chemistry: matter and change - taylor.k12.ky.us chem - ch 9... · chemical change. chemical change:...

77

Upload: vodung

Post on 26-Jun-2018

249 views

Category:

Documents


1 download

TRANSCRIPT

Chapter Menu

Chemical Reactions

Section 9.1 Reactions and

Equations

Section 9.2 Classifying Chemical

Reactions

Section 9.3 Reactions in Aqueous

Solutions

Exit Click a hyperlink or folder tab to view

the corresponding slides.

Section 9-1

Section 9.1 Reactions and Equations

• Recognize evidence of chemical change.

chemical change: a process involving one or more substances changing into a new substance

chemical reaction

reactant

product

chemical equation

coefficient

• Represent chemical reactions with equations.

• Balance chemical equations.

Chemical reactions are represented by balanced chemical equations.

Section 9-1

Chemical Reactions

• The process by which one or more substances are rearranged to form different substances is called a chemical reaction.

• All chemical reactions are the result of chemical changes.

http://web.jjay.cuny.edu/~acarpi/NSC/watreact.htm

Section 9-1

Chemical Reactions (cont.)

• Evidence of a chemical reaction

– Change in temperature Ex: wood burning

– Change in color Ex: leaves changing colors

– Odor forms Ex: rotting garbage

– Gas or solid forms Ex: sour milk

Section 9-1

Representing Chemical Reactions

• Chemists use statements called equations to represent chemical reactions.

• Reactants are the starting substances.

• Products are the substances formed in the reaction.

Section 9-1

Representing Chemical Reactions (cont.)

• Skeleton equations use symbols and formulas to represent the reactants and products. Al(s) + Br 2 (l) → AlBr3(s)

• Skeleton equations lack information about how many atoms are involved in the reaction.

Section 9-1

Representing Chemical Reactions (cont.)

• A chemical equation uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.

Section 9-1

Balancing Chemical Equations

• Coefficients are used to balance chemical equations.

• A coefficient in a chemical equation is the number written in front of a reactant or product.

2 H2 (g) + O2 (g) 2 H2O(l)

Hints for Balancing Chemical Equations

• Count atoms of reactants & products

• Never change or alter subscripts

• Add coefficients to balance # of atoms

• Balance H and O last!!!

• Check that coefficients are in lowest ratio!!!

Balancing Chemical Equations (cont.)

Section 9-1

Balancing Chemical Equations

• This figure shows the balanced equation for the reaction between aluminum and bromine.

Section 9-1

Balancing Chemical Equations (cont.)

Why Balance Chemical Equations???

• The most fundamental law in chemistry is the law of conservation of mass.

• Balanced equations show this law!!!

A. A

B. B

C. C

D. D

Section 9-1

A B C D

0% 0%0%0%

Section 9.1 Assessment

Which of the following is NOT a chemical reaction?

A. a piece of wood burning

B. a car rusting

C. an ice cube melting into water

D. red litmus paper turning blue

A. A

B. B

C. C

D. D

Section 9-1

A B C D

0% 0%0%0%

Section 9.1 Assessment

What is the coefficient of bromine in the equation 2Al(s) + 3Br2(l) → 2AlBr3(s)?

A. 1

B. 2

C. 3

D. 6

End of Section 9-1

Section 9-2

Section 9.2 Classifying Chemical Reactions

• Classify chemical

reactions.

metal: an element that is a solid at room temperature, a good conductor of heat and electricity, and is generally shiny

• Identify the

characteristics of

different classes of

chemical reactions.

Section 9-2

Section 9.2 Classifying Chemical Reactions (cont.)

synthesis reaction

combustion reaction

decomposition reaction

single-replacement reaction

There are four types of chemical reactions: synthesis, combustion, decomposition, and replacement reactions.

double-replacement reaction

precipitate

Section 9-2

Types of Chemical Reactions

• Chemists classify reactions in order to organize the many types.

1. A synthesis reaction is a reaction in which two or more substances react to produce a single product.

A + B AB

Section 9-2

Types of Chemical Reactions (cont.)

• When two elements react, the reaction is always a synthesis reaction.

Section 9-2

Types of Chemical Reactions (cont.)

2. In a combustion reaction, oxygen combines with a substance and releases energy in the form of heat and light.

• Heated hydrogen reacts with oxygen to produce heat and water in a combustion reaction. This is also a synthesis reaction.

Section 9-2

Decomposition Reactions

3. A decomposition reaction is one in which a single compound breaks down into two or more elements or new compounds.

AB A + B

• Decomposition reactions often require an energy source, such as heat, light, or electricity, to occur.

Section 9-2

Replacement Reactions

4. A reaction in which the atoms of one element replace the atoms of another element in a compound is called a single replacement reaction.

A + BX → AX + B

• A metal will replace a less active metal.

• A nonmetal will replace a less active nonmetal.

Section 9-2

Replacement Reactions (cont.)

• A metal will not always replace a metal in a compound dissolved in water because of differing reactivities.

• An activity series can be used to predict if reactions will occur.

Section 9-2

Replacement Reactions (cont.)

• Halogens frequently replace other halogens in replacement reactions.

• Halogens also have different reactivities and do not always replace each other.

Section 9-2

Replacement Reactions (cont.)

5. Double replacement reactions occur when ions exchange between two compounds.

• The anions trade places to form new compounds.

Section 9-2

Replacement Reactions (cont.)

• The solid product produced during a chemical reaction in a solution is called a precipitate.

• All double replacement reactions produce either water, a precipitate, or a gas.

Section 9-2

Replacement Reactions (cont.)

• This table shows the steps to write double replacement reactions.

Section 9-2

Replacement Reactions (cont.)

• This table summarizes different ways to predict the products of a chemical reaction.

A. A

B. B

C. C

D. D

Section 9-2

A B C D

0% 0%0%0%

Section 9.2 Assessment

Which of the following is NOT one of the four types of reactions?

A. deconstructive

B. synthesis

C. single replacement

D. double replacement

A. A

B. B

C. C

D. D

Section 9-2

Section 9.2 Assessment

A B C D

0% 0%0%0%

The following equation is what type of reaction?

KCN(aq) + HBr(aq) → KBr(aq) + HCN(g)

A. deconstructive

B. synthesis

C. single replacement

D. double replacement

End of Section 9-2

Section 9-3

Section 9.3 Reactions in Aqueous Solutions

• Describe aqueous solutions.

solution: a uniform mixture that might contain solids, liquids, or gases

• Write complete ionic and net ionic equations for

chemical reactions in aqueous solutions.

• Predict whether reactions in aqueous solutions will

produce a precipitate, water, or a gas.

Section 9-3

Section 9.3 Reactions in Aqueous Solutions

(cont.)

aqueous solution

solute

solvent

Double-replacement reactions occur between substances in aqueous solutions and produce precipitates, water, or gases.

complete ionic equation

spectator ion

net ionic equation

Section 9-3

Aqueous Solutions

• An aqueous solution contains one or more dissolved substances (called solutes) in water.

• The solvent is the most plentiful substance in a solution.

Section 9-3

Aqueous Solutions (cont.)

• Water is always the solvent in an aqueous solution.

• There are many possible solutes—sugar and alcohol are molecular compounds that exist as molecules in aqueous solutions.

• Compounds that produce hydrogen ions in aqueous solutions are acids.

Section 9-3

Aqueous Solutions (cont.)

• Ionic compounds can also be solutes in aqueous solutions.

• When ionic compounds dissolve in water, their ions separate in a process called dissociation.

Section 9-3

Types of Reactions in Aqueous Solutions

• When two solutions that contain ions as solutes are combined, the ions might react.

• If they react, it is always a double replacement reaction.

• Three products can form: precipitates, water, or gases.

