A decomposition reaction is a reaction in which a compound breaks down into two or more simpler substances. The general form of a decomposition reaction is:.
Most decomposition reactions require an input of energy in the form of heat, light, or electricity. Binary compounds are compounds composed of just two elements. The simplest kind of decomposition reaction is when a binary compound decomposes into its elements.
Mercury II oxide, a red solid, decomposes when heated to produce mercury and oxygen gas. A reaction is also considered to be a decomposition reaction even when one or more of the products are still compounds.
A metal carbonate decomposes into a metal oxide and carbon dioxide gas. For example, calcium carbonate decomposes into calcium oxide and carbon dioxide:. This chemical joining is called bonding. There are many types of chemical reactions that result in chemical compounds, some of these are described in Table 1. In a chemical reaction , one or more substances undergoes a chemical change to produce a different substance or substances.
The original substances are the reactants. The new substance that results from the chemical reaction is the product. A chemical reaction is generally written in this format:. The arrow indicates that a chemical reaction has occurred.
An example of a chemical reaction is the neutralizing of stomach acid with an antacid. The chemical formula of an antacid is Ca OH 2.
Stomach acid is hydrochloric acid HCl. When these two reactants combine, they react to yield calcium chloride CaCl 2 and water H 2 O. The chemical reaction is written in this format:. This reaction reads: calcium hydroxide plus hydrochloric acid yields calcium chloride plus water. Examples of chemical reactions are given in Table 1. A reactant made of carbon and hydrogen a hydrocarbon reacts with oxygen to form carbon dioxide and water. The subscripts i and j refer to the number of C and H atoms, which are different in different hydrocarbons.
Compounds can be decomposed into simpler compounds or their elemental components by breaking bonds. Some compounds are decomposed by heating or by exposure to sunlight. For example, calcium carbonate lime stone decomposes into calcium oxide quick lime and carbon dioxide when heated.
Light decomposes hydrogen peroxide into water and oxygen Fig. Because water is an extraordinarily stable compound it does not decompose easily. The process of electrolysis uses electricity to break bonds, causing decomposition of matter. Electricity is the flow of electrons, the negatively charged particles in atoms.
In electrolysis, a chemical change is caused by electricity flowing through a chemical compound. Explore the composition of water using electrolysis. For an electrical current to flow, a circuit has to be complete.
A circuit can consist of a battery and two wires connected to electrodes that go into a solution. A Hoffman apparatus is used for the electrolysis of water. It is a glass U-tube that is filled by a thistle tube Fig. Water is still a compound, but one which cannot be broken down into hydrogen and oxygen by heating. Instead, the passage of an electrical current through water will produce hydrogen and oxygen gases.
The properties of compounds are generally very different than the properties of the elements from which the compound is formed. Sodium is an extremely reactive soft metal that cannot be exposed to air or water. Chlorine is a deadly gas. The compound sodium chloride is a white solid which is essential for all living things Figure below. A Sodium is so reactive that it must be stored under oil. B Chlorine is a poisonous yellow-green gas. C Salt crystals, a compound of sodium and chlorine.
Watch the video at the link below to answer the following questions:. Skip to main content. Matter and Change. Search for:. State basic properties of an element. Give examples of elements and their uses. Who is Sherlock Holmes? Figure 2. Summary An element is the simplest form of matter that has a unique set of properties.
One element cannot be chemically converted to another element. When was it discovered? Who discovered it? What is one use for this element? Review Questions What is an element?
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