WARM – UP:




Update your Table of Contents
Write your homework – leave it to be stamped
Get a marker from the blue basket and get
ready to grade your test also!
Get your Adopt-An-Element Baby Book out,
but DO NOT turn it in yet…we are going to
grade it!
Date
Session
#
10/16
10/17
19
Activity
Law of Conservation of Mass Notes & Lab
Page
#
32
Physical & Chemical changes can
change matter, BUT…THE REAL
QUESTION IS:
During those changes, is any
matter created or destroyed?
Law of Conservation of Mass/Matter
Law of Conservation of Mass/MatterMatter cannot be created or destroyed, it
can only change form.
So where does the wood go?
Na
F
NaF
IN OTHER WORDS…
What goes in, must come out!
Open System/Reaction

The container in which the reaction is
performed is open - matter may escape
Closed System/Reaction

The container in which the reaction is
being performed is closed so all of the
matter will be contained – nothing escapes
Dry Ice Demo
 Watch
the dry ice demo
 Write ANY observations!
 Explain how this demonstrates
The Law of Conservation of Mass!
Dry Ice Demo
Dry Ice = Solid Carbon Dioxide
 Freezing Point of Carbon
-108.4oF or -78oC
 Boiling Point of
-76oF or -57oC
 Formula:
CO2(s)
Dioxide =
Carbon Dioxide =
Is this physical or chemical?
CO2(g)
Law of Conservation of Mass (Matter) Lab
Investigation Roles





Group Leader – Reading and making sure the group is
following directions accurately and completing all parts
of the lab
Supply Manager – Gets, returns & cleans supplies
Measurement Technician – gets and returns the scale
balance and is responsible for accurate mass
measurements
Data Discussion Technician – makes sure the group
records the mass data before and after the experiment,
AND everyone has an explanation for THE TEACHER
DEMO, STUDENT LAB & COMPARE & CONTRAST
ONE LAB GUIDE WILL BE PICKED FOR THE GROUP GRADE
Law of Conservation of Mass (Matter) Lab
Investigation


Send your supply manager to get the lab kit
and your measurement technician to get the
scale balance.
Group leader, read the directions carefully each
step of the way!!
◦ WARNING: YOUR BALLOON IS ALREADY FULL
OF BAKING SODA, DO NOT TIP IT INTO THE
GRADUATED CYLINDER ACCIDENTALLY!
Law of Conservation of Mass (Matter) Lab
Investigation Clean-Up






Balloons in the garbage
Rinse graduated cylinder thoroughly
Wipe up any spills
Put all items back into your lab kit & put them
on the front counter
Put scale balance back onto the back counter
Make sure every group member has
measurements and ALL parts of the lab guide
are complete
Compare & Contrast
 Again,
the explanation should
state how BOTH experiments
demonstrated the Law of
Conservation of Mass…BUT,
what were the similarities and
differences between them?
WARM – UP:
Update your Table of Contents
 Write your homework – leave it to be
stamped
 What does the Law of Conservation of
Mass/Matter state?

Date
10/20
10/21
Session
#
20
Activity
Page
#
Balancing Act Note Guide
33
Balancing Equations Practice
34
What does the Law of
Conservation of
Mass/Matter state?
Na
F
NaF
REMEMBER: What goes in,
must come out!
Chemical Reactions
Reactants –
Elements OR
compounds
present at the
beginning of a
chemical
reaction
Product –
Compounds
formed by
a chemical
reaction
R
E
A
C
T
A
N
T
S
P
R
O
D
U
C
T
Balancing Chemical Equations

Since matter can neither be created or
destroyed, the mass/amount of
reactants must always equal the
mass/amount of products
Balancing Chemical Equations

Before (Reactants)
Na
F

After (Product)
NaF
Na = 1
Na = 1
F=1
F=1
Na
F
NaF
The arrow indicates that
a change has occurred
Chemical formulas
for elements
Chemical formula
for new compound
2H2 + O2  2H2O
Coefficient
Subscripts
(Reactants)
Subscript
Coefficient
(Products)
What is that little number?
Subscript –
◦ Shows how many atoms of an
element are in a compound.
◦ When there is NO subscript there is
only 1 atom of that element.
O2
NaCl
NH4
K5N4C2
What is that big number in front?
Coefficient –
◦ The number of molecules
(compounds) involved in a chemical
reaction
H2
O2
H2
2 H2
O2
2
H2O
So the coefficient tells you the number of
molecules, but what about each atom?
 You must multiply…it is like the
distributive property in math!
3O2
2NH4
5H2O
2Li3F2
4NaCl
2K5N4C2
Rules for Balancing Chemical Equations
1. You CANNOT change subscripts, you can
ONLY change coefficients
H2 + O2
2H2O
2. It does NOT have to look the same on both
sides, it only has to be balanced
3. You CANNOT split compounds to write in a
coefficient:
HCl
Rules to Balancing Chemical Equations
4. Only multiply through when it is a compound
because they have already bonded
2H + Cl
NO
2HCl
YES
5. If it is a capital letter, they are each a
separate element:
H, C, O
If it is a capital letter followed by a lower
case letter, it is all one element:
Cl, Li, Si
Steps for Balancing Chemical Equations


