Chemical Reactions and Equations

Summary:

This Chemical Reactions and Equations text explains the nature of chemical reactions, differentiates them from physical changes, and the process of balancing a chemical equation.

Chemical reactions involve transforming one or more substances (reactants) into different substances (products). These reactions are crucial to life, technology, culture, and natural processes on Earth. Unlike physical changes (like melting ice), chemical reactions involve a change in the chemical identity of substances. For example, when water (H2O) encounters sodium (Na), it results in the formation of molecular hydrogen (H2) and sodium hydroxide (NaOH), demonstrating a chemical change.

Balancing chemical equations is an essential part of understanding chemical reactions. In a balanced chemical equation, the number of atoms for each element is the same before and after the reaction. The text gives an example of a balanced equation (Zn + H2 SO4 → ZnSO4 + H2) and outlines a step-by-step method for balancing a more complex equation (Fe + H2O → Fe3O4 + H2). This process involves counting the atoms of each element, adjusting coefficients to balance elements one by one, and verifying that the equation is balanced at the end.

The physical states of reactants and products are sometimes included in a chemical equation using notations: (g) for gases, (l) for liquids, (aq) for aqueous solutions, and (s) for solids. These states and other reaction conditions like temperature, pressure, or catalyst may be added to the equation to provide more detail about the reaction.

Excerpt:

Chemical Reactions and Equations

A chemical reaction is a process in which one or more substances, the reactants, are converted to one or more different substances, the products. Substances are either chemical elements or compounds. A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products.

Chemical reactions are integral to technology, culture, and life. Burning fuels, smelting iron, making glass and pottery, brewing beer, and making wine and cheese are among many examples of activities incorporating chemical reactions that have been known and used for thousands of years.

Chemical reactions abound in the geology of Earth, the atmosphere and oceans, and a vast array of complicated processes that occur in all living systems.