Chemistry: Properties of Matter - Chemical vs. Physical Changes

Matter is defined as anything that has mass ($m$) and occupies volume ($V$). Its properties are categorized into physical and chemical characteristics.

Physical Properties can be observed or measured without changing the identity of the substance. Examples include density ($\rho = \frac{m}{V}$), boiling point, and solubility.

Physical Changes involve a change in the state or appearance of matter but not its chemical composition. These are often reversible, such as the phase transition of water: $H_2O(s) \rightleftharpoons H_2O(l)$.

Chemical Properties describe the ability of a substance to undergo a specific chemical change. Examples include flammability and reactivity with acids.

Chemical Changes result in the formation of one or more new substances with different properties. This involves the breaking and forming of chemical bonds, such as the combustion of methane: $CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O$.

Evidence of a chemical change includes: color change, evolution of a gas (bubbles), formation of a precipitate (solid from two liquids), and temperature change ($\Delta T$).

The Law of Conservation of Mass states that in a closed system, mass is neither created nor destroyed. Therefore, $Mass_{reactants} = Mass_{products}$.