Use the terms in the boxes to fill in the blanks in the following paragraphs.

Atoms
Balanced
Chemical Reaction
Coefficients
Correct
Element
Equation
Formula
Mass
Mg
Numbers
Products
Reactants
Substance
Two
Yields

A ______is a well defined example of a chemical change. A chemical ______can be used to show the changes that occur in a chemical reaction. In a chemical reaction, the substance on the left side of the arrow are the starting substance. These substances are called ______. The substances on the right side of the arrow are the substances that result from the reaction. These substances are called ______. The arrow is read as either produces or ______.

According to the law of conservation of ______, atoms are neither lost nor gained during a chemical reaction. This law is illustrated when a chemical equation is ______. When this is done, there will be the same number of ______of each kind on both sides of the equation.

In a chemical equation, the numbers that are placed in front of the symbols and the formulas are called ______. They are necessary to keep the ______of atoms in balance.

There are several rules for balancing an equation. First, write the correct ______for each reactant and product. Next, choose the coefficients that make the number of atoms of each ______on each side of the equation equal. The correctly written formula should not be changed. If you change the formula of a substance, the equation is no longer ______. Changing a formula will indicate a ______different than the one intended.

To balance the equation Mg + O2 à MgO, first choose coefficients to make the number of atoms of each element on each side of the equation equal. You would need to place a coefficient of ______in front of the product MgO. You would also need to place a coefficient of two in front of the reactant ______.

Use the equations to answer the questions.

Zn + S à ZnS

1.  What are the reactant(s) in this chemical equation? ______

2.  What are the product(s) in this chemical equation? ______

3.  According to the law of conservation of mass, if the total mass of the product in this chemical reaction is 14 grams, what must be the combined masses of the reactants be? ______

2H2 + O2 à 2H2O

4.  What are the reactant(s) in this chemical equation? ______

5.  What are the product(s) in this chemical equation? ______

6.  What do the coefficients tell you about the ratio of reactants? ______

______

7.  How many units of product are produced? ______

Write the chemical equations for the following reactions.

8.  Two units of sodium plus one unit of chlorine gas produce two units of sodium chloride. ______

9.  One unit of methane (CH4), plus two units of oxygen (O2) produce one unit of carbon dioxide (CO2) and two units of water. ______

10.  One unit of aluminum sulfate plus three units of barium chloride yield two units of aluminum chloride plus three units of barium sulfate. ______

Label the parts of the equation using the following words: Coefficient, Reactants, Products, Subscripts, Yields.

2 K + MgBr2 à 2KBr + Mg

Classify the following chemical reactions as: Synthesis, Decomposition, Single Displacement, or Double Displacement.

______2H2 + O2 à 2H2O

______2H2O à 2H2 + O2

______Zn + H2SO4 à ZnSO4 + H2

______2CO + O2 à 2CO2

______2HgO à 2Hg + O2

______2KBr + Cl2 à 2KCl + Br2

______CaO + H2O à Ca(OH)2

______AgNO3 + NaCl à AgCl + NaNO3

______2H2O2 à 2H2O + O2

______Ca(OH)2 + H2SO4 à CaSO4 + 2H2O

True/False. Write out the word “true” or “false” for each statement.

______The new substances formed as a result of a chemical reaction are called products.

______The law of conservation of mass states that mass is neither created nor destroyed in a

chemical reaction.

______A chemical equation must be balanced in order to show that mass is conserved during

a reaction.

______Because the equation N2H4 + O2àN2+H2O has two nitrogen atoms on each side, the

equation is balanced.

______A decomposition reaction is the opposite of a synthesis reaction.

______A combustion reaction is a reaction in which a substance reacts with carbon dioxide,

often producing heat and light.

______The reaction that forms water can be classified as either a synthesis reaction or a

combustion reaction.

______The formation of chemical bonds absorbs energy.

______In exothermic reaction, the energy required to break the bonds in the reactants is

greater than the energy released as the products form.