How does temperature affect the rate of a reaction?
Lucy Gillett
How does temperature affect the rate of a reaction?
What am I trying to find out?
In this investigation I am trying to find out if and how temperature affects the rate of reaction between magnesium ribbon and hydrochloric acid.
What am I going to do?
* I will firstly collect all of the equipment.
* I will then put 20cm of acid into the boiling tube.
* I will then place the boiling tube into the water bath and allow the water to reach the desired temperature.
* I will then place 2cm of magnesium ribbon into the 20cm of 1.0 moldm-3 of acid, as I do this I will start the stop watch.
* Once the magnesium has reacted I will then stop the stopwatch and record the time.
* I will then repeat this experiment so that I can get an average.
* Once I have done that I will repeat the experiment for all of the 6 temperatures. Which are: 10°C, 20°C, 30°C, 40°C, 50°C and 60°C.
What do I think will happen?
I think that the higher temperature will increase the rate of reaction. So the higher the temperature, the faster the rate of reaction. I think this because of the following:
The rate of reaction is the speed or velocity at which a chemical reaction precedes, expressed in terms of the amount of product formed or the amount of unit´s time taken for a certain reaction to occur (usually in seconds). Thus for the reaction of two compounds (in this case X and Y) that form a product (Z) the equation would be:
X+Y=Z
The Rate of Reaction varies greatly. Some chemical reactions, such as explosions, happen very quickly while others like rusting occur very slowly. The rate of reaction can be affected by a number of factors: temperature, concentration and pressure, adding a catalyst, surface area/particle size and light. The one that I am going to be investigating and explaining about is Temperature.
Changes in temperature change the kinetic energy of the particles and hence the numbers of successful collisions with enough energy to break existing bonds and make product parties. The minimum energy needed for a successful collision is called the activation energy.
For a reaction to take place reagent molecules must collide with each other. When they do so, they must possess enough energy to cause or initiate a reaction. The level of energy needed to start a reaction is called its energy barrier. The actual energy needed to start a reaction is the activation energy e.g. a splint is needed to start a Bunsen burner in the process of combustion.
So in order to break the energy barrier, there has to be enough activation energy so the reaction will take place. Temperature helps to do this as increasing the temperature of the system increases the range of kinetic energies, increases the average kinetic energy and increases the population of particles with more than the activation energy.
Reaction mixtures contain particles that have different amounts of energy. Some particles are of very high energy whilst others are of relatively low or medium energy.
The two theories that affect temperature and the rate of reaction are the kinetic theory and the collision theory. The kinetic theory clearly states that the positioning and movement of particles in a substance increases if the temperature increases. Therefore, increasing the temperature increases the energy between the particles and makes them move around a lot more and collide more often with each particle colliding with enough energy to get ...
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Reaction mixtures contain particles that have different amounts of energy. Some particles are of very high energy whilst others are of relatively low or medium energy.
The two theories that affect temperature and the rate of reaction are the kinetic theory and the collision theory. The kinetic theory clearly states that the positioning and movement of particles in a substance increases if the temperature increases. Therefore, increasing the temperature increases the energy between the particles and makes them move around a lot more and collide more often with each particle colliding with enough energy to get it past the energy barrier. If this is done successfully, then the collisions should have no problem passing the requirement stated in the collision theory that are: To react particles must collide with enough energy to break existing bonds and with the correct orientation to bring reactive sites close together.
Bringing the reactive sites closer together means that the likelihood of a reaction occurring is increased so in a final research conclusion, increasing the temperature increases the rate of reaction speed.
What Equipment will I need to complete the experiment?
Other Equipment includes:
* Stopwatch
* Pipette
* Measuring Cylinder
How will I make it a fair test?
There a few different procedures to follow, that would enable my experiment to be a fair one. To make my experiment a fair one, I had to look at a lot of things. Firstly, I looked at the factors that may have affected how well the investigation would work and these were things like using different equipment or doing the actual experiment in different conditions i.e. a colder/hotter environment. To combat this, I made sure that upon repeating the experiment, I used the exact same equipment and done it in the exact same environment to make absolutely sure that the experiment was fair at each temperature.
I think that these were both very important factors because they could affect the results severely and leave me with an anomalous when I should only have correlating results. To ensure fair and accurate results, all of the factors that can affect my results need to be controlled. Some other methods to make it fair include:
* I will keep the concentration of the acid the same
* I will keep the volume of acid the same
* I will keep the length of ribbon the same
* I will make sure that the temperature required is correct, and to the exact desire.
* I will also record true results.
* I will do each temperature twice, which will allow me to get an average.
What safety precautions am I taking?
Throughout this experiment, I will make sure that safety is one of my top priorities. I will wear goggles at all times to protect my eyes; I will also wear a lab coat to prevent getting any chemicals on my clothing or me. As i was using highly flammable, corrosive and harmful chemicals, I felt this necessary. I also used the basic laboratory safety measures such as hair up, chairs under tables and a clear and clean surface to work on.
Which variables am I changing?
There are many variables which can be changed in some way to effect the reaction, I have chosen to change the temperature. I have chosen 6 different temperatures to complete the experiment with, and hope that these temperatures will show a pattern into the increase of temperature and rate of reaction. My temperatures are: 10°C, 20°C, 30°C, 40°C, 50°C and 60°C. I found when choosing my temperatures there were two limits these being 0°C and 100°C, as at 0°C the solution would freeze and at 100°C the solution would evaporate.
