List the three requirements for a correctly written chemical equation.

In a chemical equation, substances that start a reaction are called reactants, while those produced are known as products. To ensure accuracy, it's important to write the chemical formulas correctly. Each element is represented by its chemical symbol, and the number of atoms is indicated by subscripts. For example, in the reaction of hydrogen and oxygen to form water, hydrogen (H₂) and oxygen (O₂) are the reactants, and water (H₂O) is the product. Always double-check the chemical symbols and subscripts to make sure everything is correct. This will help in understanding what happens during the chemical reaction.

Balancing a chemical equation is crucial for representing a chemical reaction accurately. This means there should be the same number of atoms of each element on both sides of the equation. To balance the equation, you adjust the coefficients (the numbers before the chemical formulas) and not the subscripts of the formulas. For instance, the unbalanced equation for the reaction between hydrogen and oxygen might look like this: H₂ + O₂ → H₂O. However, as written, this equation isn't balanced because there are two oxygen atoms on the reactant side and only one on the product side. The balanced equation would be 2H₂ + O₂ → 2H₂O, meaning now there are four hydrogen atoms and two oxygen atoms on each side.

Indicating the states of matter in a chemical equation helps to understand the physical condition of the reactants and products. States of matter are denoted by symbols in parentheses: (s) for solids, (l) for liquids, (g) for gases, and (aq) for aqueous solutions, which means the substance is dissolved in water. For example, consider the reaction between sodium (Na) and chlorine gas (Cl₂) to form solid sodium chloride (NaCl): 2Na(s) + Cl₂(g) → 2NaCl(s). By including these symbols, it's clear that sodium and chlorine gas react to form solid sodium chloride. Always remember to check and include the physical states of all reactants and products in your chemical equations.