Evaluate Chemical Reactions
Uploaded by Brainy81 on Oct 20, 2023
INQUIRY LAB – BACKGROUND
Evaluate Chemical Reactions
Concepts
Chemical reactions
Law of Conservation of Mass
Balancing equations
Background
Chemical reactions involve a form of chemical change in which matter combines or breaks apart to produce new kinds of matter with different properties. Evidence for a chemical change may involve the release of a gas, a color change, the formation of a precipitate, or changes in heat or light. Any chemical change involves the reorganization of the atoms in one or more substances. For example, when carbon (C) combines with oxygen gas (O2) in the air and burns, carbon dioxide gas (CO2) is formed. This process is represented by a chemical equation, a symbolic expression used in chemistry to represent a chemical reaction. The reactants (carbon and oxygen) are written on the left side of the equation, and the products (carbon dioxide) are written on the right side of the equation. A plus sign (+) is used between two substances to indicate reactants combined or products formed. An arrow represents the direction of the reaction and is read as “yields” or “produces.”
C(s) + O2(g) → CO2(g)
Reactants Products
The chemical equation for a reaction provides two important types of information: the nature of the reactants and products and the relative numbers of each. The equation often also gives the physical states of the reactants and the products using state symbols, the symbols in parentheses written after the chemical formulas. Solids are represented with (s), liquids with (l), gases with (g), and aqueous solutions with (aq) to indicate that the substance is dissolved in water.
The basic types of chemical reactions can be broken down into five general categories: synthesis, decomposition, single replacement, double replacement, and combustion. In a synthesis reaction, two or more substances react to form a single product (e.g., X + Y → Z). In a decomposition reaction, a single reactant decomposes or breaks down into two or more products (e.g., A → B + C). In a single replacement reaction, one element replaces another in a compound such that an element combines with a compound to produce an element plus a compound (e.g., X + YZ → XY + Z). In a double replacement reaction, two compounds react to produce two different compounds (e.g., AB + CD → AD + CB). Finally, in a combustion reaction, one reactant (a fuel) combines with oxygen to produce...