CHEMICAL REACTIONS & REACTIONS &BALANCINGEQUATIONSChemistry

LEARNING OBJECTIVES TLW use the law of conservation of mass to write and balance chemical equations (TEKS 8.D TLW use the law of conservation of mass to write and balance chemical equations (TEKS 8.D TLW balance equations using 4-step “T” Chart Process, Drop Down Approach, or other method TLW balance equations using 4-step “T” Chart Process, Drop Down Approach, or other method

AGENDA Law of Conservation of Mass Law of Conservation of Mass Cooking with Chemistry – A Recipe for Success and Making Good Stuff Cooking with Chemistry – A Recipe for Success and Making Good Stuff Chemical Equations & Coefficients Chemical Equations & Coefficients Balancing Act of Reactants and Products – Balancing Act of Reactants and Products – The 4-Step “T” Chart Process The 4-Step “T” Chart Process Drop Down Approach Drop Down Approach Guided Practice Guided Practice Independent Practice Independent Practice Nuts & Bolts Lab Nuts & Bolts Lab

CONSERVATION OF MASS Total MASS of PRODUCTS EQUALS Total MASS of REACTANTS Total MASS of PRODUCTS EQUALS Total MASS of REACTANTS

CONSERVATION OF MASS Mass of WOOD and AIR before burning a fire Mass of WOOD and AIR before burning a fireEQUALS Mass of ASH and GASES after burning a fire

COOKING WITH CHEMISTRY CHEMICAL EQUATIONS ARE LIKE RECIPES They tell you QUANTITIES of INGREDIENTS (REACTANTS) and QUANTITIES of PRODUCTS

Trail Mix Ingredients (Reactants) Product 1 c. Mixed Dried Fruit- 6 c. Yummy and 1 c. Mixed Dried Fruit- 6 c. Yummy and ½ c. Raisins and/or Healthy Snack ½ c. Raisins and/or Healthy Snack Dried Cranberries Dried Cranberries 1 c. Unsalted Nuts 1 c. Unsalted Nuts peanuts, almonds, or walnuts 1 c. Shelled Seeds 1 c. Shelled Seeds sunflower, pumpkin sunflower, pumpkin ½ c. M & Ms ½ c. M & Ms 1 c. Cheerios 1 c. Cheerios 1 c. Pretzels 1 c. Pretzels

Comparing Food Recipes to Chemical Equations How are they similar? How are they similar? How are they different? How are they different?

Discovery Education Video Time link

CHEMICAL EQUATIONS NUMBER of REACTANT MOLECULES needed to MAKE a CERTAIN NUMBER of PRODUCT MOLECULES 2Na + Cl > 2NaCl

BALANCED EQUATIONS Correct RATIOS of Molecules are shown as COEFFICIENTS in BALANCED EQUATIONS Correct RATIOS of Molecules are shown as COEFFICIENTS in BALANCED EQUATIONS 2H 2 + O > 2H 2 O 2H 2 + O > 2H 2 O Coefficients must be whole numbers Coefficients must be whole numbers

In CHEMICAL REACTIONS, BONDS BREAK and REFORM ATOMS are REARRANGED REACTANTS CHANGE to FORM NEW PRODUCTS with DIFFERENT PROPERTIES

Use FORMULAS and SYMBOLS to show REACTION Use FORMULAS and SYMBOLS to show REACTION CONSERVATION OF ATOMS CONSERVATION OF ATOMS Number of each type of atom in REACTANTS and PRODUCTS MUST BALANCE Number of each type of atom in REACTANTS and PRODUCTS MUST BALANCE CHEMICAL EQUATIONS

How to Balance an Equation A. Rules to remember 1. You can not change the chemical formula: NaCl must stay NaCl 2. You must leave subscripts alone: AlCl 3 stays AlCl 3 You can NOT change the 3

3. You can only add coefficients a. coefficients are numbers that go in front of the chemical formula b. 3 FeCl Al the 3 and 2 are coefficients.. (note - 1 is not written down)  2 AlCl Fe

