Today’s Do Now 3(NH4)2SO3 3Sn(SO3)2 5H2SO4 List the names of the elements in each compound or molecule and how many atoms of each element exist 3(NH4)2SO3 3Sn(SO3)2 5H2SO4

1. 3(NH4)2SO3 6 nitrogen atoms 24 hydrogen atoms 3 sulfur atoms Today’s Do Now 1. 3(NH4)2SO3 6 nitrogen atoms 24 hydrogen atoms 3 sulfur atoms 9 oxygen atoms

Today’s Do Now 2. 3Sn(SO3)2 3 tin atoms 6 sulfur atoms 18 oxygen atoms

3. 5H2SO4 10 hydrogen atoms 5 sulfur atoms 20 oxygen atoms Today’s Do Now 3. 5H2SO4 10 hydrogen atoms 5 sulfur atoms 20 oxygen atoms

Law of conservation of mass

Today’s Game Plan 5 minutes 15 minutes 20 minutes 10 minutes Do Now 10 minutes Law of Conservation of Mass 15 minutes Practice, Practice, Practice 20 minutes Balancing Equations Exit Ticket 5 minutes

By the end of today’s class period, I will be able to… Understand and apply the law of conservation of mass

Quick Review

Law of Conservation of Mass Matter cannot be created or destroyed in a chemical reaction Mass Reactants = Mass Products

Law of Conservation of Mass All the atoms of the reactants are still present in the products; they’ve just been rearranged The reaction between methane and oxygen

Because of the Law of Conservation of Mass… An equation must be balanced. It must have the same number of atoms of the same element on both sides.

Chemical Equations must be Balanced 4 Al(s) + 3 O2(g) 2 Al2O3(s) 4 g Al + 3 g O2 yield 2 g Al2O3 This equation means: 4 Al atoms + 3 O2 molecules  2 molecules of Al2O3 or 4 Al moles + 3 O2 moles  2 moles of Al2O3 108 g Al + 96 g O2 = 204 g Al2O3

Open vs. Closed Systems Open System: reaction taking place in an open system can exchange matter with its surroundings Closed System: reaction taking place in a closed system cannot exchange matter with its surroundings

Baking Soda and Vinegar An open vs. closed system Reactants Products Mass of E-flask 1 and balloon Mass of E-flask 2

Write.Pair.Share How can you explain to someone that the Law of Conservation of Mass holds true for both Erlenmeyer flasks??

Today’s Game Plan 5 minutes 15 minutes 20 minutes 10 minutes Do Now 10 minutes Law of Conservation of Mass 15 minutes Practice, Practice, Practice 20 minutes Balancing Equations Exit Ticket 5 minutes

Let’s Get Together! Law of Conservation of Mass Problems You will work with a different member of the class on each of the problems Record the name of the person you worked with in the box Done early??? Try to balance the chemical equations on the bottom of the back page

Today’s Game Plan 5 minutes 15 minutes 20 minutes 10 minutes Do Now 10 minutes Law of Conservation of Mass 15 minutes Practice, Practice, Practice 20 minutes Balancing Equations Exit Ticket 5 minutes

By the end of the class period today I will be able to… Use the law of conservation of mass to balance chemical equations

Why do we balance equations? Chemical equations must be balanced to obey the law of conservation of mass (atoms are not created or destroyed, just rearranged)

How do I balance an equation? To balance an equation, you may only change coefficients, not subscripts (changing subscripts would change the identity of the compound)

The ‘Best’ Balanced Equation The ‘best’ balanced equation is the one with the smallest whole number coefficients. 2Al + 3H2SO4  Al2(SO4)3 + 3H2 Instead of 4Al + 6H2SO4  2Al2(SO4)3 + 6H2

Does the Equation obey the Law of Conservation of Mass? Al + H2SO4  Al2(SO4)3 + H2 Equation #2: Pb(NO3)2 + H2S  PbS + HNO3

4 Balancing ‘Tricks’! 1. Start with the most complicated molecule 2. You cannot change subscripts! 3. Leave individual elements until last (especially Oxygen and Hydrogen) 4. Treat polyatomic ions as though they are one entity if they appear on both sides of the equation

Class Example Al + H2SO4  Al2(SO4)3 + H2

Today’s Game Plan 5 minutes 15 minutes 20 minutes 10 minutes Do Now 10 minutes Law of Conservation of Mass 15 minutes Practice, Practice, Practice 20 minutes Balancing Equations Exit Ticket 5 minutes

We talkin’ about Practice?? Guided Practice will assume the following cycle: 1. Two minutes to work independently 2. One minute to work with your neighbor 3. One minute for me to cold call students for different portions of the answer/how you discovered the answer.

You Try… ____ NaClO3  ____ NaCl + ____ O2 ___Fe(s) + ___O2(g) + ___H2O(ℓ) → ___Fe(OH)2(s)

___C8H6 + __O2 → ___CO2 + ___H2O Class Examples ___C8H6 + __O2 → ___CO2 + ___H2O

We talkin’ about Practice?? Guided Practice will assume the following cycle: 1. Two minutes to work independently 2. One minute to work with your neighbor 3. One minute for me to cold call students for different portions of the answer/how you discovered the answer.

___C2H5OH(l) + __O2(g)  __CO2(g) + __H2O(g) You Try… ___C2H5OH(l) + __O2(g)  __CO2(g) + __H2O(g)

__Sc2O3 + __Cl2 + __S2Cl2 __ScCl3 + __SOCl2 Class Examples __Sc2O3 + __Cl2 + __S2Cl2 __ScCl3 + __SOCl2

Today’s Game Plan 5 minutes 15 minutes 20 minutes 10 minutes Do Now 10 minutes Law of Conservation of Mass 15 minutes Practice, Practice, Practice 20 minutes Balancing Equations Exit Ticket 5 minutes

Homework: