Before conducting an actual investigation, I will carry out a preliminary test,
which will allow me to grasp the general idea of this study. For this practice test, I will use the temperatures 20-70°C, going up in intervals of 10°C.
Hydrochloric acid + sodium thiosulphate sodium chloride + sulphur dioxide + sulphur + water.
2HCl + Na2S2O3 2NaCl + SO2 + S + H2O
Method
- Measure 15 ml of Hydrochloric Acid, and 10 ml of Sodium Thiosulphate into appropriate measuring cylinders. Use pipettes for accuracy.
- Pour each solution into a test tube and place a thermometer in to each test tube.
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Set up water bath and place test tubes into it. Check that temperature of both the solutions is at 20°C. Remove from beaker and pour the solutions one after the other into conical flask, which should be placed on top of an A5 piece of paper with a cross. Start stopwatch as soon as the second solution is poured.
- Keep watch over solution. As soon as mixture clouds and the cross is not visible, stop the timer immediately. Record time taken for the reaction to happen in a table.
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Wash all equipment used. At a temperature of 30°, repeat test again. Wash equipment after every test.
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Then again at temperatures of 40°C, 50°C, 60°C and finally 70°C, do the test again. Record all results in table.
Health and Safety
- All loose clothing should be tied back, e.g. scarf. Hair should not be kept loose either.
- Work surface should be clear, with the exception of all experiment apparatus.
- The kettle should be positioned safely, with no wires hanging down, and care should be taken when pouring out hot water.
- Do not run whatsoever.
- Do not spill solutions.
- Do not pour solution back into the bottle, as this will contaminate it.
- Make sure you know which solution is which, do not mix solutions up, and do not insert pipettes used for one solution into another.
- Wash all equipment after every experiment.
- Keep all stools tucked under benches, so tripping doesn’t occur, and in case of emergency, getting out is easier.
Apparatus
- Hydrochloric Acid
- Sodium thiosulphate
- 2 test tubes
- 10 ml measuring cylinder
- 15 ml measuring cylinder
- 2 pipettes
- Stopwatch
- Conical flask
- Beaker
- Kettle
- A5 piece of paper with cross drawn on
- 2 thermometer
Variables
Time taken for each test (control)
Amount of solution (measure)
Temperature (change)
To make a fair test I intend to keep some things the same and others different. Things I will keep the same are:
- Amount of solution in each test
- Interval between the different degrees of temperature
- Person keeping watch over cross so perspective of when the cross disappears stays the same
- Person with stopwatch so time taken in starting and stopping it is the same
- Temperature for both solutions in each different test
Things I will change are:
Prediction: I predict that the higher the temperature, the faster the reaction will be.
Preliminary Results
For my real investigation I will be making a few changes to the preliminary method. In the above I experiment I used 15ml of Hydrochloric Acid and 10 ml of Sodium Thiosulphate. I will change these amounts to 10 ml HCl and 25 ml of Na2S2O3. Furthermore, I will conduct the experiment at an additional temperature of 80°C instead of just stopping at 70°C.
Method
1. Measure 10 ml of Hydrochloric Acid and 25 ml of Sodium Thiosulphate. Use pipettes for accuracy.
2. Pour each solution into a test tube and place a thermometer in to each test tube.
3. Set up water bath and place test tubes into it. Check that temperature of both the solutions is at 20°C, then remove from beaker and pour the solutions one after the other into conical flask, which should be placed on top of an A5 piece of paper with a cross. Start stopwatch as soon as the second solution is poured.
4. Keep watch over solution. As soon as mixture clouds and the cross is not visible, stop the timer immediately. Record time taken for the reaction to happen in a table.
5. Wash all equipment used. Repeat the experiment at same temperature (20°C) each time recording the results. Wash all equipment after every test.
6. At a temperature of 30°, repeat test again 3 times.
7. Then again at temperatures of 40°C, 50°C, 60°C, 70°C and finally 80°C do the test again. Repeat each temperature thrice. Record all results in table.
