[化学] Reaction Types

Now that you are familiar with atoms and molecules and how they makeup the solids, liquids, and gases we see around us, let’s discuss whathappens when two molecules meet: namely, chemical reactions. A chemical reactionis defined as a process by which one or more substances are changedinto one or more new substances. Chemical reactions are usuallyportrayed in this way:

reactantproduct

    Theisread as “yields” or “produces.” You will often see the states of matterin parentheses as subscripts after the chemical formulas of thereactants and products. The symbols for the states of matter and someother chemical reaction symbols you should be familiar with are givenin the table below.

Symbol	Meaning
	“Yields” or “produces”
+	“Reacts with” or “and”
(g)	Gaseous state
(l )	Liquid state
(s)	Solid state
(aq)	Aqueous state (dissolved in water)
number subscript	Represents the number of atoms of the element it’s to the right of
number coefficient	How many molecules or moles of the substance are reacting
	A substance named above the arrow represents a catalyst in the reaction
	A gas is produced
	A precipitate is formed
kJ or J	Energy term (kilojoules or joules)
	Reversible equation; equilibrium
	A delta above the reaction arrow indicates that heat is added to the reaction