What is the result of a chemical change?

The formation of a new substance is a key characteristic of a chemical change. During a chemical change, reactants undergo a transformation at the molecular level, resulting in products that have different properties from the original substances. This often involves breaking and forming chemical bonds, leading to the creation of substances that are chemically distinct.

For instance, when iron rusts, oxygen reacts with iron to form iron oxide, which is not the same as elemental iron or oxygen. This new substance has different physical and chemical properties, such as color, density, and reactivity. This definitive change in the identity of substances is what sets chemical changes apart from physical changes, which may alter the state or appearance of a substance but do not change its chemical composition.

The other options provided do not accurately reflect the nature of a chemical change. The separation of mixtures typically refers to physical processes such as filtration or distillation, while the alteration of physical properties and evaporation of liquids are also related to physical changes rather than chemical transformations.