Chemical Reactions Chapter 7

Chapter 7 Day 1 Do Now: Chapter 7 Vocabulary OBJECTIVE: Interpret chemical reactions for reactants and products, energy needs and conservation of mass. Do Now: Chapter 7 Vocabulary TURN IN: Model Molecule Lab Today: Chapter 7 – Chemical Reactions notes Types of Chemical Reactions Cartoon Chemistry Homework: Finish Cartoon Chemistry

Unit 2 Chapter 7 Day 2 OBJECTIVE: Unit 2 Chapter 7 Day 2 OBJECTIVE: Interpret chemical reactions for reactants and products, energy needs and conservation of mass. Do Now: Types of Chemical Reactions Today: The Balancing Act packet – Notes and Worksheets Homework: Balancing Equations

Unit 2 Chapter 7 Day 3 OBJECTIVE: Interpret chemical reactions for reactants and products, energy needs and conservation of mass. Do Now: Balancing Review Today: Homework review – Balancing Equations DVD Field Trips – Chapters 6 & 7 Test review / Study Guide… What did we learn again? START Test Review packet Homework: COMPLETE Test Review packet

Unit 2 Chapter 7 Day 4 OBJECTIVE: Unit 2 Chapter 7 Day 4 OBJECTIVE: Demonstrate knowledge of matter, phase, atomic structure, the periodic table, chemical reactions and conservation of mass. Do Now: Vocabulary Bingo - Chapters 4,5,6,7 Today: Review Chemistry Unit Study Guide Spring Balance Challenge Homework: STUDY FOR CHEMISTRY UNIT TEST

Unit 2 Chapter 7 Day 5 Do Now: Do Now Folder #6-7 (8 pages) Today: OBJECTIVE: Demonstrate knowledge of matter, phase, atomic structure, the periodic table, chemical reactions and conservation of mass. Do Now: Do Now Folder #6-7 (8 pages) Today: Chemistry Unit Test Unit 2 Notebook Chap 6 & 7 (21 pages) Homework: Current Events – 2nd Chance Experiments

Extra Credit Balance Challenges ____ CoBr3 + ____ CaSO4  ____ CaBr2 + ____ Co2(SO4)3 ____ S    +   ____ HNO3       ____ H2SO4   +    ____ NO2   +   ____ H2O  ____ Cu   +  ____  HNO3    ____ Cu(NO3)2  + ____ NO   +    ____ H2O

A 2 CoBr3 + 3 CaSO4  3 CaBr2 + Co2(SO4)3 B S + 6 HNO3 -> H2SO4 + 6 NO2 + 2 H2O C 3 Cu + 8HNO3 -> 3 Cu(NO3)2 + 2 NO + 4 H2O

Chemical Reactions Chapter 7

Wednesday 11/12 and Thursday 11/13 Unit 2 Chapter 6/7 OBJECTIVE: Investigate five indicators of chemical reations. Do Now: ASK Review Today: Identifying Chemical Reaction Lab Homework: Missing Assignments for MP1?

Indicators of chemical reactions Emission of light or heat Formation of a gas Formation of a precipitate Color change Emission of odor

All chemical reactions: Create 1 or more new substances Have two parts Reactants - the substances you start with Products- the substances you end up with The reactants turn into the products. Reactants ® Products

In a chemical reaction… Bonds between atoms in reactants are broken Atoms rearrange and form new bonds in the products Atoms aren’t created or destroyed…Mass is CONSERVED in a chemical reaction..This is called… Law of Conservation of Mass

Reaction Energy All chemical reactions are accompanied by a change in energy.  It takes energy to break bonds AND energy is released when bonds are broken! Exothermic - reactions that release energy to their surroundings (usually in the form of heat) Endothermic - reactions that need to absorb heat from their surroundings to proceed.

Types of Reactions

Synthesis Reactions TWO elements combine to make one compound. (Polyatomics count as one) A + B ® AB Na + Cl2 ® NaCl Ca +O2 ® CaO SO3 + H2O ® H2SO4 We can predict the products if there are two elements. Mg + N2 ® Mg3N2

Decomposition Reactions decompose = fall apart, Falls apart into its elements Made up of only two elements one compound (reactant) falls apart into two or more elements or compounds. Usually requires energy AB ® A + B NaCl ® Na + Cl2 CaCO3 ® CaO + CO2

Single Replacement One element replaces another Reactants must be an element and a compound. Products will be a different element and a different compound. A + BC ® AC + B 2Na + SrCl2 ® Sr + 2NaCl F2 + LiCl ® LiF + Cl2

Double Replacement Two things replace each other. Usually in water solution AB + CD ® AD + CB ZnS + 2HCl ® ZnCl + H2S AgNO3 + NaCl ® AgCl + NaNO3

How to recognize which type Look at the reactants Element(E), Compound(C) E + E C E + C C + C Synthesis Decomposition Single replacement Double replacement