Apparatus
- Hydrochloric Acid
- Sodium Thiosulphate
- 2 test tubes
- 10 ml measuring cylinder
- 15 ml measuring cylinder
- 2 pipettes
- Stopwatch
- Conical flask
- Beaker
- Kettle
- A5 piece of paper with cross drawn on
- 2 thermometers
Variables
Time taken for each test (control)
Amount of solution (measure)
Temperature (change)
To make a fair test I intend to keep some things the same and others different. Things I will keep the same are:
- Amount of solution in each test
- Interval between the different degrees of temperature
- Person keeping watch over cross so perspective of when the cross disappears stays the same
- Person with stopwatch so time taken in starting and stopping it is the same
- Temperature for both solutions in each different test
Things I will change are:
Prediction
I predict that the higher the temperature, the faster the reaction will be. My prediction is based on the factors which affect rate of reaction (as mentioned before) and the one in particular relation to my prediction is the factor showing that heat causes particles to collide more, thus speeds up reaction. Because the particles then have more energy to react, they crash together quicker. Temperature in this case also acts as a catalyst. It gives energy to the particles, so they do not need too much of their own activation energy to start the reaction of. The collision theory is involved here as it is the name given to the reactions happening after particles collide together.
Health and Safety
1. All loose clothing should be tied back, e.g. scarf. Hair should not be kept loose either.
2. Work surface should be clear, with the exception of all experiment apparatus.
3. The kettle should be positioned safely, with no wires hanging down, and care should be taken when pouring out hot water.
4. Do not run whatsoever.
5. Do not spill solutions.
6. Do not pour solution back into the bottle, as this will contaminate it.
7. Make sure you know which solution is which, do not mix solutions up, and do not insert pipettes used for one solution into another.
8. Wash all equipment after every experiment.
9. Keep all stools tucked under benches, so tripping doesn’t occur, and in case of emergency, getting out is easier.
The average time was calculated by adding all three rates of reaction times and dividing them by three. Rate was calculated by dividing 1 by the average time.
Conclusion
After completing both preliminary and real investigations, and thoroughly studying the results, it is obvious that temperature is a factor which increases the energy level of particles. From looking at the graphs and tables I saw that at first, when the temperature was low, the reaction took place at a slow pace. However as the temperature was increased interval by interval, the reaction time also went up.
The average time graph shows clearly as the temperature went up, the time it took went down. For example, at the temperature of 20°C, the time taken for the reaction stood at 87.6 seconds. However by the end of the experiment, as the temperature increased by 60°C, reaching 80°C the time taken decreased greatly, standing at an evidently low time of 6.7 seconds. The slope descends evenly, showing that as the temperature increases, the reaction takes place quicker.
The rate graph shows that as the temperature went up, so did the amount of product produced per second. Again using the figures from before, at 20° C, the time taken for product to be formed was 0.011 seconds. However, this increased and as the temperature rose to 80 degrees Celsius, the time, rising with it went to 0.149.
The collision theory shows us how particles can collide together, and this factor, (increased temperature) is one which speeds the rate of reaction up. From the evidence obtained, it is clear that my prediction was correct. However, as mentioned before anomalous results were obtained showing that either the prediction was not 100% accurate, or that the results were due to mistakes made during the course of the experiment. The results of both real and preliminary investigation gave near accurate results, the numbers always similar to each other.
Evaluation
The method used for the investigation was a suitable one. It included all aspects of the investigation and clearly gave step by step instructions. Therefore the results produced were all relating to each other sensibly.
Plausible reasons for the anomalous results attained could be either that the attention of the person who had been watching the solutions could have been diverted, or that there may have been a less accuracy in measuring the solutions, or perhaps the stopwatch wasn’t stopped immediately. Either reason suggests to me that it was a mistake of students, and not any specifically scientific reason. However, it could also have been that the acid solutions used were contaminated at any point during the investigation.
To improve the results, a graduated pipette could have been used for more accuracy in measuring the solutions. This would have allowed me to specify an amount, and have the exact number given out, rather than letting inaccuracy ruin the results. In addition to that, a water bath could have been used for more precise temperatures and would also have proved to be more easy and efficient to use rather than having to dunk test tubes in and out of a beaker. If these suggestions would be used in another experiment, I would have used the same method as before, only in the water bath suggestion, I would have set the temperatures from before instead of having to warm up water again and again.
An extension to the investigation could have been that in addition to using the temperatures used, cold temperatures could also have been used to give a more variety of results. This could have been put into practice using an ice- bath, but with the same method as before, using cold temperatures as well as warm. Also, the rate of reaction on other acids could have been done with the two acids already used. I may have added Sulphuric Acid in with the two solutions already used, thus providing a different reaction.
Time taken at different temperatures for HCl and Na2S2O3 to cloud completely
Rate (1/Average time)
