‘Faster Collisions are only caused by increasing the temperature’. Reactions only happen if the particles collide with enough energy. At higher temperatures there will be more particles colliding with enough energy to make the reaction occur. This initial energy is known as the Activation Energy, and it is needed to break the initial bonds.
To prove my hypothesis I am going to investigate how the rate of a chemical reaction can be affected by the temperature, by performing an experiment. In the experiment my reactants will consist of Hydrochloric Acid and Marble Chips. I have chosen this as an experiment because the reaction produces a gas known as Carbon Dioxide (CO2). By performing this experiment I can measure the volume of gas involve, with a gas syringe, and take readings at regular intervals.
The Experiment
To perform this experiment I will need some apparatus. This will consist of: -
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Conical Flask (25cm3)
- Delivery Tube
- Burette
- Balance (2 d.p.)
- Gas Syringe
- Bunsen Burner
- Funnel
- Stop Clock
Method
- Weight 10g of 12mm Marble Chips
- Measure 25cm3 of Hydrochloric Acid (HCl) using a burette
- Place acid into a conical flask.
- Add Marble Chips
- Straight away put the delivery tube into the top of the conical flask
- Immediately start the stop clock
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Record how long the reaction take to produce the designated amount of Carbon Dioxide (Every 10cm3)
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Redo experiment heating the acid at stage 3 to the designated temperature (Every 10oC starting at 20oC)
- Redo all experiments performed twice
Overleaf is the table in which I plan to record my result
Whilst I was researching this particular experiment I came across a very similar experiment in GCSE Double Science Chemistry The Revision Guide, edited by Richard Parsons. In this they suggested particular times and amounts of Carbon Dioxide to collect which I have chosen to use.
Must do’s
- Take regular readings from the gas syringe at regular times.
- Put the results in a table and plot a graph
- Repeat the experiment at least 5 times with the temperature of the acid increasing, but always the some amount of Marble Chips.
- The volume of the acid must always be kept the same too. Only the temperature should increase.
- Redo all experiments (stage 9) twice because I want to be accurate and sure of my results.
Whilst doing this experiment I have to remember that the Hydrochloric Acid (HCl) is highly corrosive and therefore I must avoid contact and wear goggles at all times. I’ve taken precautions by wearing goggles, having my hair tied up and rolling up my sleeves.
To keep this experiment a fair one, I had to keep all variables the same apart from the temperature. The other variables were:-
* Surface area of the marble chips
* Concentration of the acid
* Amounts of material used.
I made sure I used the same amount of marble chips and hydrochloric acid each time. As well as making sure the concentration of hydrochloric acid was the same. Finally I made sure to keep the surface area of the marble chips the same, by only using 12mm ones. I also need to make sure that the temperature stayed at a constant for each individual experiment. I did this by putting my conical flask into a water bath. By doing this I avoided allowing the temperature to fall a great deal whilst I conducted the experiment. If the temperature did drop I was only by one or two degrees and therefore it’s neglectable.
I repeated the experiment and took averages of the reading, both to get a more accurate reading. I then recorded my results in a table and plotted graphs.
These are my results that I obtained from my experiment however, once I examined them I found out that the result for 50oC for test 1 was the same as the result for 60oC for test 2 (the ones in bold) and therefore some type of inaccuracy must have occurred. I will repeat the 60oC tests to make my results more accurate.
I have produced two graphs with the results I obtained. One to show how the temperature affects the rate of a chemical reaction, and the other to show the average speed at which that affect happens. The graph shows that as the temperature rises so does the speed of the reaction. This fits my hypothesis and is due to the Collision Theory. This states that the rate of a reaction simply depends on hoe often and how hard the reacting particles collide with each other. The basic idea of the theory is that the particles have to collide and collide hard enough to react. Fast collisions increase the rate of reactions. So the higher temperatures increase the energy of the collisions, because it makes all the particles move faster.
‘Faster collisions are only caused by increasing the temperature’. Reactions only happen if the particles collide with enough energy. At high temperatures there will be more particles colliding with enough energy to make the reaction occur. This initial energy is known as the Activation energy. The Activation energy is the amount of energy required to break the bonds. I.e.
The graph also shows a smooth curve that becomes horizontal as it reaches the higher temperatures. This is because at whatever temperature, the reaction is never instantaneous.
So to conclude. I conclude that as the temperature increases so does the rate of a reaction, however, the reaction is never instantaneous as all my results clearly show. My experiment went well and there were no anomalous results once I had sorted out the minor error I made. I can therefore presume that my results are likely to be accurate as I took averages of my results which are all within 5% of each other and that any conclusions drawn from this experiment are genuine. Although I felt I was quite accurate I have some ideas which may gain even more accurate readings. Firstly, the surfaces of the marble chips were not perfect. It could have been made better by using powdered marble chips because the surface areas would have been a lot closer together. However, if I was to do this the concentration of the hydrochloric acid would have to be weaker or the reaction would take place far to quickly to be recorded. Secondly, human error may have played a part. To resume this I would have to take care to read things accurately and redo all experiments as I did.
There are many possible extensions to this experiment. I could try different acids to react with the marble chips or different carbonates to react with the hydrochloric acid. I could even try to react different carbonates with different acids. All of the extensions could help me to broaden my knowledge of rates of reaction.