Tips Balance most complex compounds or metals first (look at charges) Balance most complex compounds or metals first (look at charges) Balance non-metals next, except O & H Balance non-metals next, except O & H Balance O and H last Balance O and H last Look for polyatomic groupings and balance those as groups Look for polyatomic groupings and balance those as groups The polyatomic group must be on both sides of equation The polyatomic group must be on both sides of equation Examples: NO 3, OH, SO 4 Examples: NO 3, OH, SO 4 Al 2 (SO 4 ) 3 + Ca(OH) 2  Al(OH) 3 + CaSO 4

Tips If you have water (H 2 O), you can rewrite it as H and OH separately If you have water (H 2 O), you can rewrite it as H and OH separately You can have an interim step of coefficient with decimal…. But must multiply through to get whole numbers as final balancing act You can have an interim step of coefficient with decimal…. But must multiply through to get whole numbers as final balancing act

Chemical Equations Remember the Criss-Cross Rule when working with compounds Remember the Criss-Cross Rule when working with compounds Balance the charges of ions so molecule has zero (neutral) charge Balance the charges of ions so molecule has zero (neutral) charge Begin with the positive one first (Fe +3 ) Begin with the positive one first (Fe +3 ) Then bring in negative ion (O -2 ) Then bring in negative ion (O -2 ) Criss-cross the numbers  Fe 2 O 3 Criss-cross the numbers  Fe 2 O 3

Use the criss-cross approach of balancing charges Use the criss-cross approach of balancing charges Example: Example: Al 2 (SO 4 ) 3 + 3Ca(OH) 2  2Al(OH) 3 + 3CaSO 4 Al 2 (SO 4 ) 3 + 3Ca(OH) 2  2Al(OH) 3 + 3CaSO 4

Group Practice Recognizing How Balanced Equations Look Recognizing How Balanced Equations Look Recap Rules and Tips Recap Rules and Tips link

Processes to Use Some people can see how to balance equations Some people can see how to balance equations Other folks have developed methods such as: Other folks have developed methods such as: 4-Step “T” Chart Process 4-Step “T” Chart Process Drop Down Approach Drop Down Approach

Draw T-chart

4. Recount

Drop Down Approach N 2 + O 2  NO 2 Re-write to visually show number of atoms using symbols in each molecular compound NN + OO  NOO NN OONOO OONOO OONOO Count rows and you have coefficients N 2 + 2O 2  2NO 2

Internet Drop Down Approach Game - Classic Chembalancer Internet Drop Down Approach Game - Classic Chembalancer Balancer/ques1.htm Balancer/ques1.htm Balancer/ques1.htm Balancer/ques1.htm

Group Practice Together let’s work through Guided Reading and Study Workbook pages 79 & 80 Together let’s work through Guided Reading and Study Workbook pages 79 & 80

More Group Practice P 4 + 5O 2  ___ P 2 O 5 P 4 + 5O 2  ___ P 2 O 5 4Fe + 3O 2  ___ Fe 2 O 3 4Fe + 3O 2  ___ Fe 2 O 3 CS 2 + 3O 2  ___ CO 2 + ___ SO 2 CS 2 + 3O 2  ___ CO 2 + ___ SO 2 ___N 2 O 5 + __ NO  4N 2 + 9O 2 + NO 3 ___N 2 O 5 + __ NO  4N 2 + 9O 2 + NO 3 __ KOH + __ HCl  KCl + H 2 O __ KOH + __ HCl  KCl + H 2 O

More Fun with Balancing Equations Internet Game Internet Game dex.html dex.html dex.html dex.html

Individual Practice Practice Sets Practice Sets Balancing Equations – 2 Balancing Equations – 2 Balancing Equations – 2 Balancing Equations – 2 Balancing Equations and Identifying Reactions - 3 Balancing Equations and Identifying Reactions - 3 Balancing Equations and Identifying Reactions - 3 Balancing Equations and Identifying Reactions - 3 Hard copy of other worksheets Hard copy of other worksheets