Why do physical changes not produce new substances?

Physical changes do not produce new substances because they only alter the form or state of a substance, not its chemical composition.

Physical changes are transformations that do not affect the internal structure of the molecules of a substance. They are changes in the physical properties of a substance, such as its shape, size, colour, or state of matter (solid, liquid, or gas). These changes are often reversible, meaning the substance can return to its original state. For example, when water freezes into ice, it undergoes a physical change from a liquid to a solid state. However, it remains H2O, with the same chemical properties as before.

In contrast, chemical changes involve a substance reacting to form one or more new substances with different chemical properties. These changes are usually irreversible. For instance, when hydrogen reacts with oxygen to form water, new substances (water molecules) are produced, which have different properties from the original hydrogen and oxygen gases.

Physical changes do not produce new substances because they do not involve changes in the substances' molecular or ionic structures. The atoms or ions in a substance are not rearranged in a physical change, so no new substances are formed. For example, when you cut a piece of paper, you are changing its physical shape, but the paper's chemical composition remains the same.

In summary, physical changes are about altering the appearance or state of a substance without changing its chemical identity. They do not produce new substances because they do not involve any changes in the arrangement of atoms or ions in a substance.