1. Liquid Nitrogen Ice Cream!
Liquid nitrogen is used to freeze a large batch of ice cream for student consumption
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2. Purpose To understand the properties of a liquified gas
To make an edible dessert in a novel way
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3. Demonstration
The liquid nitrogen adsorbed the heat from the cream mixture
As it did so, the liquid nitrogen boiled off taking the heat into the atmosphere
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4. Concepts 1. Biological Molecules 2. Thermodynamics 3. Cryogens
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5. 1. Biological Molecules
Biological Molecules are those commonly found in all living organisms
Biological molecules
Constitute the organism and nourish the organism
Milk contains all the three most important biological classes of molecules:
Lipids (which are the same as fats and oils)
Proteins
Carbohydrates (which include all sugars)
Milk contains
Lipid: Milkfat
Protein: Casein Carbohydrates: Lactose (milk sugar)
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6. 2. Thermodynamics
Thermodynamics is the study of heat and energy changes
The heat in a substance reflects the speed the molecules of the substance are moving
The molecules in cream move faster than those in liquid nitrogen, therefore the liquid nitrogen is colder
When the cream and liquid nitrogen are mixed the heat in the cream is transferred to the liquid nitrogen, causing the liquid nitrogen to warm above its boiling point and boil away
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7. 3. Cryogens A cryogen is a substance used to cool other substances
Liquid nitrogen is nitrogen gas from the atmosphere in which the molecules of N2 have been pressed together using pressure
Liquid nitrogen boils away to gas at – Degrees Celsius
Way Below Room Temperature which is 25 degrees Celsius!
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8. Conclusions
A mixture containing the major three kinds of biological molecules will transfer the motion of those molecules to a cryogen
The heat therefore moves from the mixture into the cryogen
The cryogen will boil away as it absorbs the heat while the mixture will simultaneously cool and freeze
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9. Comments
The recipe for this ice cream is 4 quarts heavy cream 4 quarts half-and-half (50% milk and 50% cream) 1 cup sugar 3 tablespoons vanilla extract 1 package of M&M candy
The liquid nitrogen is not cheap! It costs approximately $40 to make 10 gallons of ice cream!
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