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Ice Cream 20091205 (student preso)
 

Ice Cream 20091205 (student preso)

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student presentation

student presentation
general physics
5 dec 2009

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    Ice Cream 20091205 (student preso) Ice Cream 20091205 (student preso) Presentation Transcript

    • The Physics of Ice-cream
      Napat
      Peerada
    • How to make ice-cream?
      Put syrup and water into the small cup/bag
      Put ice and salt into the big cup/bag
      Put the smaller bag into the bigger bag
      Shake until the ingredients in the smaller bag freezes
    • Water
      At 0 °C, melting point of ice and freezing point of water
      The ice molecules are constantly escaping to water, and the water molecules are captured at the surface of ice.
      This equilibrium will be maintained as long as the temperature is kept at 0°C and there is no external interruption
    • Salt
      Salt decreases the freezing point
      Salt molecules disrupt the equilibrium
      Even though salt molecules are dissolved in water, they do not easily attached to the ice.
      This means that the number of water molecules able to captured by ice goes down, so the rate of freezing goes down as well
      At the same time, the rate of melting of ice is unchanged, so melting occur faster than freezing
    • Salt
      To return to equilibrium, the temperature must be lower to make the water molecules slow down and attached to the ice more.
      The higher the concentration of salt, the lower the freezing point drops.
    • What about sugar in the syrup?
      Temperature of the larger container has decreased: the inside decreases as well
      Sugar does not disperse into ice, only in water
      As water freezes out, the remaining sugar solution become more concentrated, making it harder for water to crystallize in its pure form.
      The temperature is further lowered, the equilibrium shifted and the freezing point has decreased
    • Ice-cream freezing curve
      Not all of the water is frozen!
      The rest remain as very concentrated sugar solution
    • Freezing-Point Depression
      ΔTf = Kfcm
      Kf : freezing point depression constant
      Cm : molar concentration
    • Task
      Peerada
      Introduction
      Salt and water
      Napat
      Sugar and water
      Freezing point depression
      Conclusion
    • References
      http://books.google.co.th/books?id=bKZ1oICZWywC&dq=the+science+of+ice+cream&printsec=frontcover&source=bl&ots=BOF8B945rQ&sig=cdjqNFX_zUvCdIpGvRr7Yjw3_r0&hl=en&ei=4UEXS_jaNNGHkAWUl-HkAw&sa=X&oi=book_result&ct=result&resnum=6&ved=0CCIQ6AEwBQ#v=onepage&q=&f=false
      http://www.worsleyschool.net/science/files/saltandfreezing/ofwater.html
      ://www.foodsci.uoguelph.ca/dairyedu/icstructure.html
      http://hyperphysics.phy-astr.gsu.edu/hbasees/Chemical/meltpt.html
      http://www.chemguide.co.uk/physical/phaseeqia/raoultnonvol.html