The diffusion of Ammonia Gas

For my experiment, the factor that I am going to change is the angle of the tube. I will change the angle by 30º after each experiment, with 0º having the cotton wool at the top of the tube.

Prediction

I think that the gas will take a shorter period of time to turn the litmus paper blue if the ammonia is at the top of the tube because it has to travel downwards. It will take a longer period of time to turn the litmus paper blue if the ammonia is at the bottom because it will have to travel upwards.

Apparatus

Glass tube,

Ammonia solution,

Stand,

Boss,

Clamp,

Red litmus paper,

Cotton Wool,

Drawing pin,

2 Bungs,

Pipette.

Diagram

Method

Set-up the apparatus as shown in the diagram. Wet out five pieces of litmus paper and put them inside of the tube 4 cm apart. Put a bung on one end of the tube and on the other bung. Pin some cotton wool with 3 cm3 of ammonia solution on it with a drawing pin. Put this bung in the other end of the glass tube and start the timer. Record the time after each piece of litmus paper starts to go blue; this is to make sure that the time is measured fairly.

Wash everything out and set up the apparatus as before, so that the test is fair. Also to make sure it is fair use the same tube, the same size litmus paper and cotton wool, and the same amount of ammonia solution on the cotton wool.

Repeat this each time changing the angle at which the tube is positioned. Starting at 0º (The cotton wool at the top of the tube), change the angle by 30º each time, all the way round to 180º (The cotton wool at the bottom of the tube), recording all of your results.

Diagram

4 cm

8 cm

2 cm

6 cm

20 cm

0º

2

8

42

83

21

30º

2

20

47

87

44

60º

2

32

54

92

98

90º

2

28

55

36

243

20º

2

30

58

35

240

50º

2

30

58

35

236

80º

3

28

60

45

261

Conclusion

As the distance from the ammonia increases it takes a slower time to turn the litmus paper blue. This also occurs as the angle gets larger this is near enough the same for all of the distances but the 4 cm distance, this is because it is so close to the cotton wool that is soaked in ammonia solution. It takes a shorter time to turn the litmus paper blue when the angle is smaller because the ammonia solution on the cotton wool ran down the tube. This is where the experiment undermines my prediction but it can also support it as I said that it would take a longer time for the gas to diffuse upwards than it would downwards. Well this isn't true but I was correct on the timing of the ammonia gas as it did take longer to go upwards than it did o go downwards but for a different reason.

The energy of the gas comes from the amount of solution and concentration of the solution as the more solution of a higher concentration the more energy there will be.

Evaluation

I think that the experiment was accurate enough to obtain sufficient results to be successful. Although I do have some, anomalous this may be the temperature on the day, as I did not have time to do all of the experiments in the same day or not being able to recognise when they turn blue. I think that there is enough evidence to support my conclusion because I have 35 results (5 for each distance) and accurate enough distances amounts.

To improve the reliability of the experiment I could try to use the same size cotton wool every time. I could also use more litmus paper to get more results.

To extend this experiment I could try doing the same thing with a lower concentration or with less distance between the litmus paper. This can provide additional evidence because I can compare these results with the ones that I have now.