2.C – Conserving Matter

Do Now How many and what type of atoms are in the following examples: CH 4 4NH 3 6Ca(OH) 2

Objectives 1. SWBAT define the law of conservation of mass. 2. SWBAT review reactants, products, coeiffients, and determining the number of atoms in a given formula. 3. SWBAT balance chemical equations with a partner.

When a car’s gas empties, where do the atoms in the gasoline go?

Keeping Track of Atoms Law of Conservation of Matter: Matter is neither created nor destroyed. Since chemical reactions cannot create or destroy atoms, chemical equations representing the reactions must always be BALANCED.

Atomic Perspective: C O 2  CO 2 1 Carbon atom 1 oxygen molecule  1 carbon dioxide molecule 1.What are the reactants in this chemical equation? 2.What are the products in this chemical equation? 3.Are there the same number of atoms on both sides of the equation? a.Where any atoms destroyed or created? b.Was the Law of Conservation of Matter maintained?

2 Cu (s) + O 2 (g)  2 CuO (s) COEFFICIENTS - indicates the number of units of each substance involved. 1.Does the oxygen molecule have a coefficient? 2.What do the subscripts represent? 3.Can subscripts be removed from chemical equations?

How do we Balance Equations? 2 H 2 + O 2  2 H 2 O Subscripts Coefficients # of atoms in a compound Number of compounds in the reaction Subscripts balance charges within a compound. Coefficients balance atoms in an equation

What do Coefficients Really Mean? CH O 2  CO H 2 O Total: 1 C 4 H 4 O Total: 1 C 4 H 4 O The equation is balanced.

Make an atom inventory for the following equation Al 2 O 3 + HCl -> AlCl 3 + H 2 O Is it Balanced?

SWBAT Practice balancing equations in groups.

Taken from Kelly Deters Make a table of elements _____ How to Balance By Inspection: 1 Reactants Products H O C CH4H4 + O2O2  H2H2 OCO2O2 +_____

Taken from Kelly Deters 2 Count the number of each element or ion on the reactants and products side. _____ How to Balance By Inspection: Reactants Products H O C11 CH4H4 + O2O2  H2H2 OCO2O2 +_____ Don’t forget to add all the atoms of the same element together— even if it appears in more than one compound!

Taken from Kelly Deters 3 Each time you add a coefficient, update your table with the new quantities of each atom. Add coefficients to balance the numbers _____ 2 How to Balance By Inspection: Reactants Products H O C CH4H4 + O2O2  _____H2H2 OCO2O2 +

Taken from Kelly Deters 4 Filling each coefficient location lets you and the grader know that you finished the problem rather than you left some blank because you weren’t done! Place a “1” in any empty coefficient location _____ 2 How to Balance By Inspection: Reactants Products H O C CH4H4 + O2O2  _____H2H2 OCO2O2 +

Taken from Kelly Deters Choosing the Order of Balancing Save for later Elements that are uncombined Save for later Elements that appear more than 1 time per side Start Elements that appear only 1 time per side Start Elements in most complicated molecules How do you know what order to balance in? Pb + PbO 2 + H +  Pb 2+ + H 2 O To balance this equation, use the order: O, H, Pb

Taken from Kelly Deters _____ How is Balancing Affected by Order? What happens if we balance in the order determined in the last slide? Reactants Products H Pb O _____ 1212Pb +O2O2  H2H2 OPb 2+ + H+H+ _____ O, H, Pb

Taken from Kelly Deters 2 _____ What about a different order? How is it different if we balance in a different order? Reactants Products O Pb H1 2 2 _____ 1212Pb +O2O2  H2H2 OPb 2+ + H+H+ _____  You’ll still get to the correct answer, but it will take longer and be more complicated! H, O, Pb

Taken from Kelly Deters Let’s Practice #1 Example: Balance the following equation __ HCl + __ Ca(OH) 2  __ CaCl 2 + __ H 2 O

Taken from Kelly Deters Let’s Practice #1 Example: Balance the following equation __ HCl + __ Ca(OH) 2  __ CaCl 2 + __ H 2 O 2112 HOH Did you see the “OH” polyatomic ion & change H 2 O to HOH?

