1. Reactants: These are the substances that are present *before* a chemical change occurs. They are the ingredients that combine to form new substances.
2. Products: These are the new substances formed as a result of a chemical reaction. They are the "output" of the chemical change.
3. Formation: This word implies that a new substance is being created. For example, "the formation of water" implies that hydrogen and oxygen have combined chemically to make a new substance.
4. Decomposition: This refers to the breaking down of a substance into simpler components. Think of rotting fruit, which decomposes into simpler molecules.
5. Irreversible: Chemical changes often result in permanent changes to the original substances. This means they cannot be easily reversed by simple physical means like heating or cooling.
Important Note: While these words are often used in the context of chemical changes, they are not exclusive to them. It's important to consider the context of the situation to determine if a chemical change is actually occurring.
