Esters are formed through an esterification reaction when a carboxylic acid reacts with an alcohol in the presence of a concentrated sulfuric acid catalyst. Esters have various physical properties including being colorless liquids at room temperature with sweet, pleasant smells and low boiling points and densities. They are found naturally in many plants and fruits where they contribute to smells and flavors. Esters have several applications including use as food flavorings, in cosmetics, fragrances, and medicines.