A CHEMICAL REACTION TAKES PLACE whenever bonds between atoms are broken or made. In each case atoms or groups of atoms are rearranged, making new substances (products) from the original ones (reactants). Reactions happen naturally, or can be made to happen; they may take years or only a instant. Some of the main types are shown here. A reactions usually involves a change in energy. In a burning reaction, for example, the making of new bonds between atom releases energy heat and light. This type of reaction, in which heat is given off, is an exothermic reaction. Many reactions, like burning are irreversible, but in some cases the reactions are reversible (reaction in either directions). Reactions can be used to form solids from solutions; in a double decomposition reaction two compounds in solution break down and re-form into two new substance,often creating a precipitate (insoluble solid); in displacement an element (eg.copper) displace another element (eg. silver) from a solution. The rate (speed) of a reaction is determined by the shape of the reactants. To describe and keep track of reactions, internationally recognized chemical symbols and equations are used. Reactions are also used in laboratory to identify matter. An experiment with candle wax, for example demonstrates that it contains carbon and hydrogen.
Sunday, 9 February 2014
CHEMICAL REACTIONS
A CHEMICAL REACTION TAKES PLACE whenever bonds between atoms are broken or made. In each case atoms or groups of atoms are rearranged, making new substances (products) from the original ones (reactants). Reactions happen naturally, or can be made to happen; they may take years or only a instant. Some of the main types are shown here. A reactions usually involves a change in energy. In a burning reaction, for example, the making of new bonds between atom releases energy heat and light. This type of reaction, in which heat is given off, is an exothermic reaction. Many reactions, like burning are irreversible, but in some cases the reactions are reversible (reaction in either directions). Reactions can be used to form solids from solutions; in a double decomposition reaction two compounds in solution break down and re-form into two new substance,often creating a precipitate (insoluble solid); in displacement an element (eg.copper) displace another element (eg. silver) from a solution. The rate (speed) of a reaction is determined by the shape of the reactants. To describe and keep track of reactions, internationally recognized chemical symbols and equations are used. Reactions are also used in laboratory to identify matter. An experiment with candle wax, for example demonstrates that it contains carbon and hydrogen.
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