SECTION #1
A chemical reaction is the process by which 1 or more substances combine to form 1 or more new substances with different properties. Clues that a reaction has taken place include the formation of a gas, a solid or a liquid, a color change, or an energy change.
A chemical equation describes what happens during a chemical reaction using symbols, formulas and coefficients. Symbols represent atoms/elements, formulas represent compounds/molecules. Equations represent what happens during the chemical changes that take place in a chemical reaction. A balanced equation uses coefficients to keep the Law of conservation of Mass true. This law states that in a chemical reaction, mass is neither created or destroyed.
There are 4 basic types of chemical reactions:
1) Composition or Synthesis - Reactants form a single product.
2) Decomposition or Analysis - A single compound is broken down into its
parts.
3) Single Replacement - A more reactive element replaces a lesser one in a
compound.
4) Double Replacement - Ions in 2 compounds switch places.
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SECTION #2
Parts of a Chemical Equation.
The left side of an equation are the Reactants, the right side are the Products. The equation is divided into the 2 sides by the Will Produce arrow. The Coefficient, multiplies everything after it until you reach a plus sign or an arrow. The Subscript, tells you how many atoms there are of whatever is directly in front of it.
Helpers go on top of the will produce arrow. A 'triangle' represents heat, a lower case 'e' represents electricity.
SECTION #3
Writing Chemical Equations.
When writing chemical equations use the 'A/B Patterns'.
1) Composition - A + B -----> AB
2) Decomposition - AB -----> A + B
3) Single Replacement - A + BC -----> AC + B
4) Double Replacement - AB + CD -----> AD + CB
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SECTION #4
Balancing Chemical Equations.
When balancing equations, the total number of atoms for each element on the left side of the equation, must equal the total number of atoms for each element on the right side of the equation.
Steps for Balancing Equations.
1) Write the equation on a single line.
2) Starting with the first element, count the number of atoms. Then
compare it to the number of atoms for that same element on the right side of the
equation. If they are equal, you do not have to do anything and you can
move on to the next element.
3) If they are unequal, you must use a coefficient greater than 1 to
balance them. Coefficients can only go in front of a single element or in
front of the first element in a compound. Remember, you never change the
original equation.
4) Repeat this procedure for the next element until all are balanced.
SECTION #5
Chemical energy.
All chemical reactions involve chemical energy. Energy is either released or absorbed in the overall reaction depending on how the energy of the reactants compares with the energy of the products. An Exothermic Reaction releases energy. An Endothermic Reaction absorbs energy. The minimum amount of energy needed to start a reaction is called the Activation Energy. The Law of Conservation of Energy states that in a chemical reaction, energy is neither created or destroyed, only changed. This means that the amount of energy put in will equal the amount of energy put out.
Reaction Rates.
How fast a reaction takes place is called its Reaction Rate. There are 4 basic factors that affect reaction rates.
1) Temperature - Increasing temperature increases
reaction rates.
2) Concentration - Increasing concentration increases reaction rates.
3) Surface Area - Increasing surface area increases reaction rates.
4) Presence of a Catalyst - A Catalyst is a substance that
speeds up the rate of a chemical reaction without itself becoming part of the
reaction. A catalyst that slows chemical reactions is called an inhibitor.