Those occurring in your eyes and brain, for example, allow you to see these words and think about them. Even as you sit reading this chapter, chemical changes are occurring in your body. Some chemical changes are simple others are complex. To an experienced eye, these visual changes indicate a chemical change, or chemical reaction. The bubbles, flame, and color change are visual evidence that something is happening.
You heat sugar in a pan and it turns brown. You strike a match and use the flame to light a candle. YOU POUR VINEGAR INTO a glass of water containing baking soda and bubbles form. The reaction stops, leaving some excess starting material. We recognize that one reactant may be used up before others in a chemical reaction. We use the quantitative information inherent in chemical formulas and equations together with the mole concept to predict the amounts of substances consumed or produced in chemical reactions. We apply the mole concept to determine chemical formulas from the masses of each element in a given quantity of a compound.ģ.6 QUANTITATIVE INFORMATION FROM BALANCED EQUATIONS We use chemical formulas to relate the masses of substances to the numbers of atoms, molecules, or ions contained in the substances, a relationship that leads to the crucially important concept of the mole, defined as 6.022 × 10 23 objects (atoms, molecules, ions, etc.). We see how to obtain quantitative information from chemical formulas by using formula weights. We then examine some simple chemical reactions: combination reactions, decomposition reactions, and combustion reactions. We begin by considering how we can use chemical formulas to write equations representing chemical reactions.ģ.2 SOME SIMPLE PATTERNS OF CHEMICAL REACTIVITY Combustion reactions were among the first systematically studied chemical reactions. The heat and flame are visible evidence of a chemical reaction.
CHEMISTRY THE CENTRAL SCIENCE 3 STOICHIOMETRY: CALCULATIONS WITH CHEMICAL FORMULAS AND EQUATIONSĪ BURNING MATCH.
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