Chapter Two: Types of Chemical Reactions

In different reactions atoms or ions rearrange themselves in different ways. There are three types of reactions: Synthesis (combination), Decomposition, Displacement (single or double).

Source: http://www.blurtit.com/groups/The_Amazing_World_Of_Chemistry_And_Physics

Synthesis (combination reactions)

In chemical laboratories, as well as in industry, synthesis reactions are used to produce new substances from simpler substances.A and B are elements or compounds and AB is a complex compound. This reaction gives off energy. This type of reaction is represented by the following equation:

A + B gives AB

Decomposition Reactions

The decomposition of most pure substances takes place when energy is used. This type of reactions is represented by the general equation:

AB gives A + B

Displacement Reactions
a) Single displacement reactions: The general equation for this reaction is

A + BC gives AB + C

b)Double Displacement reactions: The general equation for this type of reaction is

AB + CD gives AD + CB

Question: What do you think makes Displacement reactions exothermic?

Chapter One: Chemical Equations and Reactions (part 2)

Balancing Chemical Equations:
1- Write the Word Equation for the reaction
2-Write symbols and formulas for reactants and products
3-Count the number of atoms of each element on each side of the arrow
4-balance the equation using coefficients. There should be the same number of each atom on each side of the equation
5-Coefficients should be the smallest whole number.

Example:
Step 1: methane+oxygen yields carbon dioxide+water
step 2: CH4+O2 yields CO2+H2O
step 3: count the number of atoms of each element on each side of the arrow
step 4: CH4+2O2 yields CO2+2H2O
step 5:Check coefficients!

Question: Why do you think we need balanced equations as opposed to unbalanced equations?

Chapter One: Chemical Equations and Reactions (part 1)

Chemical reactions govern our whole lives. Without them we cannot survive. The first chapter deals with realizing the importance of chemical reactions, writing chemical equations, and balancing them.
The process by which a chemical change takes place is called a chemical reaction. New substances are formed as a result of a chemical reaction. The chemical identities of the substances entering into a reaction are not the same as those which result from it. When a chemical reaction takes place, there is always a change in the properties and in the energy content of substances involved in the chemical reaction.
A word equation represents the names of the reactants and the products.
Example: Potassium hydroxide + Iron (II) nitrate Potassium nitrate + Iron (II) hydroxide
An unbalanced chemical equation is a description of a chemical reaction using symbols and formulas for the reactants and the products.
Example: Fe(NO3)2(aq) + KOH(aq) Fe(OH)2(s) + KNO3(aq)
A chemical Equation is a shorthand expression for a chemical reaction. In addition to telling us what are the reactants and products, it tells us the relative numbers of each (coefficients).
Example: Fe(NO3)2(aq) +2 KOH(aq) Fe(OH)2(s) + 2KNO3(aq)
The four types of reactions in aqueous solutions are:
- Formation of a precipitate
- Formation of water
- Formation of gas
- Transfer of electrons

http://people.bath.ac.uk/ch3mw/

Qusetion: Come up with a reaction and write it in the three forms (word,unbalanced, and balanced).

Welcome!

Welcome to the Chemical Reactions Blog. This blog is offered to Grade 8 students at International College. We will use this blog to share information and post announcements.