Benchmark 4B
The Physical Setting: The Earth
Grades K-2, page 67

Water can be a liquid or a solid and can go back and forth from one form to the other. If water is turned into ice and then the ice is allowed to melt, the amount of water is the same as it was before freezing.

NSES Content Standard B 
Physical Science: Properties of objects and materials 
Grades K-4, page 127 
Materials can exist in different states--solid, liquid, and gas. Some common materials, such as water, can be changed from one state to another by heating or cooling.