Unit 6 reactions: Lesson 1: conservation and balancing equations

MONDAY 11/28: UNIT 6 INTRODUCTION: CHEMICALREACTIONS & BALANCINGEQUATIONS

▪ Phones up by the bell!
▪ Thursday 12/1- popcorn lab quiz

Friday 12/2- elearning day​

▪ Tuesday 12/6 Unit 6 Quiz 1
▪ Friday 12/9 Unit 6 test

▪ Thursday 12/15 Benchmark 2 on units 4-6

Q2 ends on 12/19​

​

ANNOUNCEMENTS/REMINDERS:

 PPT: Conservation of matter& balancing equations

 CWK- choice board on GC

AGENDA:

Bellwork:

1. Pick up unit 6 packet
2. Start pg 1 in packet

Multiple Choice

What is the left part of a chemical equation called?

2H₂ + O₂ ---> 2H₂O

• Reactants

• Yields

• Products

• Chemical equation

Multiple Choice

What is the right part of a chemical equation called?

2H₂ + O₂ ---> 2H₂O

• Reactants

• Yields

• Products

• Chemical Equation

Multiple Choice

What is the little number after an element in a chemical equation called?

Example: H₂

• Coefficient

• Atom

• Subscript

• Equation

Multiple Choice

What is the number before a chemical formula called?

Example: 2H₂ + O₂ ---> 2H₂O

• Coefficient

• Atom

• Subscript

• Equation

CHEMICAL EQUATIONS

• CHEMICAL REACTIONS ARE REPRESENTED BY A CHEMICAL

EQUATION IN WHICH THE CHEMICALS PRESENT BEFORE THE
REACTION (THE REACTANTS) ARE SHOWN TO THE LEFT OF AN
ARROW AND THE CHEMICALS FORMED BY THE REACTION (THE
PRODUCTS) ARE SHOWN TO THE RIGHT OF THE ARROW

• THE ARROW INDICATES THE DIRECTION OF THE CHANGE AND IS

READ AS "YIELDS" OR "PRODUCES"
• EX: A + B🡪 AB
•2H2 + O2🡪 2H2O

CHEMICAL EQUATIONS

• IN A CHEMICAL REACTION ATOMS ARE NEITHER

CREATED NOR DESTROYED, THEY ARE JUST
REARRANGED, MEANING A CHEMICAL
REACTION ONLY CHANGES THE WAYS IN WHICH
THEY ARE GROUPED

• MAKING SURE THAT THE NUMBER OF ATOMS OF

EACH TYPE OF ELEMENT IS THE SAME ON EACH
SIDE IS KNOWN AS BALANCING THE REACTION
(OR EQUATION)

LAW OF CONSERVATION OF

MATTER

WHY ARE CHEMICAL EQUATIONS, AND BALANCED
CHEMICAL EQUATIONS, SO IMPORTANT?
•MATTER CANNOT BE CREATED OR DESTROYED, BUT CAN
ONLY CHANGE FORMS

SO WHEN WE WRITE EQUATIONS…
•THE NUMBER OF EACH TYPE OF ATOM ON THE REACTANTS
SIDE MUST BE EQUAL TO THE NUMBER OF EACH TYPE OF
ATOMS ON THE PRODUCTS SIDE

• # OF ATOMS OF REACTANTS = # OF ATOMS OF PRODUCTS

Multiple Choice

How many Mn atoms are found in the following compound?

2MnO₄

• 1

• 2

• 4

• 8

Multiple Choice

What is the Law of Conservation of Mass?

• It states that matter cannot be created or destroyed.

• It states that energy cannot be created or destroyed.

• It states that matter can be created or destroyed.

• It states that sound can be created or destroyed.

Page 3

BALANCING EQUATIONS

• A BALANCED CHEMICAL EQUATION SHOWS THE ACTUAL NUMBER OF

MOLECULES INVOLVED IN THE REACTION

• OFTEN A CHEMICAL EQUATION ALSO INDICATES THE PHYSICAL STATES OF THE

COMPOUNDS (SOLID, LIQUID, GAS, AQUEOUS)

• 2H2 (g)+ O2 (g) 🡪 2H2O (l)

• THE IDENTITIES OF THE COMPOUNDS MUST NEVER BE CHANGED WHEN

BALANCING AN EQUATION

• THE WHOLE NUMBER INTEGERS THAT WE USE TO BALANCE THE EQUATION ARE

CALLED COEFFICIENTS

• WE NEVER WRITE THE COEFFICIENT OF "1", IT IS UNDERSTOOD
• A CHEMICAL REACTION HAS MANY POSSIBLE BALANCED EQUATIONS
• THE "BEST" BALANCED EQUATION IS THE ONE WITH THE SMALLEST

COEFFICIENTS IN FRONT OF THE COMPOUNDS

• TRICKS:

•START WITH POLYATOMIC IONS

•BALANCE O LAST AND H SECOND TO LAST

•WHEN THERE IS HYDROXIDE ON ONE SIDE AND WATER ON THE OTHER, CHANGE
H2O TO H-OH

•WHEN NECESSARY DOUBLE ALL COEFFICIENTS TO GET AN EVEN NUMBER

Page 4

Page 5

Page 11

Multiple Choice

What are the numbers that you CANNOT change in a chemical equation? 

• Coefficient

• Products

• Reactants

• Subscripts

Multiple Choice

Complete the sentence.

During a chemical reaction, atoms ________.

• can appear

• can disappear

• get rearranged

• stop moving and vibrating

​open this week’s classwork document on GC

Some text here about the topic of discussion