Apparatus
For this experiment I will need thermometer, small measuring cylinder, large measuring cylinder, beaker, retort stand, pen, piece of paper, hydrochloric acid, sodium thiosulphate, 2 test tubes, goggles, sticky label, bunsen burner, stop watch, conical flask, gauze, heat proof mat and finally a tripod. I am going to be performing to experiments that are both related. All the apparatus may not be used in both experiments.
Methord1
Concentration- This is how I will carry out my experiment:
- Gather the equipment
- Set it up as shown in the diagram
- Get 50cm³ of sodium thiosulphate and 10cm³ of hydrochloric acid using the large measuring cylinder for the sodium thiosulphate and the small measuring cylinder for the hydrochloric acid
- Pour the chemicals into the conical flask
- I would pour the contents of the small measuring cylinder in second because this will take less time meaning the chemicals will have less time to react before you start the stop watch
- Start the stop watch after you have finished pouring both of your chemicals into the conical flask
- Stop the stop watch when the cross on the piece of paper is no longer visible
- Clean out the flask thoroughly to make sure there are no chemicals remaining
- Be sure not to reverse the way you are using the measuring cylinders otherwise the chemicals will start reacting before your put them in the conical flask
- Repeat this experiment 3 times
- When you have repeated this 3 times dilute the sodium thiosulphate with 10cm³ of water.
- Continue to dilute by 10cm³ each time and repeating each experiment 3 times
- Obviously don’t just use 50cm³ of water because no reaction will take place
Temperature- this is how I will carry out my experiment:
- Set up equipment as shown in diagram
- Put goggles on
- Get 10cm³ of hydrochloric in the small measuring cylinder and 10cm³ of sodium thiosulphate and 40m³ of water in the large measuring cylinder
- Put a sticky label around the test tube that will have the hydrochloric acid in always put the hydrochloric in this test tube and the thiosulphate and water solution in the other
- Put these in the beaker of water and heat them until your get to the correct temperature
- Measure the temperature with a thermometer in the water surrounding the 2 test tubes
- When you reach the correct temperature pour the contents into the conical flask
- Stop the stop watch when the cross on the piece of paper is no longer visible
- Clean out the flask thoroughly to make sure there are no chemicals remaining
- Be sure not to reverse the way you are using the measuring cylinders otherwise the chemicals will start reacting before your put them in the conical flask
- Repeat this experiment 3 times
- When you have repeated this experiment 3 times do it again at temperatures from 30°C – 70°C
- There is no point in exceeding 70°C because the rate of reaction begins to become to fast to measure
- Below 30°C the temperature is too low and the experiment takes too long
Pilot experiment for concentration reaction results
Pilot experiment for temperature reaction results
I was satisfied with the results I obtained from the concentration experiment therefore leading me to believe that the method was sound. I was not satisfied with the results I had gotten from the temperature experiment I had over looked a key factor, there was 5 times more liquid in one of the test tubes so this was taking longer to heat up. If I was to wait for this to get to the right temperature then the test tube with the hydrochloric acid in would be too hot. I solved the problem by getting an extra thermometer and extra beaker. Instead of measuring the temperature of the water I would measure the temperature of the test tubes contents. The second beaker I would use to cool the test tube with the hydrochloric acid in while the test tube with the sodium thiosulphate continued to heat.
Methord2-
Temperature- I have made some modifications to my method this is how it will be carried out now:
This is how I will carry out my experiment:
- Set up equipment as shown in diagram
- Put goggles on
- Get 10cm³ of hydrochloric in the small measuring cylinder and 10cm³ of sodium thiosulphate and 40m³ of water in the large measuring cylinder
- Put a sticky label around the test tube that will have the hydrochloric acid in always put the hydrochloric in this test tube and the thiosulphate and water solution in the other
- Measure the temperature with a 2 thermometers one in each test tube.
