A. Explain the significance of the given factors in your project design plan:
• Problem statement
• Relevance of your testable question
I have lived in a place that during the winter, ice would form on the streets and sidewalks and have wondered why things such as salt or sand are used over other methods to help de-ice the surfaces? Why is salt or sand the most commonly used substances when addressing this issue?
If you live in a place that gets cold in the winter, you've probably seen trucks out spreading a mixture of sand and salt on the streets after a snowfall to help de-ice the road. Have you ever wondered how this works? This basic chemistry project can give you some clues.
The goal of this project is to determine which added material will make ice melt fastest.
To make ice cream with an old-fashioned hand-crank machine, you need ice and rock salt to make the cream mixture cold enough to freeze. If you live in a cold climate, you've seen the trucks that salt and sand the streets after a snowfall to prevent ice from building up on the roads. In both of these instances, salt is acting to lower the freezing point of water.
For the ice cream maker, because the rock salt lowers the freezing point of the ice, the temperature of the ice/rock salt mixture can go below the normal freezing point of water. This makes it possible to freeze the ice cream mixture in the inner container of the ice cream machine. For the salt spread on streets in wintertime, the lowered freezing point means that snow and ice can melt even when the weather is below the normal freezing point of water. Both the ice cream maker and road salt are examples of freezing point depression.
Salt water is an example of a chemical solution. In a solution, there is a solvent (the water in this example), and a solute (the salt in this example). A molecule of the solute will
Bibliography: o Lachish, U., 2000. "Avogadro 's Number, Atomic and Molecular Weight," [accessed September 6, 2007] http://urila.tripod.com/mole.htm. o Furtsch, T.A., date unknown