![]() If any of the ice cubes no longer form a triangular shape in their bowl, gently nudge the ice cubes to make a triangle again. Move each bowl to an empty shelf in the refrigerator.Sprinkle salt, sugar, sand, or nothing over the ice cubes in each bowl. Optional: Masking tape and a permanent marker for labeling the bowlsįigure 3.Alternatively you could use a funnel that fits in the graduated cylinder. Large cup with a spout, such as some measuring cups.50 mL graduated cylinder, or smaller size.You will want an empty shelf that can hold all four bowls, unstacked, at the same time. They should all be the same size and shape. Science Buddies' recommended supplies for this project can be found at Department of Chemistry, Iowa State University. Boiling-Point Elevation and Freezing-Point Depression. To try a simulated experiment on freezing point depression or boiling point elevation, see this resource (note that it is a Flash animation that requires browser plug-in): ![]() Avogadro's Number, Atomic and Molecular Weight. Retrieved September 6, 2007.įor information on Avogadro's number and molecular weight, see: HyperPhysics, Department of Physics and Astronomy, Georgia State University. Which of the suggested test substances are insoluble in water?įor more information on colligative properties, see:.Which of the suggested test substances are soluble in water?.What is freezing point depression? When does it happen?.Which substances will speed up the melting of the ice? You will test substances that dissolve in water (i.e., soluble substances), like salt and sugar, as well as a substance that does not dissolve in water (i.e., an insoluble substance), specifically sand. In this science project, you will investigate different substances to see how they affect the rate at which ice cubes melt. This is an example of a colligative property. The amount by which the freezing point is lowered depends only on the number of molecules dissolved, not on their chemical nature. Other substances when mixed with water can also lower its freezing point. This is why there is a greater attraction between the water molecules and the molecules of salt than there is between the molecules of salt by themselves, and why the water can dissolve the salt to create a salty solution. Sodium (Na +) and chloride (Cl -) ions that make up table salt. ![]() (This polarization is caused by the distribution of electrons in the water molecule specifically, its hydrogen ends have a partial positive charge, and the oxygen end has a partial negative charge.) Because water molecules are partially polarized, it is possible for them to arrange themselves around ions (which are molecules or atoms that have a charge), like the Water (H 2O) is a good solvent because it is partially polarized. A molecule of the solute dissolves (goes into solution) because the force of attraction between the solute molecule and the solvent molecules is greater than the force of attraction between the molecules of the solute. In a solution, there is a solvent (the water in this example), and a solute (the salt in this example). ![]() ![]() Table salt (technically sodium chloride, or NaCl) when mixed with water is an example of a chemical solution. Both the ice cream maker and road salt are examples of freezing point depression. 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. This makes it possible to freeze the ice cream mixture in the inner container of the ice cream machine. In both of these instances, salt is acting to lower the freezing point of water, and changing what phase of matter the water is (i.e., turning solid ice into liquid water).įor 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. Similarly, if you live in a cold climate, you have seen the trucks that salt and sand the streets after a snowfall to prevent ice from building up on the roads. If you have ever made homemade ice cream the old-fashioned way using a hand-crank machine, you probably know that you need ice and rock salt to make the cream mixture cold enough to freeze. ![]()
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