Taken from Kelly Deters Let’s Practice #2 Example: Balance the following equation __ H 2 + __ O 2  __ H 2 O

Taken from Kelly Deters Let’s Practice #2 Example: Balance the following equation __ H 2 + __ O 2  __ H 2 O 212

Taken from Kelly Deters Let’s Practice #3 Example: Balance the following equation __ Fe + __ O 2  ___ Fe 2 O 3

Taken from Kelly Deters Let’s Practice #3 Example: Balance the following equation __ Fe + __ O 2  ___ Fe 2 O 3 432

Homework Pg. 181 # 6-9

Do Now Balance the following equations: __Cu +__AgNO 3 -> __Cu(NO 3 ) 2 + __Ag ___NaClO 3 --> ___NaCl + ___O 2

Objectives 1. SWBAT define mole, representative particle, and molar mass. 2. SWBAT calculate the molar mass of substances.

Adopted from "Chemistry You Need to Know" by Kelly Deters C.5 The Mole Concept Definition: Mole – SI unit for counting

Adopted from "Chemistry You Need to Know" by Kelly Deters What is a counting unit? You’re already familiar with one counting unit…a “dozen” “Dozen”12 A dozen doughnuts 12 doughnuts A dozen books A dozen cars A dozen people 12 books 12 cars 12 people A dozen = 12

Adopted from "Chemistry You Need to Know" by Kelly Deters How big is a mole? Enough soft drink cans to cover the surface of the earth to a depth of over 200 miles. If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles. If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

Adopted from "Chemistry You Need to Know" by Kelly Deters A Mole of Particles A Mole of Particles Contains 6.02 x particles 1 mole C = 6.02 x C atoms 1 mole H 2 O = 6.02 x H 2 O molecules 1 mole NaCl= 6.02 x NaCl “molecules” (technically, ionics are compounds not molecules so they are called formula units) 6.02 x 1023 Na+ ions and 6.02 x 1023 Cl– ions

Adopted from "Chemistry You Need to Know" by Kelly Deters What does a “mole” count in? A mole = 6.02  (called Avogadro’s number) “mole” 6.02  mole of doughnuts 6.02  doughnuts 1 mole of atoms 1 mole of molecules 6.02  atoms 6.02  molecules 6.02  = 602,000,000,000,000,000,000,000 This means a 12 ounce bottle of water would have 19.7 “moles” of water…a much easier-to-work-with number!

Adopted from "Chemistry You Need to Know" by Kelly Deters Molar Mass

Adopted from "Chemistry You Need to Know" by Kelly Deters Definition Molar Mass – The mass for one mole of an atom or molecule. Other terms commonly used for the same meaning: Molecular Weight Molecular Mass Formula Weight Formula Mass

Adopted from "Chemistry You Need to Know" by Kelly Deters Mass for 1 mole of atoms The average atomic mass = grams for 1 mole ElementMass 1 mole of carbon atoms g 1 mole of oxygen atoms 1 mole of hydrogen atoms g 1.01 g Unit for molar mass: g/mole or g/mol Average atomic mass is found on the periodic table

Adopted from "Chemistry You Need to Know" by Kelly Deters Molar mass for molecules The molar mass for a molecule = the sum of the molar masses of all the atoms

Adopted from "Chemistry You Need to Know" by Kelly Deters Calculating a Molecule’s Mass Count the number of each type of atom Find the molar mass of each atom on the periodic table Multiple the # of atoms  molar mass for each atom Find the sum of all the masses To find the molar mass of a molecule:

Adopted from "Chemistry You Need to Know" by Kelly Deters Example: Molar Mass Example: Find the molar mass for CaBr 2

Adopted from "Chemistry You Need to Know" by Kelly Deters Example: Molar Mass Count the number of each type of atom 1 Ca Br 1 2 Example: Find the molar mass for CaBr 2

Adopted from "Chemistry You Need to Know" by Kelly Deters Example: Molar Mass Find the molar mass of each atom on the periodic table 2 Ca Br g/mole g/mole Example: Find the molar mass for CaBr 2

