How Heat Affects the Speed of a Chemical Reaction

I know when the reaction is completed when the cross on which the beaker containing the reactants disappears due to the increasing cloud of precipitate. To ensure accuracy I will be repeating the experiment a number of times.

This equation depicts my experiment.

FAIR TEST

I have made sure in all of my experiments that is has been a fair test.

To do this I have used exactly the same amount of reactants (25ml of thiosulphate and 5ml of hydrochloric acid). I make sure that the amounts are the same by using a measuring cylinder on a flat surface and a stop clock is used in every test guaranteeing that the times are precise.

I have also made sure that all of the temperatures were the same.

The temperatures were as follows:

* 20

* 30

* 40

* 50

* 60

* 70

On top of those precautions, I repeat my results twice.

PILOT WORK

The pilot work can be classed as a practise before we began to embark on the experimentation properly.

I performed the experiment on only three temperatures. Here are the results:

TEMPERATURE

RESULTS

20

1 SECONDS

40

3 SECONDS

60

0.7 SECONDS

Looking at the pilot work, I have chosen the temperatures between 20 - 70 in 10 degree intervals. I decided to stop at 70 because any rates of reaction after that would be too quick and to start before 20, then the rate of reaction would be too slow.

METHOD

* I filled two beakers. One containing sodium thiosulphate and the other hydrochloric acid.

* Over the Bunsen burner, I separately heated the solutions to the desired temperature.

* When both were at the correct temperature, I added both together into a different beaker and placed this beaker on the cross, whilst simultaneously starting the timer.

* I stopped the timer once the black cross had fully disappeared because of the cloudy precipitate.

RESULTS

TEMPERATURE

RESULT 1

RESULT 2

20

2 MINUTES 20 SECS

2 MINUTES 26 SECS

30

2 MINUTES

2 MINUTES 2 SECS

40

50 SECOND

52 SECONDS

50

36 SECONDS

30 SECONDS

60

5 SECONDS

7 SECONDS

70

8 SECONDS

0 SECONDS

There are no abnormal results, as you can see from my table so I think the experiments went well.

AVERAGING RESULTS

TEMPERATURE

RESULT 1 AND 2

AVERAGE

20

2.20 + 2..26

2.2

30

2 + 2.2

2

40

50 + 52

51

50

36 + 30

33

60

5 + 17

1

70

8 + 10

9

ANALYSIS

Looking back on my aim, prediction and scientific knowledge, I can fairly say that I proved correct and that a higher temperature does indeed increase the rate of reaction. The kinetic theory proved to be correct which says that the higher the temperature causes that particles begin to move and vibrate leading up to them colliding because we have given them more energy, we call this a chemical reaction. My results support all of my planning and researching.

The two graphs I have produced, showing the rate of reaction supports my predictions too.

EVALUATION

To have made my experiment better, I could have used a wider beaker. This would have made the experiment easier to witness but I do believe that if you increase the surface area, then you can increase the rate of reaction. Repeating the experiment would have also made more sure results.

Another way of ensuring precision is if I had used an electronic water bath where then I could have made the temperature exact.

Apart from welcome improvisations, I believe that my experiment went without difficulty and only minor problems were encountered. The main problem was that the solutions were not being cleaned well enough after one temperature. I also mixed the beakers a few times so twice a standing beaker with sodium thiosulphate or hydrochloric acid would begin to turn cloudy even before the mixing process had begun. Otherwise the experiment went according to plan, however think there would have been minor in corrections because there is no doubt I didn't pinpoint the exact moment that the black cross disappeared.

I can conclude that there were no anomalous results, and I don't think there would be any outstanding variations in results, should I have repeated the experiment further.

MARYAM HASSAN

MRS BOWMAN

CHEMISTRY