SCREAMING for Ice Cream

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SCREAMING for Ice Cream

• Freezing Point Depression
• Course Making Physics Fun
• Facilitator Robbie E. Foxx, Ph.D.
• beauty66_at_bellsouth.net
• Date June 28, 2006

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Mississippi Science Framework Competency 8th
Grade Level

• 8. Analyze the properties of matter. (P)
• Objectives
• a. Determine experimentally physical and
  chemical properties including density,
  conductivity, and reactions with water, acids,
  and bases.
• c. Write simple formulas for compounds
• 10. Investigate the transfer of energy. (P)
• Objectives
• a. Measure the transfer of heat between
• two objects using the Celsius scale.
• c. Research and discuss energy transformation
• d. Convert one energy form to another.
• (objectives are lettered per the MS Science
  Framework)
• 
  

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Engage

• http//www.bbc.co.uk/schools/gcsebitesize/chemistr
  y/chemicalreactions/2energychangesrev2.shtml

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Engage

• Lets look at an endothermic reaction. Ammonium
  thiocyanate is mixed with barium hydroxide. The
  mixture is stirred and the two solids react. A
  slush is formed because water is one of the
  products of the reaction.

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Engage
Here we see a drop of water is being placed on a
block of wood and the beaker is placed on the
water drop. STOP Make a hypothesis as to how the
beaker will be affected when placed on top of the
wooden block.
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Engage
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The Scientific Method

• Title
• Statement of the Problem
• Hypothesis
• Materials
• Procedure
• Results (data)
• Conclusion

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Thermochemistry Prerequisites

• Energy Transfer Movement of energy from one
  place to another or from one substance to
  another, or the conversion of energy from one
  form to another
• The Law of Conservation of Energy The amount of
  energy that exists today is the same as the
  amount of energy that existed thousands and
  millions of years ago. The energy in use today
  existed ages ago but was stored in some
  concentrated form like a high energy bond.
• Melting, boiling and evaporation are all
  endothermic processes (not reactions).

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Examples of Endothermic and Exothermic Reactions.

• Most reactions are exothermic.Examples are
• 1) Combustion of methane (natural gas).
• Few reactions are endothermic.Examples are
• 1) Photosynthesis.Chlorophyll is a very clever
  catalyst,which allows plants to make sugar from
  carbon dioxide in the air.The energy needed for
  the reaction comes from sunlight.
• 2) The reaction of ethanoic acid with sodium
  carbonate.
• 3) Dissolving some salts in water is an
  endothermic process.Potassium chloride and
  ammonium nitrateboth take in energy when they
  dissolve.If you put a thermometer in the
  solution as they are dissolving,you will see
  that the temperature drops.
• 4) Melting, boiling and evaporationare all
  endothermic processes (not reactions).

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Prerequisites

• Energy Transfer Movement of energy from one
  place to another or from one substance to
  another, or the conversion of energy from one
  form to another
• Energy of Reaction Energy released or absorbed
  during a chemical reaction, part of the energy
  transfer that takes place. In a chemical equation
  it may be represented by the symbol ?H. In a
  chemical reaction, the energy stored in the
  reacting molecules is rarely the same as that
  stored in the product molecules.
• Depending on which is the greater, energy is
  either released (an exothermic reaction) or
  absorbed (an endothermic reaction) from the
  surroundings. The amount of energy released

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Prerequisites

• Exothermic Reactions These are reactions that
  transfer energy to the surroundings. The energy
  is usually transferred as heat energy, causing
  the reaction mixture and its surrounding to get
  hotter.
• Question What are some examples of exothermic
  reactions?

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Answer

• Burning
• Neutralization reactions between acids and
  alkalis
• The reaction between water and calcium oxide

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Prerequisites

• Endothermic reactions These are reactions that
  take in energy from the surroundings. The energy
  is usually transferred as heat energy, causing
  the reaction mixture and its surroundings to get
  colder.
• Question How can the temperature decrease be
  detected?

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Answer

• By using a thermometer
• Question what are some examples of endothermic
  reactions?
• Possible Answers
• Electrolysis
• An example of an endothermic chemical reaction is
  photosynthesis. During photosynthesis, plants use
  the energy from the sun to convert carbon dioxide
  and water into glucose and oxygen. The reaction
  requires 15MJ of energy (sunlight) for every
  kilogram of glucose that is produced
• sunlight 6CO2 (g) H2O(I)C6H12O6 (aq) 602
  (g)

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Heat Changes During Chemical Reactions

• Exothermic reactions release energy. The energy
  released by the bonds formed in products is
  greater than the energy needed to break bonds in
  reactants.
• Endothermic reactions take in energy. The energy
  required to break bonds in reactants is more than
  the energy released by the bonds formed in
  products.
• Every reaction can be written in the reverse
  sense. The energy changes for the forward and
  reverse reactions have the same numerical value
  but opposite signs.
• http//www.800mainstreet.com

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Thank you for your participation and for being a
great class!!!!