Adopted from "Chemistry You Need to Know" by Kelly Deters Example: Molar Mass Multiple the # of atoms  molar mass for each atom 3 Ca Br g/mole g/mole   Example: Find the molar mass for CaBr 2 = g/mole = g/mole

Adopted from "Chemistry You Need to Know" by Kelly Deters Example: Molar Mass Find the sum of all the masses 4 Ca Br g/mole g/mole = g/mole = g/mole g/mole 1 mole of CaBr 2 molecules would have a mass of g Example: Find the molar mass for CaBr 2  

Adopted from "Chemistry You Need to Know" by Kelly Deters Example: Molar Mass & Parenthesis Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis. Example: Find the molar mass for Sr(NO 3 ) 2

Adopted from "Chemistry You Need to Know" by Kelly Deters Example: Molar Mass & Parenthesis Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis g/mole g/mole   = g/mole = g/mole g/mole 1 mole of Sr(NO 3 ) 2 molecules would have a mass of g g/mole  = g/mole Sr N O Example: Find the molar mass for Sr(NO 3 ) 2

Adopted from "Chemistry You Need to Know" by Kelly Deters Let’s Practice #2 Example: Find the molar mass for Al(OH) 3

Adopted from "Chemistry You Need to Know" by Kelly Deters Let’s Practice #2 Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis g/mole 1.01 g/mole   = g/mole = 2.02 g/mole g/mole 1 mole of Al(OH) 3 molecules would have a mass of g g/mole  = g/mole Al O H Example: Find the molar mass for Al(OH) 3

Adopted from "Chemistry You Need to Know" by Kelly Deters Using Molar Mass in Conversions

Adopted from "Chemistry You Need to Know" by Kelly Deters Example: Moles to Grams Example: How many grams are in 1.25 moles of water?

Adopted from "Chemistry You Need to Know" by Kelly Deters Example: Moles to Grams 1.25 mol H 2 O = _______ g H 2 O mol H 2 O g H 2 O When converting between grams and moles, the molar mass is needed 1 mole H 2 O molecules = g H O g/mole g/mole  = 2.02 g/mole = g/mole g/mole  Example: How many grams are in 1.25 moles of water?

Adopted from "Chemistry You Need to Know" by Kelly Deters Let’s Practice #3 Example: How many moles are in 25.5 g NaCl?

Adopted from "Chemistry You Need to Know" by Kelly Deters Let’s Practice # g NaCl = _______ mole NaCl g NaCl mole NaCl mole NaCl molecules = g Na Cl g/mole g/mole  = g/mole = g/mole g/mole  Example: How many moles are in 25.5 g NaCl?

Adopted from "Chemistry You Need to Know" by Kelly Deters Example: Grams to Molecules Example: How many molecules are in 25.5 g NaCl?

Adopted from "Chemistry You Need to Know" by Kelly Deters 25.5 g NaCl Example: Grams to Molecules = _________ molecules NaCl g NaCl mol NaCl  mol = 6.02  molecules 1 moles NaCl molecules = g Na Cl g/mole g/mole  = g/mole = g/mole g/mole  mol NaCl molecules NaCl 6.02  Example: How many molecules are in 25.5 g NaCl?

Do Now Solve the following problem: How many moles are in 6.7 g of NaCl? A. Given:Unknown (attain): B. What is your conversion factor? C. Solve:

Objectives SWBAT practice conversions between moles and grams SWBAT practice conversions between moles and molecules

Adopted from "Chemistry You Need to Know" by Kelly Deters Let’s Practice #4 Example: How many grams is a sample of 2.75 × molecules of SrCl 2 ?

Adopted from "Chemistry You Need to Know" by Kelly Deters 2.75 × molecules SrCl 2 Let’s Practice #4 = _________ g SrCl 2 molecules SrCl 2 mol SrCl × mol = 6.02  molecules 1 moles SrCl 2 molecules = g Sr Cl g/mole g/mole  = g/mole = g/mole g/mole  mol SrCl 2 g SrCl Example: How many grams is a sample of 2.75 × molecules of SrCl 2 ?

