The subdivision:
Smaller pieces will be reacts faster cause it has large surface area make they can have more collisions
Planning
In this experiment, we will only change the temperature of the solution to see how it affects the rate of the reaction. So this time, I will make the amount of sodium thiosulphate and acid be the same. And mix them together and measure the time of the reaction.
In the experiment, I will use the bench hydrochloric acid and a solution of sodium thiosulphate which is concentration is 8 grams per dm³.
Before do this experiment, we need to heat the sodium thiosulphate before mix with the hydrochloric acid. And I plan to make 15 different temperatures of the sodium thiosulphate. They are from 15℃ to 85℃. Every 5℃ to do experiment once.
And when them reacted they will turn to milky, we will use stop watch to measure the period of time since mix it to it turn to milky
Before I do the real experiment in my course work, I do an experiment first. I do it in 20℃(the room temperature), 43℃, 87℃.
So, now I can see that if I put them together, they will turn milky
Apparatus
- Stop watch
- Scrap paper with a cross
- Bunsen burner
- Tripod
- Heatproof mat
- gauze
- sodium thiosulphate
- hydrochloric acid
- thermometer
- conical flask
- beaker
-
measuring cylinder(25 cm³and 10 cm³)
Methods
- I draw a cross on the scrap paper
- I measure 25 ml of sodium thiosulphate carefully
- put 25 ml of sodium thiosulphate in to a beaker and put it on the tripod and also put a thermometer in the beaker to measure the temperature.
-
turn on the Bunsen burner and look at the thermometer carefully. Wait until the sodium thiosulphate to 85℃
- when the sodium thiosulphate is heating, measure 10ml of hydrochloric acid by the measuring cylinder, then put it into the conical flask.
- put a conical flask on the scrap paper with cross
- after heated it to the planned temperature, put the hot sodium thiosulphate into the conical flask, and start the stop watch.
- let it mix with the hydrochloric acid, look at the cross through the flask carefully.
- wait the solution turn to milky, and until can’t see the cross then stop the stop watch.
-
record the time it take and repeat above step to do the experiment against, but the temperature of the sodium thiosulphate will be less 5 degree every time until 15℃.
Result
There are the result of my experiment(first time):
The second time result:
The average of two experiment:
After I do the experiment, I find out if the temperature of sodium thiosulphate higher, the reaction will take shorter time, that mean the reaction will be faster. And my experiment result goes very well.
The graph of two experiment result and the average:
Value for the rate of the reaction
The equation :
1
Time in sec-1
The value for the rate of the reaction of first time experiment:
The value for the rate of the reaction of second time experiment:
The value for the rate of the reaction of the average of the experiment:
Conclusion
In this experiment result, if the temperature of sodium thiosulphate higher, it takes shorter time to react with hydrochloride acid to turn to milky. That mean if the temperature is higher, it reacts faster. They react faster because of the higher temperature give more energy to the particles and let them have more frequent collision and break down the chemical bonds. It have more frequent collision cause they move more quickly. The particles move quickly let the reaction faster.
In the result of the first experiment;
In 15℃ and 85℃ sodium thiosulphate( heat before mix with the acid). In 15℃ take 201sec to reaction, but 85℃ just take 6sec to reaction. In here, show that the higher temperature (85℃) take shorter time to react. This result of the experiment show my prediction is right.
Evaluation
Most of my experiment result gone very well, because I measure my amount of the solution is very accuracy, and I control the temperature of the sodium thiosulphate very carefully. But just one result in my first experiment in 45℃, it should be shorter for few sec. The other result are all right.
On the other side, I also find some difficult when I doing the experiment. Such as, when I mix that two solution, I can only use the thermometer or use my hands to shake the flask to help to mix it. So I think, next time I do the experiment I will use a glass rod to help to mix it.
And when the sodium thiosulphate in the room temperature is 20℃, so I need to use ice with cold water in a big bowl and put the beaker of sodium thiosulphate to make it cold until 15℃.
Also, when the temperature of sodium thiosulphate is low( in 15℃ -25℃), it take ages to react. But the time let me to do the experiment is not enough. So I mix two different temperature sodium thiosulphate with acid at the same time. So I need two sets of equipment for make I can do this experiment on time.
In this time, because I have enough data, I can’t calculate how does the reaction slow down and stop. I need more data to calculate this. So if I do the experiment next time, I will also measure the temperature of the solution when it reacting and when does it stop to change. The reaction stop because of all the solution has reacted.
If I get the temperature when it is reacting, I can also calculate the speed of the reaction.