which of the following describes a chemical change

What are the nuts of chemical reactions?

What happens to chemical bonds when a chemical reaction takes place?

How are chemical reactions classified?

chemical reaction, a procedure in which 1 or more substances, the reactants, are converted to ane 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 an integral part of engineering, of civilization, and indeed of life itself. Called-for fuels, smelting iron, making glass and pottery, brewing beer, and making vino and cheese are among many examples of activities incorporating chemic reactions that take been known and used for thousands of years. Chemical reactions abound in the geology of World, in the temper and oceans, and in a vast array of complicated processes that occur in all living systems.

Chemical reactions must be distinguished from concrete changes. Physical changes include changes of country, such every bit ice melting to water and water evaporating to vapour. If a physical change occurs, the concrete properties of a substance volition alter, simply its chemical identity will remain the same. No thing what its concrete country, h2o (H₂O) is the aforementioned compound, with each molecule composed of two atoms of hydrogen and i atom of oxygen. Withal, if h2o, as ice, liquid, or vapour, encounters sodium metal (Na), the atoms will exist redistributed to give the new substances molecular hydrogen (H₂) and sodium hydroxide (NaOH). Past this, nosotros know that a chemic change or reaction has occurred.

melting ice
Melting ice, Lower Purgatory Falls, on a tributary of the Souhegan River between Mont Vernon and Lyndeborough, New Hampshire. Water ice melting is a physical modify and not a chemical reaction.
Wayne Dionne/© New Hampshire Division of Travel and Tourism Development

Historical overview

The concept of a chemical reaction dates dorsum about 250 years. It had its origins in early experiments that classified substances as elements and compounds and in theories that explained these processes. Development of the concept of a chemical reaction had a primary office in defining the science of chemistry equally information technology is known today.

The commencement substantive studies in this expanse were on gases. The identification of oxygen in the 18th century past Swedish chemist Carl Wilhelm Scheele and English chaplain Joseph Priestley had particular significance. The influence of French chemist Antoine-Laurent Lavoisier was especially notable, in that his insights confirmed the importance of quantitative measurements of chemical processes. In his book Traité élémentaire de chimie (1789; Elementary Treatise on Chemical science), Lavoisier identified 33 "elements"—substances not broken downwardly into simpler entities. Among his many discoveries, Lavoisier accurately measured the weight gained when elements were oxidized, and he ascribed the outcome to the combining of the chemical element with oxygen. The concept of chemical reactions involving the combination of elements clearly emerged from his writing, and his approach led others to pursue experimental chemistry as a quantitative science.

The other occurrence of historical significance concerning chemical reactions was the development of atomic theory. For this, much credit goes to English chemist John Dalton, who postulated his atomic theory early in the 19th century. Dalton maintained that matter is composed of small, indivisible particles, that the particles, or atoms, of each chemical element were unique, and that chemical reactions were involved in rearranging atoms to form new substances. This view of chemical reactions accurately defines the electric current subject. Dalton'southward theory provided a basis for understanding the results of earlier experimentalists, including the law of conservation of matter (matter is neither created nor destroyed) and the law of constant composition (all samples of a substance take identical elemental compositions).

Thus, experiment and theory, the two cornerstones of chemical science in the modernistic world, together defined the concept of chemical reactions. Today experimental chemistry provides innumerable examples, and theoretical chemical science allows an agreement of their meaning.

Bones concepts of chemical reactions

Synthesis

When making a new substance from other substances, chemists say either that they carry out a synthesis or that they synthesize the new fabric. Reactants are converted to products, and the process is symbolized past a chemical equation. For example, iron (Fe) and sulfur (S) combine to form atomic number 26 sulfide (FeS). Fe(south) + S(s) → FeS(due south) The plus sign indicates that iron reacts with sulfur. The arrow signifies that the reaction "forms" or "yields" iron sulfide, the product. The state of matter of reactants and products is designated with the symbols (s) for solids, (fifty) for liquids, and (one thousand) for gases.