How are chemical changes different from physical changes? (Lesson 3)
Chemical changes are different from physical changes in several ways.
1. Formation of new substances: Chemical changes involve the formation of new substances with different chemical properties compared to the original substances. In a chemical change, the atoms rearrange to form new chemical bonds, leading to the creation of a new substance. In contrast, physical changes do not result in the formation of new substances. The composition and chemical properties of the original substances remain the same in physical changes.
2. Permanence of change: Chemical changes are typically irreversible, meaning that the new substances formed cannot be easily converted back into the original substances. Once a chemical change occurs, it is challenging to reverse it. On the other hand, physical changes are usually reversible, and the original substances can be obtained by simply reversing the physical conditions or processes involved.
3. Energy changes: Chemical changes often involve energy changes, such as the release or absorption of heat, light, or sound. These energy changes are often indicative of chemical reactions taking place. In physical changes, there may be energy changes too, but they are usually not as significant as in chemical changes. For example, a physical change like changing the state of matter (such as melting or boiling) results in energy changes, but these changes do not indicate a chemical reaction.
4. Nature of change: Chemical changes involve a transformation at the molecular level, where the arrangement of atoms in a substance is altered to form new molecules and compounds. In physical changes, the molecules and atoms do not change their composition; only their physical state or arrangement may be affected.
In summary, chemical changes involve the formation of new substances with different chemical properties, are usually irreversible, involve significant energy changes, and occur at the molecular level. In contrast, physical changes do not involve the formation of new substances, are often reversible, may involve minor energy changes, and do not change the composition of substances at the molecular level.