Chemical Reactions • All chemical reactions have two parts: • A substance that undergoes a reaction is called a reactant. In other words, reactants are the substances you start with.
Chemical Reactions • When reactants undergo a chemical change, each new substance formed is called a product. In other words, theproducts are the substances you end up with.
Chemical Reactions • The reactants turn into the products. • Reactants ® Products • In a chemical reaction, the way atoms are joined is changed. • Atoms aren’t created or destroyed.
Chemical Reactions • Chemical reactions can be described several ways. • In a sentence • Lead reacts with chlorine to form lead (II) chloride. • In a word equation • Lead + chlorine ® lead (II) chloride
Symbols Used in Equations • The arrow separates the reactants from the products • The arrow reads “reacts to form.” • The plus sign reads “and”
Symbols Used in Equations • (s) after the formula - solid • (g) after the formula - gas • (l) after the formula – liquid • (aq) after the formula – aqueous (a solid dissolved in water)
Diatomic Elements • There are 7 elements that never want to be alone. • They form diatomic molecules. • H2 , N2 , O2 , F2 , Cl2 , Br2 and I2 • The –ogens and the –ines