Physical Science

Ms. Cilli

November 29/30, 2011

DESCRIBING REACTIONSPART 1

Physical Science pages 192-198

• Interpret chemical equations in terms of reactants, products, and conservation of mass.

• Balance chemical equations by manipulating coefficients.

Chapter Notes/Study Guide

• Starting this chapter I will be providing you with a basic outline for you to take notes with

• Hopefully it will help with retention from class to class and studying for the test

• You will need to need to type the notes in the document or print it and write on it

• It will be due prior to the test for points

Physical Science pages 192-198

What is happening? Physical or Chemical Change?

What are three signs that a chemical reaction is occurring?

1.

2.

3.

Physical Science pages 192-198

CHEMICAL EQUATIONS

Reactants Products

Reactant is the name we give to the stuff we start

out with

Product is the name we give to the stuff

we end up with

Physical Science pages 192-198

Law of Conservation of mass

•Mass is neither created nor destroyed in a chemical reaction

Physical Science pages 192-198

Conservation of Mass

Steps to balancing equations

Count the number of each type of atom on

the reactant side

Count the number of each type of atom on

the product side

Compare the number on the reactant side with the numbers on

the product side

Change the coefficient of a

molecule to try and make the numbers

even

Are they all the same?

No

YesEquation is Balanced!

Physical Science pages 192-198

Example One

Cu + O2 -> CuOReactants Products

Cu

O

Physical Science pages 192-198

Rocket fuel

N2H4 + O2 -> N2 + H2O

Reactants Products

N

O

H

And Another One

Na + H2O -> NaOH + H2

Reactants Products

Na

H

O

Practice makes permanant!

HCl + CaCO3 -> CaCl2 + CO2 + H2O

Reactants ProductsCClCaOH

Physical Science pages 192-198

Got it?!?!

Al + Cl2 -> AlCl3

Reactants Products

Al

Cl

Physical Science pages 192-198

YOUR TURN

• Balance the three equations on the next slide.

• You will need to complete one of the equations

• Call me in when you are done

Zn + HCl ---> ZnCl2 + H2

KClO3 ---> KCl + O2

S8 + F2 ---> SF6

Answers….Zn + 2HCl ---> ZnCl2 + H2

2KClO3 ---> 2KCl + 3O2

S8 + 24F2 ---> 8SF6

Practice Site

• http://www.preparatorychemistry.com/balancing_equations_tutorial.htm

• http://education.jlab.org/elementbalancing/index.html

Closure

1. The substances that are present before a chemical reaction takes place are called _________ .

A. Reactants

B. Products

C. Coefficients

D. Elements

2. Which of the following is a balanced equation for the synthesis of NaBr from Na and Br2 ?

A. Na + Br2 NaBr

B. 2Na + Br2 NaBr

C. Na + Br2 2NaBr

D. 2Na + Br2 2NaBr

T/Th Assignment: MWF

• Independent Practice:– Read section 7.1– Answer the review questions and define

the vocabulary words

• Homework:– Section 7.1 HW – Due Wednesday, November 30th by 8PM

MWF Assignment: MWF

• Independent Practice:– Read section 7.1– Answer the review questions and define

the vocabulary words

• Homework:– Section 7.1 HW – Due Thursday, December 1st by 8PM