Chemical Reactions By: Stephayy81

Chemical Reaction Basics Reactant: The substance that is participating in the reaction. Product: A substance that is formed as a result of the chemical reaction. What's Happening? Every type of chemical reaction differs, however, in simplest terms, bonds are broken and formed by the interactions of electrons.

Signs of a Chemical Reaction A formation of a gas is one way to tell that a chemical reaction has taken place. A formation of a solid is another way to tell that a chemical reaction has taken place

Signs of a Chemical Reaction If a chemical has changed color or has produced energy, it’s a sign that a chemical reaction has taken place

Signs of a Chemical Reaction One last way to tell if a chemical reaction has taken place is a change in temperature.

Law of Conservation of Mass The law of conservation of mass, states that in a chemical reaction, mass cannot be destroyed nor created. So the mass of a products always equal to the mass of the reactants.

Energy and Chemical Reactions Chemical potential energy is the energy stored in the bonds of atoms or molecules. For example, when fuel is burning, the energy is transformed into heat.

Activation Energy Activation energy is energy that must be overcome in order for a chemical reaction to occur. For a reaction to occur between two colliding molecules, the molecules must collide in the correct arrangement and must possess a minimum amount of energy.

Exothermic Reactions An exothermic reaction is a chemical reaction that releases heat. For example, the burning of wood is an example of an exothermic reaction.

Endothermic Reactions An endothermic reaction absorbs as much energy as possible. An example of an endothermic reaction is melting ice.

Types of Chemical Reactions In a synthesis reaction, two or more simple substance combine to form a more complex substance. Example: Hydrogen gas combined with Oxygen gas produces water. 2 H 2 + O2  2 H 2 O How to tell: If two or more reactants yield one substance.

Decomposition Reaction In a decomposition reaction, a more complex substance breaks down into its more simple parts. How to tell: One reactant yields two or more products. Example: Water can be broken down into hydrogen gas and oxygen gas. 2 H 2 0  2 H 2 + O

Combustion Reaction A combustion reaction is when Oxygen is a reactant. How to tell: It is an exothermic reaction, and produces heat. Example: CH 4 + 2O 2  CO 2 + 2H

Single Replacement In a single replacement, one element trades places with another element in a compound. How to tell: You’ll see two reactants yield two products. Example: Mg + 2 HCI  MgCI 2 + H 2

Double Replacement In a double replacement reaction, anions and cations of two different molecules switch places, producing two different compounds. How to tell: You’ll see two reactants yield two products. Example: Pb(NO3)2 + 2 KI ---> PbI2 + 2 KNO3