Ice melting is a process that involves heat transfer, phase changes and molecular movement. The more heat energy the ice absorbs, the faster it will melt. The surface on which the ice is placed also affects how quickly it will melt. Aluminum surfaces tend to absorb heat more efficiently than plastic, for example. In addition, the concentration and chemical makeup of the ice melt can also play a role in its speed of action, as can its temperature.
Sodium Chloride (rock salt) works by drawing heat from its surroundings to change the form of water molecules in ice. It disrupts the crystalline structure of ice and prevents it from reforming, making it a go-to option for managing icy surfaces.
As temperatures rise, the water molecules in ice vibrate, but they don’t move past one another very much because they are held together by hydrogen bonds. When the temperature reaches the melting point, 32oF (0oC), these bonds break down and the molecules become more dynamic, moving freely and forming a less structured state known as liquid water.
To demonstrate this concept, have students watch the video Ice Melting on Different Surfaces. Using the same type of ice, students should observe how ice melts differently on different surfaces, including asphalt and concrete. They can then use this information to predict where water will flow as it melts on a sidewalk or driveway in real life.
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