Friday, October 16, 2009

Kitchen Chemistry

On a school day off this week, 25 third through fifth graders participated in our 1st ever Hands-On Science program applying the scientific method to learn about science in the kitchen! But don't be fooled- having your kitchen as a laboratory is a lot of fun and a great way to enjoy exploring science! Here are two projects we did that you can try at home and consume the results!

How to make ice cream without a freezer?
1 gallon size zip-loc bag
1 quart size zip-log bag
1 T sugar
1/2 t vanilla extract
1/2 cup whole milk or cream
6 T rock salt (kosher salt)
2 cups of ice
Place sugar, vanilla and milk in the quart size bag. Tightly seal the bag. Place the bag into the gallon size bag and pack with ice until it is half full. Pour the salt onto the ice and tightly seal. Check for any leaks. Shake the bags for 5- 10 minutes until the ingredients in the small bag are softly frozen. Remove the small bag and empty into a bowl. Enjoy!
How Does it Work?:
Just like we use salt on the roads in winter, salt causes ice to melt. Water normally freezes at 32 degrees F, but when salt is added, the freezing point of water becomes lower. Because the freezing point of milk is lower than of ice, by lowering the temperature around the milk, we are able to create an environment in which the temperature is lower than 32 degress and in which the milk mixture can freeze into ice cream.

How to carbonate homemade root beer?
large plastic container, wooden spoon, plastic laddle, sacle, think rubber/latex gloves
2 gallons of cold water
2 lbs of sugar
2 lbs. of dry ice (HANDLE WITH CARE:dry ice is so cold it can cause burns-wear gloves if directly handling it)
2 oz. of root beer extract
Pour 2 gallons of water into container and add sugar and stir until sugar is dissolved. Add root bear extract and stir again. Put on the gloves and add dry ice in chunks one at a time, stirring. Cover loosely and stir occasionally for 1/2 hour until all dry ice has turned into gas.
How Does it Work?:
Dry ice is solid carbon dioxide. The dry ice changes from a solid phase straight into a gas phase of carbon dioxide under standard pressure and temperature. This change from a solid to gas phase is called sublimation because it skips the liquid phase (just like boiling is the change from a liquid to gas phase). When dry ice is placed in water, sublimation accelerates and the dry ice vaporizes into a clear colorless gas more quickly than in air (you will see the cardon dioxide gas bubbles slow down as the temperature of the water cools). The white vapor/fog is carbon dioxide gas and water vapor which is the water in the air that is condensing (as it cools from the dry ice) into tiny droplets.

For additional ideas, try these activities from Scholastic's The Magic School Bus, each focusing on a different science concept and the PBS show, Zoom, that features a virtual kitchen (no mess to clean up).

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