1. Divide the reactants from the products
with a line.
2. Write down the chemical symbol of each of
the elements on each side of the equation
2 H2 + O
2
2H2O
H=
H=
O=
O=
Steps to Balancing Chemical Equations


3. Using the coefficients and subscripts write
down the number of each element
4. If they are not balanced change the
coefficients using trial and error. You will have
to go back and forth between each side!
2 H2 + O
2
2H2O
H=4
H=4
O=2
O=2
Lets Practice
P + O2
P 4O6
Lets Practice
Na + O2
Na2O
Lets Practice
Al2O3
Al + O2
Lets Practice
Cl2 + KI
KCl + I2
WARM – UP:
Update your Table of Contents
 Write your homework – leave it to be
stamped
 Complete the Warm-Up side of the note
guide

Date
10/22 10/23
Session
#
21
Activity
Endothermic Reactions Vs. Exothermic
Reactions
Page
#
35
Law of Conservation of Mass (Matter)
Law of Conservation of Mass (Matter)Matter cannot be created or destroyed, it
can only change form
In other words…
What goes in, must come out!
Law of Conservation of Mass (Matter)
Analyzing Reactions


Some chemical reactions are
ENDOTHERMIC = take “in” or absorb
energy
Some chemical reactions are
EXOTHERMIC = give “out” or produce
energy
How would you tell the difference?
Endothermic Reactions



An endothermic reaction takes “in” or
absorbs energy
Causes temperature around it to cool (will
feel cold)
EXAMPLE: Photosynthesis (needs energy
from the sun)
Exothermic Reactions



An exothermic reaction gives “out” or
produces energy (heat, light or sound)
Causes temperature around it to rise
(feels warm/hot)
EXAMPLE: cellular respiration (gives
energy to your cells)
Endo & Exo Lab Investigation Roles




Group Leader – Responsible for reading and
making sure the group is following directions
accurately
Supply Manager – gets and returns supplies
and makes sure they are clean
Data Discussion Technician – makes sure the
group records all observations and has an
explanation for BOTH investigations!
Speaker – Group member that must share your
explanation/conclusion with the class.
REVIEW
BALANCING
EQUATIONS…Please
get your Rules & Steps
for balancing
equations out!
Rules for Balancing Chemical Equations
1. You CANNOT change subscripts, ONLY
coefficients
H2 + O2
2H2O
2. It does NOT have to look the same on both
sides, it only has to be balanced
3. You CANNOT split compounds to write in a
coefficient:
HCl
Rules to Balancing Chemical Equations
4. Only multiply through when it is a compound
because they have already bonded
2H + Cl
NO
2HCl
YES
5. If it is a capital letter, they are each a
separate element:
H, C, O
If it is a capital letter followed by a lower
case letter, it is all one element:
Cl, Li, Si
Steps for Balancing Chemical Equations


1. Divide the reactants from the products
with a line.
2. Write down the chemical symbol of each of
the elements on each side of the equation
2 H2 + O
2
2H2O
H=
H=
O=
O=
Steps to Balancing Chemical Equations


3. Using the coefficients and subscripts write
down the number of each element
4. If they are not balanced change the
coefficients using trial and error. You will have
to go back and forth between each side!
2 H2 + O
2
2H2O
H=4
H=4
O=2
O=2
Last Chance to Balance


Balance the 5 equations on the sheet – if you
get them correct you will be using the
Chromebooks for the remainder of class to
complete the “Study Buddy Review”
If you get them incorrect you will move up to
the front counter with me practicing how to
balance equations.
REVIEW



Play the review games listed on the sheet on top
of the Chromebook cart.
You may play with a partner if the game
requires 2 players.
If you get through all of them ONLY then can
you search for alternate CHEMISTRY RELATED
sites/games!!
EXPECTATIONS


I expect you and your partner to play
only what you are supposed to
without being disruptive in any way so
that I can focus on helping the people
who need it!!
When you are working with me you
are expected to complete the
equations!!
Equation 1 - Balance Box Answer
P + O
P4O10
Equation 2 - Balance Box Answer
Cl₂ + NaBr
NaCl +
Br₂
Equation 3 - Balance Box Answer
Cs
+
N₂
Cs3N
Equation 4 - Balance Box Answer
CuCl₂
+
H₂S
CuS + HCl
Equation 5 - Balance Box Answer
Al +
HCl
AlCl₃
+
H₂
Balancing Equations Practice
Homework

Find the Balancing Equations Practice
Homework or take another sheet – we will
work on a few together, and then you can
practice on your own.
Lets Practice: Part D - #1
Na + MgF2
NaF + Mg
Lets Practice: Part D - #2
Cl2 + KI
KCl + I2
IMPORTANT:
Cl = Chlorine
K & I are 2 separate
elements
Lets Practice: Part D - #3
HCl + NaOH
NaCl + H2O
Lets Practice: Part D - #4
Na + NaNO3
Na2O + N2
Lets Practice: Part D - #5
PbBr2 + HCl
HBr + PbCl2
REVIEW
Try
6, 7 & 8 on
your own, and
then check the
answer key
Lets Practice: Part D - #6
Na3P + CaF2
NaF + Ca3P2
Lets Practice: Part D - #7
AlBr3 + K
KBr + Al
Lets Practice: Part D - #8
CaF2 + Li2SO4
CaSO4 + LiF