Counting Atoms and Balancing Chemical Equations

Elements, Compounds, Mixtures Hydrogen is an element. Oxygen is an element. When hydrogen and oxygen bond they make the compound water. When salt and water are combined, a mixture is created. Compounds in mixtures retain their individual properties. The ocean is a mixture.

Elements, compounds, and mixtures Elements are pure substances. When the subatomic particles of an element are separated from its atom, it no longer retains the properties of that element. Mixtures can be separated by physical means. Compounds can only be separated by chemical means.

Identifying Compounds Each new element is identified by a capital letter Example: H2SO4 The elements in Sulfuric Acid Hydrogen Sulfur Oxygen

Subscripts C12H22O11 There are 12 atoms of Carbon There are 22 atoms of Hydrogen There are 11 atoms of Oxygen If there is not a subscript listed, it is understood to be 1. Example: NaCl There is one atom of Sodium There is one atom of Chlorine

NaHCO3 HCl You Practice! Hydrogen – 1 Chlorine - 1 Sodium – 1 Carbon – 1 Oxygen -3 HCl Hydrogen – 1 Chlorine - 1

There are times you will see a compound with parenthesis. Pb(NO3)2 The 2 after the parenthesis indicates there are two sets of the parenthesis. Pb(NO3) (NO3) So, in counting the atoms, you would have the following: Lead – 1 Oxygen - 6 Nitrogen -2

(NH4)3PO4 Mg(OH)2 You Practice!! Nitrogen – 3 Magnesium – 1 Hydrogen – 12 Phosphorus – 1 Oxygen – 4 Mg(OH)2 Magnesium – 1 Oxygen – 2 Hydrogen – 2

Coefficient 2H2SO4 This means there are 2 compounds of Sulfuric Acid. Think: H2SO4 H2SO4 Counting the atoms: Hydrogen – 4 Sulfur – 2 Oxygen - 8

3H3PO4 2H2O You Practice!! Hydrogen – 9 Hydrogen – 4 Phosphorus – 3 Oxygen - 12 2H2O Hydrogen – 4 Oxygen - 2

Got It????

Movin' On!!

Chemical Equations Chemical equations express what is happening in a chemical reaction using symbols. 2K + Cl2 2KCl Reactant Product yields

Law of Conservation of Mass In a chemical reaction, matter cannot be created or destroyed. It can only be changed. Therefore the Reactants must equal the Products for the equation to be balanced

What does that mean?? The reactants MUST contain the same elements and the same number of each element as the product. BUT they CAN be in different compounds.

HUH????? H2 + O2 H2O Reactants Products H = 2 H = 2 O = 2 O = 1 This cannot happen. An oxygen atom cannot be destroyed.

So what do we do? The chemical equation must be written according to the law. AGAIN --- HUH??? H2 + O2 H2O is the production of water. Well, how it actually happens in nature is this…. 2H2 + O2 2H2O Reactants: Products: H = 4 H = 4 O = 2 O = 2

Do I Need to Know How to Balance? NOT YET. You need to be able to recognize if the chemical reaction follows the law of conservation of mass. Na + O2 Na2O Mg + 2HCl MgCl2 + H2 NOPE YUP!!

You Practice!!! NOPE YUP YUP HgO Hg + O2 Hg = Hg = O = O = N2 + 3H2 2NH3 Zn + 2HCl ZnCl2 + H2 NOPE YUP YUP

More Practice NOPE NOPE YUP K + Br2 2KBr 2Fe + O2 6Fe2O3 2Na + 2H2O 2NaOH + H2 NOPE NOPE YUP

Got It???

Balancing Chemical Equations H2 + O2 H2O Reactants: H = 2 Products: H = 2 O = 2 O = 1 What do we multiply by 1 to get 2?

Keep Going…. H2 + O2 2H2O Reactants: H = 2 Products: H = 4 O = 2 O = 2 Now the Oxygen is balanced but Hydrogen is not, so what do we multiply by 2 to get 4?

