Comparing the density of skimmed milk and homogenised milk

Analysing

From performing the experiment I have found that skimmed milk is less dense then homogenised milk. I say this because from the results I have obtained show that the 5 drops of skimmed milk that I released into the 100ml measuring cylinder fell to the 10ml mark at about 10 seconds slower than the 5 homogenised milk drops. So this suggests that homogenised milk is denser the skimmed milk.

My initial thoughts when doing the experiment was that I thought that the homogenised milk would be the denser out of the two as it contained a lot more fat and from performing the experiment I found that this was the case and that the homogenised milk was the most dense. So I have come to the conclusion that it is the fat in the milk that makes it dense. This is proven in my results as the skimmed milk dropped to the 10ml mark slower because it contains more proteins, which are lighter making the drop fall slower, than the homogenised milk which has more fats, as these are heavier and make the drop fall faster.

To support my conclusion I have performed the student T test on my results and they turned out to be highly significant. So these results are good enough to support the conclusion I have drawn.

Evaluating

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To support my conclusion I have performed the student T test on my results and they turned out to be highly significant. So these results are good enough to support the conclusion I have drawn.

Evaluating

After performing the experiment I didn’t think the experiment was very accurate as I got 4 anomalous results i.e. drops 1 and 5 from the skimmed milk and drops 2 and 5 from the homogenised milk we’re all at least 5 seconds apart from the other results. The reasons for this may have been because you could not get the drop of milk to be the same density each time as it was very difficult to be accurate with the 1cm syringes that we were using. As if you had the slightest twitch a lot more milk would be released. Also some of the drops separated meaning that some drops we’re getting to the bottom quicker.

The limitations of the experiment were that I was limited to the syringes, as, if I could have had a bigger syringe there would have been a better chance of getting an equal size drop each time, as it would have compensated for human error. Also the timing was inaccurate, as a few times I only just started the clock before the drop reached the 100ml mark. So if I had a bigger volumed measuring cylinder I would have more time to drop the milk and then get into position to start the timing. Furthermore I was limited to the timing equipment, as the stopwatch method doesn’t compensate for human error. So if I had could have used a computer I would have had a more accurate device for timing, for instance when the drop broke a beam of light at the 100ml mark the timing would start and then when the drop passed through another light beam at the 10ml mark the timing would stop. Finally the last limitation was the time as if I had more time I could have kept repeating the experiment until I got 5 equal drops instead of some dispersing.

The main source of error I found was when using the stopwatch as the drops separated so I didn’t know weather to stop the clock when the first part of the drop past the line or when each bit of the drop passed the line. I decided to stop the clock when the first part passed the 10ml line. However this could have been a main reason for the anomalous results as this meant some drops we’re unequal meaning some we’re more dense than others, so this wasn’t a fair test.

If I had to do the test again I would make a few modifications to the experiment I performed. These amendments would be:

Use a larger syringe so that there would be less chance of error as it would be easier to get the same sized drops making my results more accurate.

A larger volume measuring cylinder so that I have more time to release the drop and then start the stopwatch before the drop passes the 100ml mark. This is to make my results more precise.

Stopping the clock after the whole of the drop had passed the 10ml mark, this is so that if the drops did disperse I’d still be timing the whole drop to pass the mark or to be more accurate I would keep doing the drop until I got 5 drops that didn’t disperse but I didn’t have time for that.

Using a computer to do the timing, as this would be a lot more accurate as there wouldn’t be human error affecting the result.

I could also try semi-skimmed milk, if I was going to take this experiment in to more detail, to see if the results from that followed my conclusion and this would also give me more evidence to support my conclusion. I would expect the drops of semi skimmed milk to drop slower than homogenised milk but quicker than skimmed milk. As it has more proteins than homogenised milk but more fats than skimmed milk.

I could have expanded my experiment by finding out if the size of the drops made a difference, as this would again add more evidence to support my conclusion.

It is important to clear all of these problems in the experiment as they reduce the accuracy and the reliability of my results that obtained, but the main change I would make would be to have more time so I could keep repeating the drops until I got 5 of the same size so that it was a fair test. However still I believe the results I got from the experiment support my conclusion but they still need to be improved.