Some examples of physical changes that commonly occur in everyday life include sugar dissolving in coffee or milk, water boiling, water freezing, ice melting and the chopping of vegetables. Physical changes do not alter the fundamental identity of a substance.
The smallest structural unit of matter is known as an atom. In the early 1800s, the English chemist John Dalton formulated the modern atomic theory, which states that a chemical element is composed of the same type of atom that retains all the chemical properties of the element. Dalton further claimed that atoms combine into molecules and that molecules form into compounds.
All matter may undergo two types of changes: physical change or chemical change. A physical change is characterized by a change in size, texture, phase or shape of matter. A chemical change is associated with the breakdown or formation of chemical bonds that hold atoms or molecules together. A chemical change leads to the creation of a new product, while a physical change, often short-term and reversible, does not generate a new product.
Water is one of the most commonly occurring molecules in nature. The transformations that water undergo from one state of matter into another are examples of physical changes. Dissolving salt into water is also a type of physical change. The solid crystals of this compound can be recovered by evaporating the liquid component.