Salt Melting Ice

Grade Level: 4th -  6th; Type: Chemistry

Objective:

In this experiment, students will discover how and which salt melts ice the quickest. Students are responsible to uncover the chemical reactions that take place between the molecules of salt and ice.

Research Questions:

• What happens when salt contacts ice? What happens to the molecules?
• What is each kind of salt in this experiment made of?

Ice is created when water is frozen past the freezing point which is 0ºC or 32ºF, under normal conditions. When water freezes, the particles are tightly packed together and are more stationary than in the liquid state. It is now a solid rather than a liquid.

It is said that salt melts ice because it lowers the freezing temperature from it and disrupts its molecular equilibrium. But there are different kinds of salt containing different molecular compositions and elemental concentrations.

Materials:

Ingredients

• Salt
  • Regular Table Salt
  • Kosher Salt
  • Epsom Salt
  • Rock Salt
• 5 Blocks of Ice

Equipment

• Clear plastic containers/ boxes big enough to hold the blocks of ice

Extras

• Pen and paper

Experimental Procedure:

1. If you don't have blocks of ice ready-bought, then your first step should be to pop some water into the freezer and to make the ice. They should be approximately the same size.
2. Once you have the ice ready set them in separate clear plastic containers, side by side. Label these containers with the kind of salt that will be added to it.
3. Sprinkle an even amount of each kind of salt in each separate container. Now, you'll just have to wait to see what happens! 10-minute intervals are good times to check on the ice.
4. Observe the progress of the melting ice and record your findings until all the ice has melted.
5. Record your results. How fast did it take for all the ice to melt out of each container?

Terms/Concepts: Water; Ice; Molecular composition; Salt; Freezing temperature; Melting temperature

References:

A Drop of Water by Walter Wick (1997). Scholastic Press.

Braun, Charles L.; Sergei N. Smirnov (1993). "Why is water blue?"

J. Chem. Educ. 70 (8): 612. http://www.dartmouth.edu/~etrnsfer/water.htm

Lide, D. R. (Ed.) (1990). CRC Handbook of Chemistry and Physics (70th Edn.). Boca Raton (FL):CRC Press.