Section 9-3

Types of Reactions in Aqueous Solutions (cont.)

• Aqueous solutions of sodium hydroxide and copper(II) chloride react to form the precipitate copper(II) hydroxide.

2NaOH(aq) + CuCl2(aq) → 2NaCl(aq) + Cu(OH)2(s)

• Ionic equations that show all of the particles in a solution as they actually exist are called complete ionic equations.

2Na+(aq) + 2OH–(aq) + Cu2+ (aq)+ 2Cl–(aq) → 2Na+(aq) + 2Cl–(aq) + Cu(OH)2(s)

Section 9-3

Types of Reactions in Aqueous Solutions (cont.)

• Ions that do not participate in a reaction are called spectator ions and are not usually written in ionic equations.

• Formulas that include only the particles that participate in reactions are called net ionic equations.

2OH–(aq) + Cu2+(aq) → Cu(OH)2(s)

Section 9-3

Types of Reactions in Aqueous Solutions (cont.)

• Some reactions produce more water molecules.

• No evidence of a chemical reaction is observable.

HBr(aq) + NaOH(aq) → H2O(l) + NaBr(aq)

• Without spectator ions H+(aq) + OH–(aq) → H2O(l).

Section 9-3

Types of Reactions in Aqueous Solutions (cont.)

• Gases that are commonly produced are carbon dioxide, hydrogen cyanide, and hydrogen sulfide.

2HI(aq) + Li2S(aq) → H2S(g) + 2LiI(aq)

Section 9-3

Types of Reactions in Aqueous Solutions (cont.)

• Another example is mixing vinegar and baking soda, which produces carbon dioxide gas.

HCl(aq) + NaHCO3(aq) → H2CO3(aq) + NaCl(aq)

• H2CO3(aq) decomposes immediately.

H2CO3(aq) → H2O(l) + CO2(g)

Section 9-3

Types of Reactions in Aqueous Solutions (cont.)

• Two reactions can be combined and represented by a single chemical reaction.

Section 9-3

Types of Reactions in Aqueous Solutions (cont.)

Reaction 1

HCl(aq) + NaHCO3(aq) → H2CO3(aq) + NaCl(aq)

Reaction 2

H2CO3(aq) → H2O(l) + CO2(g)

Combined equation

HCl(aq) + NaHCO3(aq) + H2CO3(aq) → H2CO3(aq) + NaCl(aq) + H2O(l) + CO2(g)

Overall equation

HCl(aq) + NaHCO3(aq) → H2O(l) + CO2(g) + NaCl(aq)

A. A

B. B

C. C

D. D

Section 9-3

A B C D

0% 0%0%0%

Section 9.3 Assessment

What is the solvent in an aqueous solution?

A. hydrogen

B. sodium ions

C. water

D. alcohol

A. A

B. B

C. C

D. D

Section 9-3

Section 9.3 Assessment

A B C D

0% 0%0%0%

An equation that includes only the particles that participate in a reaction is called:

A. net ionic equation

B. spectator ions

C. complete ionic equation

D. reduced ionic equation

End of Section 9-3

Resources Menu

Chemistry Online

Study Guide

Chapter Assessment

Standardized Test Practice

Image Bank

Concepts in Motion

Study Guide 1

Section 9.1 Reactions and Equations

Key Concepts

• Some physical changes are evidence that indicate a chemical reaction has occurred.

• Word equations and skeleton equations provide important information about a chemical reaction.

• A chemical equation gives the identities and relative amounts of the reactants and products that are involved in a chemical reaction.

• Balancing an equation involves adjusting the coefficients until the number of atoms of each element is equal on both sides of the equation.

Study Guide 2

Section 9.2 Classifying Chemical Reactions

Key Concepts

• Classifying chemical reactions makes them easier to understand, remember, and recognize.

• Activity series of metals and halogens can be used to predict if single-replacement reactions will occur.

