On the third test I will use a 45 Degree mixture of Sodium Thiosulphate, water & Hydrochloric Acid.
On the fourth test I will use a 55 Degree mixture of Sodium Thiosulphate, water & Hydrochloric Acid.
On the fifth test I will use a 65 Degree mixture of Sodium Thiosulphate, water & Hydrochloric Acid.
Fair Test: to make it a fair test, I am going to keep the timing person the same and the measurements of Sodium Thiosulphate and Hydrochloric Acid and water the same but change the temperature.
Prediction: I predict that the conical flask with highest temperature will react quickest and the conical flask with the lowest temperature will react slowest. The reason I think this is because of collision theory.
Collision Theory: When the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy. Particles with more energy are more likely to overcome the activation energy barrier to reaction and thus react successfully. If solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur.
Results Table:
Safety Points:
- Make sure all glassware is away from edge of table.
- Put all coats, bags & stools away.
- Make sure water bath doesn’t get too hot.
- Always wash hands when finish.
- Take care of all the glassware.
Conclusion:
From these results we can clearly see a pattern emerging. As I predicted, when the temperature of the Sodium Thiosulphate, water & hydrochloric acid are increased the rate of the reaction increases. The graph shows this pattern taking place as well. From these results we now know that this reaction was a chemical reaction, because it cant be changed back to the separate liquids so we know its not a physical reaction, and the details given from the collision theory explain why the reaction speeds up, with an increase in temperature.
Evaluation
For 50ml of sodium thiosulphate, 10ml of hydrochloric acid, and 40ml of water at 25 degrees it took 60.96 seconds for the cross to disappear. In my 2nd and 3rd attempts at 65 degreees I got 77.56 and 79.7 seconds. This means that the first attempt was probably wrong as it is well below the other 2’s times.
This could have been caused by any number of things such as:
Measuring- the actual measuring of the chemicals is difficult because of the meniscus of the liquid and the accurateness of the measuring cylinders. Also, the human eye causes errors such as this.
The eye could also have made mistakes in judging whether or not the cross had actually completely disappeared
If someone was watching the reaction and someone else was working the timer, errors could occur in their co-ordination.
To further investigate this experiment, I could use a wider range of temperature. I used 25, 35, 45, 55 and 65 degrees celcius in my experimant and so I could use the mid points of these temperatures for more accuracy. I could also go up to 95 degrees to obtain more results but this probally would not affect my experiment as the results are quite hard to record at 65 degrees as the mixture reacts so quickly.