REMEMBER: If you are going between moles and mass use MOLAR MASS. 1 mole molar mass (g) molar mass (g) 1 mole If you are going between moles and molecules (atoms) use AVOGADROS NUMBER X molecules 1 mole. 1 mole 6.02 X molecules

Do Now Solve the following problem: How many molecules are in 0.8 moles of NaCl? A. Given:Unknown (attain): B. What is your conversion factor? C. Solve:

Objectives SWBAT practice conversions between moles and grams SWBAT practice conversions between moles and molecules

Adopted from "Chemistry You Need to Know" by Kelly Deters THINK-PAIR-SHARE 1. How many moles are in 2.3 X molecules of NaCl? 2. How many moles are in 6.8 X molecules of CO 2 ? 3. How many molecules are in 2.3 moles of HCl?

GRAMS to MOLECULES How many molecules are in 4.6 grams of HCl?

Do Now Solve the following problem: How many moles are in 2.8 g of HCl? A. Given:Unknown (attain): B. What is your conversion factor? C. Solve:

Objective 1. SWBAT review problems where molar mass converts between moles and grams. 2. SWBAT determine molar relationships amount reactants and products in a chemical equation.

Steps to Solving Equations and Molar Relationships 1. Balance the equation. 2. State the GIVEN and what you want to ATTAIN (UNKOWN) 3. Figure out conversions. 4. SOLVE!

WORKSHEET PROBLEM #1 MOLES TO MOLES 2Mg + O 2 -> 2MgO How many moles of Mg are needed to produce 6 moles of MgO? How many moles of O 2 are needed to produce 4 moles of MgO? How many moles of MgO will be produced when 7 moles O 2 enter the reaction?

WORKSHEET PROBLEM #1 MOLES TO MOLES to Grams 2H 2 O 2 -> 2H 2 O + O 2 How many grams of H 2 O 2 are needed to produce 6 moles of O 2 ?

DO NOw For the following equation: 2Cu + O 2 -> 2CuO 1. How many moles of Cu are needed to react with 15 moles O 2 ? 2. How many moles of CuO produced when 11 moles Cu react with sufficient O 2 ?

Objectives SWBAT calculate moles of product and moles of reactants. SWAT answer questions on molar mass, g to molecules, and stoichometry.

For the following reaction: ___C 5 H 12 + ___O 2 --> ___CO 2 + ___H 2 O If 10 moles of C 5 H 12 enter the reaction, how many moles of H 2 O are produced? If 13 moles CO 2 are produced, how many moles O 2 went in? If 10 moles of C 5 H 12 enter the reaction, how many grams of H 2 O are produced?

Think-Pair-Share Pg. 166 #1-4

Do Now 2Cu + O 2 -> 2CuO 1. How many moles of Cu are needed to react with 5.6 moles O 2 ? 2. How many grams of Cu will be needed to react with 5.6 moles O 2 ?

Objectives 1. SWBAT calculate percent compositions. 2. SWBAT explain why knowledge of percent compositions is important to the mining process.

Percent Composition Percent by mass of each material found in a formula unit. Ex. In Cu 2 S, it is 80% copper.

Determining Percent Composition 1. Find the molar mass of the formula unit. 2. Find the percentage by dividing the part by the whole and multiplying by 100.

Example

Let’s Try this one Find the percent oxygen in the following formulas: CO 2 C 6 H 12 O 6

Think-Pair-Share

How is percent composition important when mining metals? How is it important when selecting your metal for your coin?

Homework Read Pg. 168 #1-4

Do Now What percent of oxygen is found in Calcium Nitrate? Ca(NO 3 ) 2

Objectives SWBAT answer questions to help them review for their upcoming test on chapter 2.C SWBAT retrieve copper from it’s ore and answer questions on the lab.

C.12. Conservation in the Community Renewable Resources: replenished by natural processes Ex. Water, air, soil, plants, animals Nonrenewable Resources: cannot be readily replenished. Ex. Natural gas, coal, oil

Conserving Resources Green Chemistry 4 Rs Rethinking Reusing Replacing Recycling