Study Guide 3

Section 9.3 Reactions in Aqueous Solutions

Key Concepts

• In aqueous solutions, the solvent is always water. There are many possible solutes.

• Many molecular compounds form ions when they dissolve in water. When some ionic compounds dissolve in water, their ions separate.

• When two aqueous solutions that contain ions as solutes are combined, the ions might react with one another. The solvent molecules do not usually react.

• Reactions that occur in aqueous solutions are double-replacement reactions.

A. A

B. B

C. C

D. D

Chapter Assessment 1

A B C D

0% 0%0%0%

The law of conservation of mass requires what in a chemical reaction equation?

A. both sides of the equation to contain the same substances

B. the reactants to have the same amount of molecules as the products

C. both sides to have the same amount of atoms of each element

D. the products to have fewer molecules than the reactants

A. A

B. B

C. C

D. D

Chapter Assessment 2

A B C D

0% 0%0%0%

A reaction that gives off heat is what type of reaction?

A. single replacement reaction

B. double replacement reaction

C. synthesis reaction

D. combustion reaction

A. A

B. B

C. C

D. D

Chapter Assessment 3

A B C D

0% 0%0%0%

Ions that are present in a solution and do not participate in a chemical reaction when another substance is added are called ____.

A. spectator ions

B. reactants

C. products

D. net ions

A. A

B. B

C. C

D. D

Chapter Assessment 4

A B C D

0% 0%0%0%

A double replacement reaction produces all of the following except ____.

A. gases

B. solids

C. light

D. water

A. A

B. B

C. C

D. D

Chapter Assessment 5

A B C D

0% 0%0%0%

What type of reaction is the following?

2H2O(l) + energy → H2(g) + O2(g)

A. synthesis reaction

B. decomposition reaction

C. combustion reaction

D. replacement reaction

A. A

B. B

C. C

D. D

STP 1

A B C D

0% 0%0%0%

What type of reaction is the following?

2H2(g) + O2(g) → 2H2O(l)

A. replacement reaction

B. synthesis

C. combustion reaction

D. double replacement reaction

A. A

B. B

C. C

D. D

STP 2

A B C D

0% 0%0%0%

A precipitate forms in a double replacement reaction only if:

A. the reactivities of the compounds differ

B. the new compound is denser than water

C. the new compound is soluble in water

D. the new compound is not soluble in water

A. A

B. B

C. C

D. D

STP 3

A B C D

0% 0%0%0%

A ____ is a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.

A. word equation

B. skeleton equation

C. chemical equation

D. balanced equation

A. A

B. B

C. C

D. D

STP 4

A B C D

0% 0%0%0%

Predict the type of reaction.

LiBr2 (aq) + 2NaOH (aq) → ____

A. synthesis reaction

B. combustion reaction

C. single replacement reaction

D. double replacement reaction

A. A

B. B

C. C

D. D

STP 5

A B C D

0% 0%0%0%

Which reactions are essentially the opposite of synthesis reactions?

A. single-replacement

B. decomposition

C. combustion

D. double-replacement

IB Menu

Click on an image to enlarge.

IB 1

IB 2

IB 3

IB 4

IB 5

IB 6

IB 7

IB 8

IB 9

IB 10

IB 11

IB 12

Help

Click any of the background top tabs to display the respective folder.

Within the Chapter Outline, clicking a section tab on the right side of the screen will bring you to the first slide in each respective section.

Simple navigation buttons will allow you to progress to the next slide or the previous slide.

The “Return” button will allow you to return to the slide that you were viewing when you clicked either the Resources or Help tab.

The Chapter Resources Menu will allow you to access chapter specific resources from the Chapter Menu or any Chapter Outline slide. From within any feature, click the Resources tab to return to this slide.

To exit the presentation, click the Exit button on the Chapter Menu slide or hit Escape [Esc] on your keyboards while viewing any Chapter Outline slide.

End of Custom Shows

This slide is intentionally blank.