A Salty Solution

Do you know why people put salt on roads and sidewalks during icy weather? Does the salt provide traction for cars and for people? Or is there another reason? In this activity, you can learn what happens when salt combines with ice.

Materials

ALT

Procedure

Use masking tape to label the two freezer-safe containers. Label one container “Water Only,” and label the other container “Water and Salt.” Pour 1 cup water into each container. For the container labeled “Water and Salt,” dissolve 2 teaspoons salt in the water. Put both containers in the freezer. Check the containers every 15 minutes. Make a note of which contents freeze first. If a thermometer is available, take the temperature of the “Water and Salt” solution as it begins to freeze.

Results

Did the of water freeze in both containers at the same time? In which container did the water freeze first? What did the addition of salt do to the freezing point of water? Fresh water freezes at 32°F (0°C). What was the temperature of the salt water when it began to freeze? How does this activity explain why people put salt on icy roads and sidewalks?