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In many experiments you have seen or done, you may have observed an increase in temperature. Heat energy is often associated with chemical changes.

Heat energy is also associated with some physical changes. For example, you need to add heat to water in order to get it to boil. On a previous Sci-ber text page, you experimented with heating ice until you were able to get it to boil.

Now it is time for you to remove heat energy and observe changes. You should make careful observations to determine what physical and/or chemical changes you observe.

This activity will provide enough ice cream for about 4 people. Find some friends and have some fun!

 

Materials:

  • Two quart size zip closure bags
  • Two gallon size zip closure bags
  • One pint half & half
  • 1/4 c. sugar
  • 1/2 t. vanilla
  • 1/2 t. salt
  • Ice
  • Rock salt
  • Gloves (optional)
  • Bowls
  • Spoons
  • Toppings (optional)
 
Safety concerns: Be sure to keep all chemical safety rules. As with all science lab activities, the most important safety rule is to follow all teacher directions.
 

Procedure:

  1. Carefully open one of the quart size bags.
    • Pour in the half & half.
    • Add the sugar, vanilla, and 1/2 t. salt.
    • Squeeze as much air out as you can then zip the bag closed.
    • Carefully squeeze the bag back and forth to mix the ingredients.
  2. Carefully open the second quart size bag and place the first bag inside.
    • Squeeze out as much air as you can and close the outer quart size bag.
  3. Carefully open one of the gallon size bags.
    • Fill this gallon size bag about 1/4 full of ice
    • Determine how much rock salt you are going to add and record this number.
    • Place your two quart size bags onto the ice and rock salt.
    • Add more ice on top of your quart size bags until the gallon size bag is about 3/4 full.
    • Determine how much more rock salt you are going to add and record this number.
    • Squeeze out as much air as you can and close the gallon size bag.
  4. Carefully open the second gallon size bag and place the first gallon size bag inside.
    • Squeeze out any excess air and then zip the outer bag closed.
  5. Gently use your hands (use gloves if you want) to move the ice and rock salt around the quart size internal bags.
  6. Keep track of how long it takes for the inner bag ingredients to change from liquid to solid.
  7. Carefully remove the bag with your ingredients in it.
    • Open and enjoy your product!
    • Place material for each person in a separate bowl and add any desired toppings.
 

Data:

  • Total amount of rock salt added ______________________.
  • Time until inner materials changed from liquid to solid ______________________.
 
In your science journal, record the amount of rock salt you used and the time it took to change the materials to a solid. Collect the same data from the other groups who did this experiment.
 

Analysis:

  1. What evidence of physical changes did you observe?
  2. What evidence of chemical changes did you observe?
  3. Why was the rock salt added to the ice?
  4. What changes did you observe in the outer bag (filled with rock salt and ice?)
  5. How would you describe the changes you observed in the inner-most bag?
  6. Did you add or remove energy from the materials in the inner-most bag?
    • What evidence do you have to support this answer?
  7. How did the amount of rock salt used affect the time it took to change the liquid to a solid?
  8. How did the amount of rock salt you used compare with that used by other groups?

Review Science safetey rules here.

Get the plug-ins: Get Adobe Acrobat Reader , and Get Quicktime Player. (The QuickTime plug-in is needed to play sounds and movies correctly.)

Want to share photos of you or your friends doing this activity? Send it in an e-mail with the following information:

  1. The title of the activity
  2. The URL (Internet address)
  3. Your name.

Remember that no pictures can be used that show student faces or student names on it. 

Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE 8th grade science core.


Updated October 24, 2008 by: Glen Westbroek

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