Kindergarten students may be amazed to discover that an ice cube will melt quite quickly in a classroom. Show an ice cube to the class and ask them what they think will happen to it if you leave it in a bowl. Ask your students how long they think the ice will take to melt. Start a stopwatch and time the melting process as your students watch. After the ice cube is liquid, stop the timer. Ask your students why an ice cube melts.
Once students understand the concept of melting, you can take the lesson further. Ask your kindergartners where they see ice and water in their everyday lives. Ask them why the ice on a skating rink does not turn to water. Encourage your students to come up with ways to make an ice cube melt more slowly or more quickly. Try giving each student an ice cube and a bowl and have them experiment with melting times. Students might try putting the bowl in a cooler place in the room or covering it with a book.
Kindergarten students should be able to identify the major practical differences between liquids and solids. Put a glass of water at the front of the classroom next to a glass of ice cubes. Ask students to think about the differences between ice and water, and which is better for drinking. Ask them why this is true. Have your students draw both cups on a sheet of paper, writing "liquid" under the water and "solid" under the ice.
Kindergartners should know that freezing water produces ice cubes. If you have a freezer available in or near your classroom, make ice cubes as a class project. Ask your students why water freezes when it is cold, and how long they think it will take for a tray of ice cubes to freeze. Put an ice cube tray filled with water in the freezer and have students check it every 20 or 30 minutes. Have them report to the class on the state of the ice cubes.