Example: carbon dioxide = CO2 dinitrogen monoxide = N2O
Forming New Substances Writing Formulas for Ionic Compounds
If the name contains a metal and nonmetal… the compound is probably ionic.
Forming New Substances Here’s how… Make sure the overall charge is zero. The formula may need subscripts to cause the charges of the ions to cancel out. (Remember… the charge of many ions can be determined by looking at the periodic table.) Example: Mg is in column 2, it has a +2 charge.
Types of Chemical Reactions Types of Chemical Reactions Synthesis Reactions Decomposition Reactions Single-Replacement Reactions Double-Replacement Reactions
Types of Chemical Reactions What happens when something decomposes? What happens when something synthesizes?
Types of Chemical Reactions Synthesis Reaction def: a reaction in which two or more substances combine to form a single compound. Example: A + B AB 2Na + Cl2 2NaCl
Types of Chemical Reactions Decomposition Reaction def: a reaction in which a single compound breaks down to form two or more simpler substances. Example: AB A + B H2CO3 H2O + CO2
Types of Chemical Reactions Single-Replacement Reaction def: a reaction in which an element takes the place of another element that is part of a compound. Note: the products are a new compound and a different element. Example: A + BC AC + B Zn + 2HCL ZnCl2 + H2
Types of Chemical Reactions Double Replacement Reaction def: a reaction in which ions in two compounds switch places. One of the products of this reaction is often a gas or a precipitate. Example: AB + CD AD + CB NaCl + AgFNaF + AgCl
Types of Chemical Reactions Review Questions Page 360 # 1 & 2
The energy that is released in an exothermic reaction was originally stored in the reactants.
The energy absorbed in an endothermic reaction is used to fuel the reaction and ends up in the products.
Energy & Rates of Chemical Reactions
All substances need energy to start a reaction.
Example: a match contains all the reactants needed to burn, but it will not burn until energy is added. This energy comes from the friction of striking it. Activation energy def: the minimum amount of energy needed for substances to react.