The total amount of matter is conserved (stays the same) when it undergoes a physical change such as when an object is broken into tiny pieces, when a solid is dissolved in a liquid, or when matter changes state (solid, liquid, gas).
Matter: Properties and Change
In prior grades students learned to identify different physical properties of matter and to realize that an object may be made from several different types of materials. In grades 4-5 students learn that a given substance may exist in different states-solid, liquid, and gas-and that many substances can be changed from one state to another. This understanding of matter lays the foundation for later explanations of matter in terms of atomic theory.