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Homework Help: Shaving Cream in a Vacuum project

  1. Jan 30, 2005 #1
    Four our huge IB Group 4 science project, we are doing an experiment where we are placing different brands/types of shaving creams into a vacuum bell jar and measuring the expandability of each cream. Then we are having men test out the shaving creams, and seeing if the expandability of the shaving creams relates in any way to user satisfaction.
    Now, this is a random idea we thought of, but I'm having trouble finding out what in shaving cream causes it to expand....air trapped between molecules? but does anyone know what difference between shaving creams could cause one to expand more than the other? and what exactly does shaving cream do? does it provide a cushion between razor and skin?

    thanks to any comments!
  2. jcsd
  3. Jan 31, 2005 #2


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    shaving cream is a gas that is dissolved in a liquid.
    as you know, when you increase the pressure, gasses contract, and you can dissolve more gas into a liquid. Inside a can of shaving cream, you have alot of shaving cream packed in under high pressure, meaning that alot of gas (air probably, I dont exactly know what the gas is), is dissolved into the liquid, when you push the button and it shoots out, it exands, this is due to the relatively low pressure outside the can compared to the pressure inside the can, so some of the gas exans and excapes, this caused the shaving cream to expand.
    The same thing happens when you put shaving cream from normal "room" pressure into a vacume chamber, most/all of the gas excapes and expands the shaving cream alot. something similar can be seen by putting a marshmellow inside a vacume chamber, a marshmellow is a gas dissolved in a solid, the marshmelow will temporarily expand when all the gasses are rushing out, but then it colapses under its own weight because there is nothing to hold it up.
  4. Jan 31, 2005 #3
    Thanks for the help Mrjeffy,
    I was also wondering if anyone knew exactly what shaving cream does when you shave? lubricant? cushion?
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