Scope, Sequence, and Coordination

A Framework for High School Science Education

Based on the National Science Education Standards

Acids, Bases and Indicators

Oxidation/Reduction, Acid/Base, and Radical Reactions
A large number of important reactions involve the transfer of either electrons (oxidation/reduction reactions) or hydrogen ions (acid/base reactions) between reacting ions, molecules, or atoms. In other reactions, chemical bonds are broken by heat or light to form very reactive radicals with electrons ready to form new bonds. Radical reactions control many processes such as the presence of ozone and greenhouse gases in the atmosphere, burning and processing of fossil fuels, the formation of polymers, and explosions.

Further Description:

Compounds can be classified according to their chemical and physical properties. They can also be classified according to their molecular structures. Some important classifications include oxidizing and reducing agents, organic and inorganic chemicals, and acids and bases. Some processes that involve electron transfer include combustion, corrosion, electrochemistry, and production of metals from ores. Other reactions involve proton or hydrogen ion transfer.

The most common acid-base reaction consists of hydrogen ions combining with hydroxide ions to form water in a process called neutralization. Acid solutions can be differentiated from basic solutions by measuring their pH. In some chemical reactions under special circumstances, highly reactive species (radicals) are created and form intermediate species, such as in atmospheric chemistry and in chemical reactions occurring in flames. These species can be predicted from atomic and molecular structure and available energy.

Concepts Needed:

Grade 9

Oxidation, neutralization, acid, acid-base indicator, concentration

Grade 10

Reduction, corrosion, ion

Grade 11

Oxidizing agent, voltage (electrode potential), titration, end point, photochemistry, electroplating, electrolyze, electrolytic cell, reducing agent, half-reactions, ion, radical, pH, conjugate pairs

Grade 12

Ionization, radicals, radical reactions

Empirical Laws or Observed Relationships:

None suggested

Theories or Models:

Chemical bond, atomic structure, Bronsted-Lowry theory (definition) of acids and bases, Arrhenius=s theory of ionization

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Micro-Unit Description:

Acids, Bases and Indicators
Students should mix acid and base solutions back and forth to observe that one neutralizes the properties of the other. They should also observe the color changes of some common indicators and observe what occurs when an acid or base is added to a water solution.

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