Examples Synthesis H2 + O2 ® H2O ® Decomposition AgNO3 + NaCl ® Double replacement Zn + H2SO4 ® Single replacement HgO ® Decomposition KBr +Cl2 ® Single replacement Mg(OH)2 + H2SO3 ® Double replacement

Examples Decomposition CaPO4 ® AgBr + Cl2 ® Single replacement Zn + O2 ® Synthesis HgO + Pb® Single replacement Cu(OH)2 + KClO3 ® Double replacement

Identifying Chemical Reactions S = Synthesis D = Decomposition SR = Single Replacement DR = Double Replacement   _____ P + O2 → P4O10 ____ Mg + O2 → MgO ____ HgO → Hg + O2 ____ Al2O3 → Al + O2 ____ Cl2 + NaBr → NaCl + Br2 ____ H2 + N2 → NH3

____ Na + Br2 → NaBr ____ CuCl2 + H2S → CuS + HCl ____ HgO + Cl2 → HgCl + O2 ____ C + H2 → CH4 ____ KClO3  →   KCl  +  O2  ____ S8 + F2 → SF6 ____ BaCl2   +   Na2 SO4 →    NaCl   + BaSO4

Balancing Act

Chemical Reactions Review… Is the process where physical and chemical properties of the original substance change into a new substance with different physical and chemical properties If there is no new substance there has been no reaction Reactants enter into the reaction Products are produced by the reaction

Chemical Reactions Review… Chemical equations describe chemical reactions using symbols and numbers. 2Na + SrCl2 ® Sr + 2NaCl Coefficients (in red) The large numbers in front of chemical formulas. The number of molecules of the substance in the reaction

Chemical Reactions Review… Chemical equations describe chemical reactions using symbols and numbers. 2Na + SrCl2 ® Sr + 2NaCl Subscripts (in Green) The small numbers to the lower right of chemical symbols Represent the number of atoms of each element is in the molecule

Chemical Reactions Review… Atoms can neither be created nor destroyed during a chemical reaction…Mass MUST remain constant You have to end up with the same number of atoms you started with, but in a different arrangement So balanced equations have the same number of atoms on each side of the YIELDS “®“ sign Law of Conservation of Mass

Balancing Chemical Equations (ALWAYS USE PENCIL) Check for DIATOMIC molecules H2 , N2 , O2 , F2 , Cl2 , Br2 , I2 , and At2 You cannot change the subscripts of these elements in an equation… whenever they are by themselves, these must be written with the subscript 2.

Balancing Chemical Equations Count the number of atoms on each side of the reaction: ___Na + ___MgCl2 ® ___Mg + ___NaCl Sodium=____ ® Sodium=____ Magnesium=____ ® Magnesium =____ Chlorine=____ ® Chlorine=____ 1 2 1

Balancing Chemical Equations Balance the metals first then the nonmetals ___Na + ___MgCl2 ® ___Mg + ___NaCl Sodium=____ ® Sodium=____ Magnesium=____ ® Magnesium =____ Chlorine=____ ® Chlorine=____ 2 2 1 2 X 2 1 X 2 X 2

Balancing Chemical Equations If they are in your equation, balance OXYGEN then HYDROGEN last Recount all atoms and check your work! Work from the bottom to top until you find any error. If every coefficient will reduce, rewrite in the simplest whole number ratio

Balancing Chemical Equations Lets try an easy one: ___H2 + ___O2 ® ___H2O Hydrogen=____ ® Hydrogen=____ Oxygen=____ ® Oxygen =____ 2 2 2 1 X 4 2 X 4 X 2

Balancing Chemical Equations Lets try one more: ___Na + ___HCl ® ___H2 + ___NaCl Sodium=____ ® Sodium =____ Hydrogen=____ ® Hydrogen=____ Chlorine=____ ® Chlorine =____ 2 2 2 1 X 2 1 2 X 2 X 2 X 2 X 2

Balancing Act ___Mg + ___O2 ® ___MgO ___Ca + ___O2 ® ___CaO ___H2O2 ® ___H2O + ___O2 ___N2 + ___H2 ® ___NH3 ___Cu2O + ___C ® ___Cu+ ___CO2

Reaction Energy Spontaneous Reactions - Reactions that proceed immediately when two substances are mixed together.  Not all reactions proceed spontaneously.  Activation Energy – the amount of energy that is required to start a chemical reaction. Once activation energy is reached the reaction continues until you run out of material to react.  

Diatomic elements There are 8 elements that never want to be alone. They form diatomic molecules. H2 , N2 , O2 , F2 , Cl2 , Br2 , I2 , and At2

What is a catalyst? A substance that can help the reactants in a chemical reaction react with each other faster Speeds up a reaction without being changed by the reaction…it does NOT become part of the reaction. Enzymes are biological or protein catalysts.

Summary of Symbols