- Allow the hydrochloric acid to exceed the desired temperature by 10- 15°C
- Then take the test tube out and place it into the beaker of cold water while that is cooling down the sodium thiosulphate will be heating up
- When you have the two chemicals at the correct temperature place them in the chonical flask
- Start the stopwatch when both chemicals are in the chonical flask
- Stop the stop watch when the cross on the piece of paper is no longer visible
- Clean out the flask thoroughly to make sure there are no chemicals remaining
- Be sure not to reverse the way you are using the measuring cylinders otherwise the chemicals will start reacting before your put them in the chonical flask
- Repeat this experiment 3 times
- When you have repeated this experiment 3 times do it again at temperatures from 30°C – 70°C
- There is no point in exceeding 70°C because the rate of reaction begins to become to fast to measure
- Below 30°C the temperature is too low and the experiment takes too long
Fair Testing
I will maintain the fairness of this test by washing out the necessary equipment EG: the equipment that is required to handle more than one of the chemicals. I will start the stopwatch after completely pouring the second chemical into the flask so as each experiment is measure the same. Use the measuring cylinders to regulate the amounts of each chemical going into the experiment as accurately as possible. Each experiment will be done at least 3 times to ensure that I have done each experiment correctly and give me more reliable results. I will keeps the amount of hydrochloric acid constant throughout my experiment and during the temperature experiment I shall keep the amounts of each chemical the same the only variable will be the temperature the experiment takes place at.
I will do my best to keep the experiment safe by wearing goggles at all times when handling chemicals or using the Bunsen burner. I will not sit down while doing and experiment so that if a spill should occur I can quickly get out of the way without been harmed.
Results
This experiment was done with 10cm³ of sodium thiosulphate and 40cm³ of water because this was the slowest reaction when doing the experiment for concentration so it would be easier to measure the time and attain more accurate results.
These experiments were done with 10cm³ of hydrochloric acid and variations in the amount of sodium thiosulphate and water the sodium thiosulphate
Sodium Thiosulphate + water = 50cm³ of solution
This is the formula I used to work out my averages
A + B + C 68 + 68 + 61
------------- ---------------- = 66
D 3
Conclusion
My results lead me to believe that my prediction was correct. The higher the temperature rose the quicker the reaction took place. The higher the concentration the quicker the reaction was. I can’t say my prediction is 100% correct because I have not produced enough results.
Scientific Explanation
My results closely convey what I predicted because of the science behind the experiment when the molecules are heated they have more kinetic energy the more heat they get the more energy they can gain and the more energy they have the more they can move quicker and also alt more. If the molecules are moving more they are going to collide with other molecules more often causing more reactions to take place in a shorter amount of time. If there is more active liquid EG: in this case sodium thiosulphate then it will not take as long for the hydrochloric acid molecules to find a sodium thiosulphate molecule that they can react with where as if there is less of the substance it will take long for the sodium hydrochloric acid to find a molecule it is capable of reacting with.
Some of the results I have however do not fit this pattern there are a couple of explanations for this.
- The room temperature could have varied from day to day when I was doing my experiments.
- Human error I may not have washed thoroughly enough or measured the liquids accurately
- I may have on occasions started the stop watch earlier of later than I should have done
- I may have just read the time on the stop watch incorrectly
Evaluation
I had a couple of anomalous results each are circled on my results table and were missed on when recording averages because they would have consequently also effected my averages and made them also anomalous. The only reasons for these results were such things as human error and miss-judgment for example miss reading the thermometer one person may have had better eye sight than the other he/she was working with meaning on person could still see the cross and the other not. Not washing out the apparatus thoroughly enough. Final reason was I used the temperature of the room on the day I did the concentration reactions and assumed it was the same temperature when I did the temperature reactions. I would like to carry on the experiment and carry on further work with it one of the things I would like to do is another experiment at 30ºC I am not sure if any which one of these results is anomalous. I would like to carry out more experiments exceeding 70ºC to see weather the rate of reaction continues to rise of weather and some point the line begins to level out. I could carry out more experiments that would enter the graphs on the curve to gain a better and more accurate graph. I could also investigate how pressure can change the rate of reaction does it slow or speed it up, maybe introduce a catalyst to speed up the reaction or even investigate how surface area affects the rate of reaction.
By Robert Sanderson
