The steps I need to control throughout the experiment to keep it a fair test are the volume of water [so it adds up to 50cm with] the Sodium Thiosulphate and I will also need to keep the hydrochloric acid at 10cm.
Apparatus
The apparatus needed for this experiment are the following:
- 100cm measuring cylinder
- 10cm measuring cylinder
- 100cm beaker
- 2 conical flask
- A stop clock
- Hydrochloric Acid [1m]
- Sodium Thiosulphate
- Distilled water
This diagram shows the experiment when its all set up.
Method
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First, I need to measure 50cm of Sodium Thiosulphate, and add 0cm of distilled water and place both in a 100cm beaker.
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Second, add 10cm of Hydrochloric Acid to the mixture of distilled water and Sodium Thiosulphate.
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Third, place the beaker on a clear piece of white paper with a cross marked in the middle of it, and start the stop clock.
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Fourth, watch carefully to see the mixture turn cloudy and for the cross to disappear.
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Fifth, when the cross has disappeared completely, stop the clock and record the results in your table.
These are the steps that needs to be repeated:
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First, to change the concentration of the Sodium Thiosulphate by adding enough distilled water so they both add up to 50cm.
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Second, timing the rate of the reaction and recording it in the table.
Observation
I will need to record the amount of distilled water used, the amount of Sodium Thiosulphate, the time it took for the cross to disappear and the amount of Hydrochloric Acid used each time. To get accurate results, I need to be close to the experiment in order to read the time on the stop clock.
The table below is the table that I used to record my results:
Analysis
This graph shows that the more distilled water you add to the Sodium Thiosulphate it becomes more diluted and so takes longer for the cross to disappear.
- The results show that when the Sodium Thiosulphate is diluted with distilled water the concentration becomes low causing less collisions between the particles, it shows also that the sulphur takes longer to become precipitated out of the solution.
- In solutions of higher concentration particles are closer together. They have a greater chance of colliding, because there are more collisions , the reaction rate is greater.
- My results matched my prediction because I predicted that the more distilled water you added to the Sodium Thiosulphate the longer the sulphur takes to turn into a solid.
Evaluation
The experiment turned out well because we got accurate results that we could rely on, as being true.
The results were accurate because we used the same equipments to do all the experiment. This makes it accurate because we used the same stop clock which meant that we didn’t get any result that didn’t fit the pattern of the experiment.
The method we used gave results that were reliable because they all fitted in the pattern. We repeated the experiment twice and the results continued to fit the same pattern.
We had a range of results to draw a conclusion. We used five solutions and repeated our experiment 2 times. This got us accurate results because we also found the average of the set of results that we collected from our experiment.
Another way that we could have done our experiment was to use a different solution and compare the two set of results to see which one gives a more accurate result.
