To find out if concentration affects the rate of diffusion.

Independent variable: We are changing the molar of hydrochloric acid we are adding to the gelatine cubes. The molars range from 1-3.

Apparatus:

• 1 measuring cylinder
• 1 test tube
• 1 stop clock
• A large gelatine cube containing indicator and NaOH
• Hydrochloric acid ranging from 1-3 molars
• A scalpel

Diagram:

Method:

• Take the large gelatine cube and cut into 15 equal pieces
• Place on piece of the cube into the test tube
• Measure out 10mls of HCl in the measuring cylinder
• Pour the HCl into the test tube with the gelatine cube and start the clock
• Time how long it takes for the pink colour inside the gelatine cube to completely disappear
• You will also notice that the cube dissolves slightly
• Record your results and repeat this same process 3 times for each molar of acid:

• 1 molar
• 1.5 molar
• 2 molar
• 2.5 molar
• 3 molar

Fair test: To ensure that this experiment is a fair test I will take a number of precautions:

• Ensure that all the gelatine cubes are the same size so that the time taken for is accurate
• Ensure that the acid is measured out to exactly 10mls each time to keep it fair
• Use the same equipment each time so there are no variations

Safety: To make sure that this experiment is safe you should wear safety goggles so as not get and HCl into your eyes at it is highly corrosive and irritant. You should also tuck your tie into your shirt so that it does not hang into the HCl or any other part of the equipment or apparatus. Make sure you have a clear working area so that no accidents occur whilst you are conducting your investigation. There is no Bunsen burner or any other dangerous equipment in involved in this investigation apart form the HCl therefore there are not many safety precautions.

Results Table:

Conclusion: As you can see my results are very different to what I have predicted. Although my prediction was correct the results disproved it and there seem to be a lot of anomalies within them. I you look at graph you can see that the line is all over the place. The results should have looked a little more like this:

This graph shows a clear line where the time taken for diffusion to occur is going down. This is what was supposed to have happened when conducting our experiment however this was not the case. The prediction I made was the same as this graph and this is how I expected our results to turn out, as 3 molar acid is much stronger than 1 molar for example.

Evaluation: I think that when we were conducting our experiment we followed all the precaution and instruction given pretty much to a T. I am fairly confused about the results that we have ended up with but I think that they may have turned out this way because one, we had to conduct the investigation over a period of two days as each of the 15 goes took up to 10 minutes and we needed clearing away and preparation time. Therefore we had to use several different pieces of equipment maybe this had an effect on the unusual results. The first day of the investigation the cubes had been placed in a fridge overnight and on the second day this hadn’t been done which I think had the biggest effect on our results. If I were to conduct the investigation again I would have liked to have gotten some more usual results and be more in line with my prediction. This is the first time my results have been this unreliable and unusual and next time I will ensure that I follow everything exactly to ensure the results are good and reliable.

Graph: