Classifying Chemical Reactions

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Synthesis Reaction Noun

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[sin-thuh-sis ree-ak-shun]

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Synthesis Reaction

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A chemical reaction in which two or more substances react to produce a single, more complex product.

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Example: Two simple hydrogen molecules and one oxygen molecule combine (synthesize) to form two more complex water molecules.

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Combustion Reaction Noun

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[kum-buhs-chun ree-ak-shun]

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Combustion Reaction

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A chemical reaction where a substance combines with an oxidant, usually oxygen, and releases energy as heat and light.

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Example: This diagram shows the inputs and outputs of a combustion reaction: a hydrocarbon (like coal) plus oxygen react to produce carbon dioxide, water, heat, and light.

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Decomposition Reaction Noun

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[dee-kom-puh-zish-un ree-ak-shun]

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Decomposition Reaction

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A chemical reaction in which a single compound breaks down into two or more simpler elements or compounds.

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Example: The image shows a large starch molecule breaking down into many smaller glucose molecules, illustrating how a single, complex substance decomposes into simpler ones.

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Replacement Reaction Noun

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[ri-pleys-muhnt ree-ak-shun]

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Replacement Reaction

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A reaction, also known as a displacement reaction, that involves the replacement of an element in a compound.

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Example: This diagram shows a single replacement reaction where element C displaces element B from the compound AB, forming a new compound BC and leaving element A by itself.

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Single-Replacement Reaction Noun

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[sing-guhl ri-pleys-muhnt ree-ak-shun]

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Single-Replacement Reaction

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A reaction in which the atoms of one element replace the atoms of another element within a compound.

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Example: This diagram shows a single element (A) taking the place of another element (B) in a compound (BC), resulting in a new compound (AC).

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Double-Replacement Reaction Noun

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[duhb-uhl ri-pleys-muhnt ree-ak-shun]

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Double-Replacement Reaction

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A reaction involving an exchange of ions between two compounds, resulting in the formation of two new compounds.

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Example: This image shows a double-replacement reaction where two compounds, silver nitrate (AgNO3) and sodium chloride (NaCl), swap partners to form two new compounds.

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Hydrocarbon Noun

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[hahy-droh-kahr-buhn]

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Hydrocarbon

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An organic compound that contains only carbon and hydrogen atoms, often burning in oxygen to produce energy.

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Example: This image shows a model of methane (CH₄), the simplest hydrocarbon. Hydrocarbons are chemical compounds made only of hydrogen (blue) and carbon (grey) atoms.

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Reactivity Noun

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[ree-ak-tiv-i-tee]

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Reactivity

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The ability or tendency of a substance to undergo a chemical reaction with another substance.

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Example: This image shows iron powder reacting with hydrochloric acid to produce gas bubbles, demonstrating that iron is a reactive metal.

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Activity Series Noun

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[ak-tiv-i-tee seer-eez]

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Activity Series

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A list of elements ordered by chemical reactivity, used to predict the outcomes of single-replacement reactions.

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Example: This chart, an activity series, ranks elements by how reactive they are. Elements at the top, like potassium, are more reactive than elements at the bottom.

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Precipitate Noun

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[pri-sip-i-teyt]

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Precipitate

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An insoluble solid that is formed from a liquid solution during a chemical reaction.

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Example: When some solutions undergo a chemical reaction, a solid called a precipitate can form and settle out of the liquid, as shown in the test tube.