* Atoms are rearranged: Chemical reactions involve the breaking and forming of chemical bonds. This means the atoms present before the reaction are still present after, but they are arranged differently.

* Energy is involved: Chemical reactions either release energy (exothermic) or require energy to occur (endothermic).

* There is a change in chemical properties: The reactants and products of a chemical reaction have different chemical properties. For example, burning wood (reactants) produces ash, carbon dioxide, and water (products), all with different properties.

* Mass is conserved: The total mass of the reactants must equal the total mass of the products. This is known as the Law of Conservation of Mass.

Important Note: While these are always true, it's also important to remember that:

* Reactions can be reversible: Some reactions can proceed in both directions, with products turning back into reactants.

* Reactions can be very fast or very slow: The rate of a reaction is influenced by factors like temperature, concentration, and the presence of a catalyst.