Transcript (Scavenger Hunt and Intro Balancing Equations). - stroh

Catalyst – October 3+ 18, 2010
FUN GRAPH FRIDAY!
1.
2.
In what month do
you think red
light cameras
were installed in
Renton, WA?
What do you
think happened
to cause a
decrease in
citations (tickets)
issued?
Red light cameras were installed in Renton, WA and this
graph shows the number of citations issued each month.
Today’s Agenda
Catalyst
 Projects into Ms. Stroh
 Scavenger Hunt
 Notes
 College Presentation
 Exit Question
GOOD LUCK TO ACT TAKERS!

Today’s Objectives

SWBAT begin to apply law of
conservation of mass to chemical
reactions by balancing chemical
equations.
SCAVENGER
HUNT!
Whiteboard Practice

How many total atoms of each element are in these
compounds?
AlCl3: Al = ? Cl = ?
H2O: H = ? O = ?
H2O2: H = ? O = ?
KCl: K = ? Cl = ?
Be3S2: Be = ? S = ?
NH4NO3: N = ? H = ? O = ?
Balancing equations RULES!

Key Point #1: When balancing
equations, never, Never,
NEVER change subscripts, only
coefficients!
Yo, Ms. Stroh

What is a coefficient?
GOOD QUESTION!
Coefficient


A coefficient is a whole number that comes
in front of the compound formula, never in
the middle!
You multiply the coefficient to all the numbers in the
compound
2 AlCl3
Do you get it?

3 AlCl3
How
many atoms of each element do
they have?
3 Aluminum atoms
9 Chlorine atoms
How many of each atom do we have
now?
7 AlCl3
4 H2O
6 H2O2
5 KCl
2 Be3S2
4 (NH4)NO3
Why is the top equation wrong?
You figure it out (5 min)

We never want to leave an equation written like
this…
H2 +

O2  H2O
We want to have it like this…
2
H2 + O2  2 H2O
WHY???
L-C-M!!!

Key Point #2: Chemical reactions
MUST follow the Law of
Conservation of Matter.
What is the LCM?
 Matter cannot be created or destroyed.
 If 3 carbons are in the reactants of a reaction,
then there darn well better be 3 carbons in the
products of a reaction.
Balancing Chemical Reactions
H2 + O2  H2O
__H__
__O__
Write down elements.
Balancing Chemical Reactions
H2 + O2  H2O
__H__
__O__
How many are there?
Balancing Chemical Reactions
H2 + O2  H2O
_2_H_2_
__O__
How many are there?
Balancing Chemical Reactions
H2 + O2  H2O
_2_H_2_
_2_O_1_
How many are there?
Balancing Chemical Reactions
H2 + O2  H2O
_2_H_2_
_2_O_1_
Get number equal!
Balancing Chemical Reactions
Try These:
N2 + H2  NH3
P4O10 + H2O  H3PO4
Ca3P2 + H2O 
Ca(OH)2 + PH3
Balancing Chemical Reactions
Try These:
N2 + 3H2  2NH3
P4O10 + H2O  H3PO4
Ca3P2 + H2O 
Ca(OH)2 + PH3
Balancing Chemical Reactions
Try These:
N2 + 3H2  2NH3
P4O10 + 6H2O  4H3PO4
Ca3P2 + H2O 
Ca(OH)2 + PH3
Balancing Chemical Reactions
Try These:
N2 + 3H2  2NH3
P4O10 + 6H2O  4H3PO4
Ca3P2 + 6H2O 
3Ca(OH)2 + 2PH3
COLLEGE PRESENTATION???
Exit Question

1.
2.
Balance the following equations:
__KClO3 ---> __KCl + __O2
__S + __O2 ---> __SO3
Leave Notes in Folder Please!
GOOD LUCK ACT TEST TAKERS!!