Almost There!!! 2H2 + O2 2H2O Reactants: H = 4 Products: H = 4 O = 2 O = 2 Now it is balanced!!! Congratulations, you have now learned the hardest thing we will do all year!!

Now You Practice ___HgO ___Hg + ___O2 ___K + ___Br2 ___KBr Hg = Hg = O = O = ___K + ___Br2 ___KBr K = K = Br = Br =

Last Couple… ___N2 + ___H2  ___NH3 C = C= H = H = O = O = N = N = ___C2H6 + ___O2  ___CO2 +___H2O C = C= H = H = O = O =

Warm Up 3/11 Write Q&A Why do we have to balance equations? (What law do we have to follow?)

Warm Up 3/10 Write Q&A Balance the Following: HNO3 + Ca(OH)2  Ca(NO3)2 + H2O

Warm Up 3/8 Write the Following: The Law of Conservation of Mass In a chemical reaction, matter cannot be created or destroyed. It can only be changed.

Warm Up 3/5 Write Q&A How many atoms are in 3Pb(OH)4? Pb O H

Warm Up March 4 Write Q&A The vertical columns on the periodic table are called ______________ and they correspond to the number of __________ The horizontal rows on the periodic table are called ____________ and they correspond to the number of __________

Warm Up 3/9 Is it balanced? Show your work!! Al + O2 ---> Al2O3 SiCl4 + H2O ---> H4SiO4 + HCl

What are you learning today? Monday, October 18 Go Rangers!! Students will be able to: practice counting atoms Go over Counting Atoms Worksheet Chemical Formula Practice Worksheet (in class) Grade (if time) Objective: What are you learning today? Warm Up How many atoms are in Pb(OH)4? Pb O H Take out a grading pen and Counting Atoms WS Clear everything else off your desk Things to do:

What are you learning today? Monday, October 18 Go Rangers!! Students will be able to: practice counting atoms Go over Counting Atoms Worksheet Chemical Formula Practice Worksheet (in class) Grade (if time) Objective: What are you learning today? Warm Up How many atoms are in Pb(OH)4? Pb O H Take out a grading pen and Counting Atoms WS Clear everything else off your desk Things to do:

What are you learning today? Thursday, October 21 Go Rangers!! pap Objective: What are you learning today? Students will be able to: Review the differences between Physical and Chemical Changes Go Over #1-5 Balancing Equations Activity Do #1-7 for HW 5H2 What number represents the Coefficient? ____ What number represents the Subscript? _____ What element is represented by the letter "H"? ___________ How many "H's" do you have? _____ Warm Up Things to do: Take out Worksheet from Yesterday #1-5

What are you learning today? Wednesday, October 20 Go Rangers!! pap Objective: What are you learning today? Students will be able to: use the Law of Conservation of mass to Balance Equations Grade #11-20 Balancing Equations Activity Do #1-7 for HW Balance the Following: __HNO3 +__Ca(OH)2  __Ca(NO3)2 + __H2O Warm Up Things to do: Take out a grading pen Clear everything else off your desk

What are you learning today? Wednesday, October 20 Go Rangers!! Objective: What are you learning today? Students will be able to: use the Law of Conservation of mass to Balance Equations Go over Homework #1-10 Notes on Balancing Equations Balancing Equations Worksheet #1-5 Do #11-20 on your Homework from yesterday What law do we have to follow when we are figuring if equations are balanced or not? Why? Warm Up Things to do: Take out your homework from yesterday

What are you learning today? Tuesday, October 19 Go Rangers!! Objective: What are you learning today? Students will be able to: use the skill of counting atoms to tell if an equation is balanced Notes on Balancing Equations Balancing Equations Worksheet #1-10 How many atoms are in 3Pb(OH)4? (look at what you did yesterday!!) Pb O H Warm Up Things to do: Take out a grading pen Clear everything else off your desk