This means that there will be more fruitful collisions per second.
So: The hotter the substance: the more fruitful collisions there are: the faster the reaction takes place.
Preliminary outline:
There are limits as to how much preliminary work can be carried out in this investigation.
I researched the subject carefully by reading books and looking on the internet but I also got an idea of how to carry out the experiment from my chemistry teacher.
Variables:
Method and apparatus:
Apparatus:
- Bunsen Burner
- Mat
- Gauze
- Thermometer
- 2 x Beakers
- 1 conical flask
- 2 Measuring cylinder
- 1 piece of paper with a cross on it
- Hydrochloric acid
- Sodium thiosulphate.
Method:
-
Draw a cross on a piece of paper and place it under a conical flask so you can see it from the top. (See right.) →
- Measure 50 Ml of Sodium thiosulphate and 5 ml of hydrochloric acid.
- Measure the temperature of the sodium thiosulphate and note it down.
- Put the Sodium thiosulphate into a conical flask, add the acid and start the timer.
- Measure how long it takes for the cross to become invisible as the chemicals turn cloudy. When it is no longer visible, stop the timer and note down the time.
- Repeat the exercise but this time heat the Sodium thiosulphate in a beaker on a Bunsen burner to a desired temperature before adding the Acid.
Safety:
- Make sure no chemicals come in contact with the skin or eyes.
- Wear goggles
- Don’t pick up hot Tripods or Bunsen burners.
Important- use the same amount of each chemical each time and use the same cross because if you use a different cross , one might be more prominent than the other.
I intend to get accurate results by:
- Carefully measuring out the chemicals.
- Making sure the chemicals are clearly named.
- Rinse the conical flask out before re-using it.
- Allow for the thermometer to adjust to the temperature of the Sodium thiosulphate so I am sure of the temperature.
- Use the same cross.
- Repeat the experiment to reduce risk of anomalies and to get an average.
I Predict that:
As temperature increases the time taken for the cross to disappear will decrease because the particles will have more energy and cause more fruitful collisions a lot quicker.
More fruitful collisions means the reaction will happen quicker and when the reaction takes place the chemicals turn misty making visibility a lot harder.
Sufficient energy: Reaction occurs
Insufficient energy : Particles rebound.
Obtaining evidence
Results:
*Seems to be quite a difference between the times on both attempts.
Average time taken for cross to disappear
Quality of evidence
I think the results were sufficient. They weren’t entirely accurate but good enough to learn from. It is clear to see there is a definite increase in amount of reactions per second with temperature.
I think also the results were reliable and must be correct to some extent because they all fit into a line of best fit and I do not see one anomalous average.
The closest thing to an anomaly I discovered was a 7 second difference between two readings. This probably came about because it is hard to get the temperature right and to start and stop the timer at the right time.
Apart from the one slight anomaly I didn’t find any more in my results.
Improvements and further work.
If I was to do the investigation again I would find a more suitable way of measuring when the reaction was compete because it was hard to tell if you could still see the cross. It would be a good idea to get water from thermostatic vat so I know the water was exactly 10 Oc warmer each time.
If I had more time I would have used one more different temperature of Sodium thiosulphate to see if there was any more of a decrease because the differences each time did start to slow down.
Overall I think I carried the investigation out well. This method gives a good insight into what happens in general but I would have to use more scientific apparatus not available to me if I wanted to study it in detail.
