When working with ice, children should understand that ice is the solid form of water. Young children can explore this by playing with ice cubes and noticing that they turn into water as they melt. Show the children that the gaseous form of ice and water is steam by boiling water in a kettle, taking care to keep the youngsters away from the steam to avoid burns. Have the children draw on construction paper the different forms that water takes, and display their art in the classroom.
Most children already know that ice floats in water. Demonstrate this with a pitcher of ice water. Show them that ice also floats in orange juice, soft drinks and milk. Older children may know that oil floats in water as well, and you can easily demonstrate this with a bottle filled with half water and half oil. Ask them whether they think that ice will sink or float in oil, then perform the experiment after hearing their hypotheses. Since ice is less dense than oil, it will float.
Salt has an interesting effect on ice. First, it lowers the freezing point to below 32 degrees. Demonstrate this by filling some wells in an ice cube tray with tap water, and some wells with salt water. Make the salt water by mixing a teaspoon of salt into a glass of tap water. Place the tray in the freezer. You and the children then check the ice cubes' progress periodically. After this project, you can lead your classroom discussion to the topic of icebergs, which are frozen salt water.
Another effect that salt has on ice is that it causes ice to quickly melt and freeze again. Float an ice cube in a glass of water and challenge your students to pick up the cube with a piece of string without getting their hands wet. They will most likely try to loop the string under the cube, which won't work. The answer to the challenge is to lay the string across the ice cube and to sprinkle it with salt. The salt will melt the ice slightly, then the ice will refreeze over the string, getting stuck on the string. This project can lead to a discussion about why trucks spread salt on the roads after a snow or ice storm.