Chemical Reactions and Equations

• Chemical Reactions are associated with chemical change.

• Whenever a chemical change occurs chemical reaction is said to take place.

• Chemical reactions are usually irreversible and a new product is formed.

Chemical Reactions

• There are five main signs that indicate a chemical reaction has taken place.

Signs of Chemical Reactions

Change in color

Evolution of gas Production of light Formation of a solid

Absorption or release of heat

• A chemical reaction is the conversion of one substance or set of substances into another.

• Any substance that we start with is a reactant.• A new substance that forms during the reaction is

a product.

methane + oxygen carbon dioxide + water

Reactant Product

Chemical Equations

• A chemical equation is a symbolic representation of a chemical reaction.

For example:

The reactants are written on the left side, and the products are written on the right side.

An arrow shows the direction of reaction.

Chemical Equations

• The equation must represent known facts

• The equation must contain the correct formulas for the reactants and products.

• The physical state—solid(s), liquid(l), gas(g), or aqueous solution(aq)--- is shown for each reactant and product.

• The equation must be balanced.

Characteristics of Chemical Reaction

• The number of atoms of each element is the same in the products as in the reactants.

• For example:

Balanced Chemical equations

Four basic types of the chemical reactions

Types of the Chemical Reactions

• When a compound undergoes a decomposition reaction, it breaks down into the elements of which it is composed or into simpler compounds.

Decomposition Reaction

• In a combination reaction, two elements, an element and a compound, or two compounds react to produce a single compound.

Combination Reaction(Synthesis)

• In a single-displacement reaction, a free element displaces another element from a compound to produce a different compound and a different free element.

Single-displacement Reaction

• In each reaction, two compounds exchange parts to form two new compounds is called a double-displacement reaction.

Double-displacement Reaction

The End

Made by Yilin Yao(Tony)CHEM 105 11Sept 27,2016