1 x 10cm measuring cylinder to measure the correct amounts of HCl, again 10cm is the amount we need so this will be the easiest and most accurate to measure it with. Safety Goggles, to protect your eyes from the harmful chemicals, if something does get in your eye wash it quickly with clean water then report it too the teacher Lab coat, this is in case any chemicals are spilt, this will protect from the harmful ones. Again report spillages to the teacher in charge.
Preliminary Data: CONCENTRATION OF Na S O TIME TAKEN in SECONDS 40cm 0cm water 30 20cm 20cm water 50 10cm 30cm water 120 6cm 34cm water 220 4cm 36cm water 330 We have decided that the range should be from 10% to 50% because at 10% it approximately 5 minutes and at 50% it takes approximately 1 minute, so this range is good for this experiment in the lab because if the time was any faster it would give unreliable results and if it were and slower we would not have enough time to complete the experiment in the laboratory.
Method: 1. Make sure you are wearing safety goggles and a lab coat to protect yourself from the chemicals, because they can corrode or burn skin. 2.
Collect the apparatus needed and set up as shown in the diagram below. 3. Measure out 20cm of Na S O with 20cm of water for the first reading, it will always add up to 40cm so as to keep a fair test, use the 5 cm measuring cylinder for this. And measure out the amount of HCl , this we are keeping constant so will always be 10cm, this we will use a 10cm measuring tube for. 4. Take a beaker that can hold 100cm. 5. Pour in the Na S O solution and then quickly add the HCl all 10cm at once and start the top watch immediately, give the beaker to swirls, no more because this could create an unfair test.
6. Keep the beaker on plain white paper with a black mark on. 7. When the black mark is completely obscured by the solution stop the watch. 8. Take down the readings carefully in a results table. 9. Do this with each concentration of Na S O and then repeat the experiment 3 times to help obtain reliable results, and to help pick out any anomalies. Diagram:
Results Table: HCl in cm Na S O in cm Water in cm Time in Seconds Average Time in Seconds Ratein Cm/sec X 100 1st Reading 2nd Reading 3rd Reading Rate = Number of Collisions per Second per Cm Analysing The Experiment: In this experiment I have found that when you increase the concentration of Na S O , when mixed with HCl it reacts faster than when the concentration is lower. I repeated each reading 3 times to get the most accurate results I can.
I have drawn up a graph to show the change in volume/concentration of Na S O against the time taken for the liquid to turn opaque and me not being able to see the black dot underneath. The graph has a steady curved line of best fit that shows the time increases more and more as the concentration decreases in equal steps. Conclusion: The graph of rate of reaction against concentration Na S O shows an increasing straight line of best fit, this tells us that the rate of reaction increases steadily with almost no curve in the line of best fit when concentration of Na S O is increased.
The graph is proportional because it has a straight line of best fit. As the input variable increases steadily the output variable increases in proportion with it, the output is the rate of reaction and the input is the volume of Na S O in Cm The reason the rate of reaction increases in proportion to the Na S O, is because when the amount of Na S O goes up there is a higher concentration of Na S O to collide with the HCl, so there is a larger chance of the particles colliding and creating a successful collision.
So if there are more successful collisions the mixture will turn the cloudy yellow colour faster. Evaluation: This experiment was quite a good success because the results helped me to prove my prediction, the graphs showed good straight lines of best fit with no anomalies. There are no anomalous results because all the points on the graph fit the line of best fit and they all follow this same pattern so they are all reliable. The practicality of the experiment is quite easy to perform, but some features do make it difficult to take very accurate readings.
The dot underneath the beaker in which the reaction takes place would sometimes vary in size and in shade of black. Using the same dot for every reaction could help this. The beaker would pick up a residue of Sodium from the reaction, which would make the beaker seem slightly cloudy to start with, so after a few reactions the beaker would begin to build up quite a thick residue, this could be helped by either using a different beaker for each reaction or by cleaning the beaker thoroughly.
Also the light can effect how easy it is to see the dot through the liquid, if there is a bright light in the lab then it will be easier to see the dot through the liquid, so it will take longer the for the dot to be obscured. You could use a light meter to check that the light is always the same when you check for the dot to be obscured. I dont feel the evidence is fully reliable, because there are at least 3 things that can be done next time to improve the experiment, I also feel that there is always a margin of human error, but this is hard to eliminate.
I think also that taking more results would help to make the graphs and conclusions more reliable. Matt Barnes 10-2 Dr. Cruise Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.