Can you Change the Freezing Point of Water?

Water freezes (from a liquid to a solid) at 32 degrees F. or 0 degrees C.

Challenge the students to think of a substance that could be added to the water (before or after it freezes) to LOWER the freezing point of water.

Hint: What do we add to our streets and sidewalks to prevent them from freezing or refreezing in the cold winter months if we live in cold snowy climates? (salt, rock salt, etc.)

Activity: Can you pick up a piece of ice with a string?

Materials:

• plate 
• ice cube
• piece of string
• salt

Directions

• Place the ice cube on a plate or table.
• Have students try to pick up the ice cube with the string.
• Place the string over the ice cube and pour a small amount of SALT over the string.
• Wait 15 seconds.
• Observe what happens to the ice cube.
• Try to pick up the ice cube.

Explanation

• The salt lowers the freezing point of the ice and it starts to melt. Then as the ice melts and dilutes the salt solution the water refreezes with the string in the ice.

• This is why salt is scattered on icy roads and walkways to make the ice melt.