Name: ____________________________________ Date: ___________________ Period: _____
Chapter 7.1 Notes: Describing Reactions
A. Physical VS Chemical Properties
a. Physical Change – A change that occurs when some of the
_____________________ of a material change, but the substances in
the material remain the _________.
b. Chemical Change – A change that occurs when a substance ________
and forms one or more ______ substances.
i. Signs of a chemical change include _________ change,
_______________ change, _______ produced, ______ formed,
____________________ formed.
c. When __________ undergoes a chemical change, the
____________________ of the matter changes. When matter
undergoes a ______________ change, the composition of the
_______________ remains the same.
B. Chemical Reactions
a. A useful ________________ of a chemical reaction tells you the
______________ present ___________ and __________ the reaction.
b. Reactants – The substances that undergo __________ and are present
___________ the reaction takes place.
c. Products – The ______ substances formed as a result of that change
and are present ___________ the reaction takes place.
d. A chemical _____________ is a representation of a chemical
_______________ in which the reactants and products are expressed
as _________________.
e. Reactants  Products
Ex. 1) Burning Charcoal
Word Equation:
 Carbon + ______________ = ___________________ Dioxide
Chemical Formula:
 ____ + ______ = ______
C. Conservation of Mass
a. The Law of Conservation of Mass states that mass is neither
____________ nor ______________ in a chemical reaction.
b. Therefore the ______ of the products is always ______ to the mass of
the __________________.
c. While _____________ charcoal you actually see the ___________
burn and _________________. The same __________ of charcoal
that appears to have __________________ is actually converted into
_______ dioxide _______.
Name: ____________________________________ Date: ___________________ Period: _____
D. Balancing Equations
a. In order to show that mass is __________________ during a reaction,
a chemical equation must be __________________.
b. ______________ equations can be balanced by changing the
_______________ (the numbers that appear before symbols.)
c. When balancing a chemical equations _________ change the
____________________ in the formula.
E. Steps to Balancing a Chemical Formula
a. Step 1: Count the number of atoms of each element on each side of
the equation.
b. Step 2: change one or more coefficients until the equation is balanced.
(Only change the coefficients that need to be changed.)
Ex. 1) Write a balanced equation for the reaction between copper and
oxygen to produce copper(II) and oxide, CuO.
What do you Know?
- Reactants: _______________________
- Product: ________________________
Plan and Solve:
- Write a chemical equation with the reactants
on the left side and the product on the right
side
- _____________________________
- Change the coefficient of CuO in order to
balance the number of O atoms.
- _____________________________
- Change the coefficient of Cu.
- ___________________________________
What do you need to know?
- Balanced Equation
Answer:
Ex. 2) Balance the equation H2O2  H2O + O2
What do you Know?
What do you need to know?
- Reactants:
- Balanced Equation
_______________________
- Product: ________________________
Plan and Solve:
Answer:
- Write a chemical equation with the
reactants on the left side and the
product on the right side
- _____________________________
- Change the coefficient of H2O2 and
H2O in order to balance the number of
H and O atoms.
- _____________________________
Name: ____________________________________ Date: ___________________ Period: _____
Ex. 3) Balance the equation Mg + HCl  H2 + MgCl2
What do you Know?
What do you need to know?
- Reactants: _______________________
- Balanced Equation
- Product: ________________________
Plan and Solve:
- Write a chemical equation with the
reactants on the left side and the
product on the right side
- _____________________________
- Change the coefficient of HCl in order
to balance the number of H and Cl
atoms.
- _____________________________
Answer:
F. Counting With Moles
a. A _______ is an amount of a ______________________ that contains
approximately ________________ particles of that substance. This
number is known as ____________________ number
b. Because chemical reactions often involve large numbers of small
____________, chemists use a counting unit called the __________ to
measure amounts of a substance.
G. Molar Mass
a. Molar mass is the ______ of one _________ of a substance.
b. In the same way that a dozen _____ has a different mass than a dozen
_________, a mole of _____________ would have a different mass
than a mole of _______________.
c. The molar mass is the same as the ________ mass expressed in
__________.
d. For a _______________ you can calculate the _______ mass by
adding up the atomic masses of its component _________, and then
expressing the sum in _________.
Ex. 4) Find the molar mass of a molecule of CO2.
Name: ____________________________________ Date: ___________________ Period: _____
H. Mole-Mass Conversion
a. Once you know the molar mass of a substance, you can convert
moles of that substance into mass, or a mass of that substance into
moles.
Ex. 5) Convert 55.0 g of CO2 to moles.
What do you know?
What do you want to know?
Plan and Solve:
Use a conversion factor.
Answer:
Ex. 6) Convert 144g of H2O to moles.
What do you know?
What do you want to know?
Plan and Solve:
Use a conversion factor.
Answer: