they will have more collisions.
Catalyst – A catalyst works by giving the reacting particles a surface to stick to where they can bump in to each other. This increases the number of collisions too.
To make the test fair I must keep the temperature of the sulphuric acid the same. To do this I can use a water bath.
If we do not keep all the volumes of sulphuric acid the same then it would be unfair because at a higher temperature there are more collisions. To keep it the same we can use a water bath.
If we do not brush the magnesium with sandpaper the test could be unfair because the impurities could speed up or slow down the reaction.
Measurements
I will change the concentration of the sulphuric acid during my experiment. I will be using vols.
0.5 1.0 1.5 2.0 2.5.
I will take two readings to allow for errors as I am not likely to get perfect results and am more likely to get it right on a second reading. I will average these results to draw a graph.
I will try to take very precise measurements.
Prediction
I predict that as we increase the concentration the speed of the reaction will increase.
I think this is because increasing the concentration means there are more particles of reactant around which makes collisions more likely. More collisions mean more reactions.
Scientific Knowledge
The collision theory describes the way temperature, concentration and surface area of the reactant affects the rate of reaction, by affecting collisions between particles. Particles react when they collide with sufficient energy. At a higher temperature collisions are more frequent and also have more energy because the particles are moving faster.
Reactions only happen if the particles collide with enough energy. At a higher temperature there will be enough energy to make the reaction happen. This initial energy is known as activation energy and its needed to break the initial bonds.
At a higher concentration collisions are again more frequent, as there are more reactant particles in the liquid. This means that there are more likely to be collisions and so the reaction is speeded up.
In our case increasing the concentration of the sulphuric acid is increasing the chances of it bumping in to and reacting with the magnesium therefore creating a more vigorous reaction.
Forming this equation:
Sulphuric acid + magnesium + magnesium chloride + hydrogen
H SO (1) + MG(5) = MGSO (1) + H
2H + SO - + MG+ = MG +SO - + H+
Preliminary work
Preliminary method
- Cut the magnesium ribbon 1cm long
-
Put 10cm of sulphuric acid of different concentrations each time in different beakers
- Measure temperature of sulphuric acid
- Add the magnesium ribbon and time the reaction.
- Measure temperature of sulphuric acid.
- Repeat for different concentrations.
- Put your results of the reaction time in a table
- Draw a graph of your results.
Diagram
Preliminary results
Conclusion
My results are fairly good but I do have an anomalous result, which I have shaded. This could be due to not sanding it properly or measuring inaccurately.
As you can see the time of the reaction goes down fairly rapidly and so I will change 10cm of sulphuric acid to 20cm .
Obtaining
Method
See preliminary method but change 10cm to 20cm of sulphuric acid.
Results
Average results
My results support my prediction.
Analysis
I have found that as you increase the concentration of sulphuric acid it speeds up the reaction with the magnesium ribbon.
(See graph)
My graph shows that as concentration increases the time of the reaction decreases.
It shows a negative correlation.
This is because
Evaluation
My experiment was quite successful and my results show a fair trend.
I had two anomalous results, which could have been because of inaccurate readings or the experiment not being fair. It could also have been due to inaccurate measurements. (I have circled these on the graph).
My method was quite suitable although I do admit that I didn’t follow it very precisely.
To improve my results next time I could try more repeat readings or following my instructions more carefully.
My results are fairly reliable however the anomalous results show that it could have been better.
My results show that they support my conclusion because as the concentration goes up the time goes down.
The limitations of evidence making a firm conclusion are that
I could improve my method by writing in to use sand paper to use on the magnesium. This could get any impurities off the magnesium, which could interfere with my results.
Another experiment I could do which could increase the reliability of my results is with hydrochloric acid and magnesium.
Hydrochloric acid and magnesium
In this experiment I am going to see how changing the concentration of hydrochloric acid will affect the rate it reacts with magnesium. I will be measuring the amount of gas produced in this experiment.
Method
Put 25cm of hydrochloric acid in a conical flask.
