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Which makes better bubbles, skim milk or whole?
Tom Zinnen, UW Biotechnology Center
and UW-Extension, 608/265-2420,
zinnen@biotech.wisc.edu |
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(This is page two of a four-page sequence.
If you did not start with page one, please go back and start
with page one now) |
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How long should you blow bubbles? |
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The key is that you blow the same amount of time for each cup, and that
you blow just long enough to best see any differences in the amount of bubbles. |
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What do you mean by better bubbles? More bubbles?
Bigger bubbles? Clearer bubbles? |
All are fair questions that show that the original question really isn't
crafted well. One solution is to restate the question and then repeat the
experiment. This time you will be able to collect data with greater precision. |
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So, does milkfat affect bubblicity? |
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Do you have evidence that milkfat affects bubblicity? |
Do the two types of milk give identical or different bubbles? If they're
different, in what ways are they different? |
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How can you confirm that milkfat affects bubblicity? |
One way is to add milkfat to skim. In this "reconstruction experiment"
you add milkfat (in the form of cream) to skim milk and whole milk. |
You can then compare the bubble qualities of skim, of skim plus cream, of
whole, and of whole plus cream. |
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whole |
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How do you know you are blowing the same amount
of air through both straws? |
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How can you answer this question, just using the tools at hand?
- Switch and repeat: Switch the position of the two cups, so one time
the skim is on the left, and the next the whole is on the left. Do you
get the same amount of bubbles each time?
- Test the amount of air coming out of both straws: What are the possible
outcomes when you blow through 2 straws at the same time? Straw A could
get more air than straw B, straw B could get more air than straw A, or
straw A and straw B could get the same amount of air. What do you have
in front of you that could measure the amount of air?
- Expectations, Observations and Conclusions: What if you took 2 cups
and put equal amounts of skim milk in each cup? If you blow the same amount
of air through both straws, you expect to get the same amount of bubbles.
If you blow different amounts of air, you expect different amounts of bubbles.
Now, do the experiment and observe the bubbles. What do you conclude if
you get the same amount of bubbles? What do you conclude if you get different
amounts of bubbles?
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| You should also ask what's your "Batting Average?" If you blow
10 times into the two cups with the same type of milk, how often do you
get the same amount of bubbles from both straws? Is practice important in
science? |
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| What are other factors that could affect bubblicity? |
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Many people find that when they first compare skim and whole
milk, both bubble about the same. When they repeat the experiment
with the same milk samples 20 minutes later, skim bubbles but whole
milk won't! Can you list all the things the milk has been exposed
to during that 20 minutes? |