Which variable am I going to measure?
I will be measuring the rate of reaction. This being how long it that's for magnesium to react with hydrochloric acid. I will be measuring in seconds.
Bibliography
To complete my planning I used a books and sources as reference to my knowledge. These are:
* Classwork Notes
* Nelson Module Textbook
* Revision Guide
My Results
Temperature
Experiment one
Experiment two
AVERAGE
0°C
24
26
25
20°C
7
21
9
30°C
4
4
4
40°C
1
9
0
50°C
5
9
7
60°C
5
5
5
Analysis
As you can see from the graph and table, my results to show a trend, that the higher the temperature the faster the reaction, this trend also supports my prediction.
The line created on the average graph is a very good result. You can see that there is a steady decrease in time of reaction. You can also see that as the lower temperature increased the decrease of reaction time was higher than those of the higher temperatures increasing.
All rate of reaction experiment have visible results and this experiment is no exception. When I added the magnesium ribbon to the hydrochloric acid I immediately observed a reaction between these particles.
When observing the experiment, the changes I saw take place were the tone of the magnesium /hydrochloric acid solution. At the initial temperatures, which were quite low, the solution slowly reacted causing the magnesium to react and disappear but only after a fairly long time. At the higher temperatures, the reaction was the same as the lower temperature, but happened a lot faster. As the reaction took place a gas was given off and during the reaction there was a mild vigorousness taking place in the test tube.
From my results, I notice that there is a considerable difference in the time for the cross to disappear from the lower temperatures to the higher temperatures. All of the times are pretty much the same for the two different recordings indicating that the experiment was a pretty successful one. There is only one anomalousness this being on the first experiment where 50°C and 60°C reacted in the same time, even though there was an increase in temperature. The average temperature descends, as the temperature gets higher. There is a decrease of 20 seconds from the starting temperature to the finishing one. The table clearly shows that the time for the ribbon to disappear decreases as the temperature increases.
The reaction between Magnesium and Hydrochloric Acid
Magnesium(s) + Hydrochloric Acid (l) Magnesium Chloride (l) + Hydrogen (g)
Mg(s) + 2HCL(l) MgCl2(l) + H2(g)
From my results, I have come to the conclusion that if the temperature of a solution is raised, so is the time for the reaction to occur. The ribbon disappeared more rapidly as the temperature rose and I think this was due to the increase of energy between the particles and an increase in energy between collisions that successfully passed the energy barrier. At the lower temperatures, the time for the ribbon to disappear was less because the particles did not have as much energy as they did at the higher temperatures. At these temperatures the particles are colliding with much more energy, thus causing more collisions.
Linking Prediction to Conclusion
My original prediction was that if you increase the temperature of a reaction, you decrease the time it takes to occur. And, from looking back on my results, I can see that this hypothesis was correct as the time for the reaction to take place decreased as the temperature rose. My conclusion matches my prediction very well overall, and my results clearly show this where at 10°C, the time for the reaction to take place was 25 seconds and at 60°C the time for the reaction to happen was 5 seconds, a difference of 20 seconds. The particles were moving around with more energy; enough to break the energy barrier and for a reaction to occur as the temperature rose.
Evaluation
I think that this experiment has gone very well for me. My results were of a particularly accurate standard as I did each temperature the reaction was taking place two times and calculated an average from these times. There was only one strange result (anomalies) within my results table, as I stated before, and I think that this was probably because the desired temperature wasn't correct. Except for that odd result the others were very good and positive, I took extreme caution and care that I put into making sure that the experiment was set up correctly with careful measuring of chemicals, temperature and substances.
I think that I could have repeated my results more however for the reason that I feel although the experiment was repeated twice, the most accurate results in experiment can only come from constant repeatability which I did not display in my experiment. That said, the time allocated did not allow me to do so and I believe as an improvement of what I could do if I did the experiment again, I would have to say that, with more time, I would repeat the results further for even more accurate and reliable results.
I believe that I could have improved the method by making it more specific. I stated clearly all the various methods I took in setting the experiment up but I could have been more specific to how all the apparatus was used and perhaps why I used the apparatus I did as well.
I believe that I did get a suitable range of results for this experiment. I recorded results from temperatures that ranged from 10°C to 60° C and I think that this is a very good range to see how temperature affects the rate of reaction. However, I feel that this also reduces the chance of knowing if anything changes if the temperature reaches a certain point. Perhaps doing the temperature even higher would enhance my results, and make a clearer and more scientific response and results.
Some other areas in the experiment that I feel I could have improved on were factors like controlling the stopwatch and measuring the amount of sodium hydrochloric acid and length of ribbon. There is lots of room for human error here. However the inaccuracies due to them were negligible because I paid close attention to these during the experiment.
Overall, this investigation has been a very successful one. I feel my results and analysis have been as accurate and reliable as they could have been under the time allocated. However I feel with extra time, I could have repeated the experiment and made it even more accurate and adapted it to try other variables i.e. concentration or adding a catalyst. These are the ways that I could expand on the original question.
Lucy Gillett Science Coursework 1
Rate of Reaction
