Access to standard apparatus- 1 small measuring cylinder, 1 large measuring cylinder, 1 beaker and 1 pair of goggles.
Plan
Get the apparatus- beaker; paper marked with an X, and two solutions- Hydrochloric acid and Sodium Thiosulphate. Place the beaker on top of the X and add 10cm3 of Hydrochloric acid and 30cm3 of Sodium Thiosulphate.
The solution will then be timed how long it takes to become cloudy and that the X cannot be seen. I will the repeat this procedure with different concentrations of Sodium Thiosulphate. Things that will change during the experiment are the concentration of the sodium solution.
Things that will stay the same are the amount of Hydrochloric acid, 10cm3, and the amount of Sodium Thiosulphate, 30cm3.
To make the experiment safe I will wear safety goggles and afterwards I will wash my hands.
To make the test fair I will use the same volume of hydrochloric acid and sodium thiosulphate, I will also clean the beaker after each reaction and I will start the stopwatch at the same time, each time.
Fair Testing
To keep my experiment fair I will use the same amount of Hydrochloric acid and Sodium Thiosulphate although the concentration will change for Sodium Thiosulphate. I will also start the stopwatch at the same time throughout; this will be as the second solution is being poured.
Keeping my test fair will mean that my results will be more accurate.
Prediction
I think that as the concentration of the Sodium Thiosulphate gets stronger, the reaction time will become faster. This is because that the higher the concentration the more particles, so there is more chance of the particles colliding and producing a reaction.
Results
Conclusion
In my experiment I found that as the concentration got higher the reaction became quicker. This is because that as the Sodium Thiosulphate’s concentration got higher, there was more particles. If there are more particles then there is more chance of the two solutions colliding and therefore producing a faster reaction.
In my prediction this is what I had wrote and so my prediction was correct.
My graph shows the gradual decline in a slope, which starts high with the concentration being at its weakest and getting smaller as the Sodium Thiosulphate gets quicker in time to react and stronger in concentration. The slowest time was 76 seconds when the Sodium Thiosulphate was at its weakest, and its fastest time to react was 15 seconds when the Sodium was at its highest concentration.
Evaluation
I think that my experiment went quite well; we performed a safe and fair test completing the task on hand.
If I was to change the experiment to make it better I would use a more accurate way to measure the time of the reaction and I would also use more concentrations of Sodium Thiosulphate.
