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
Represent chemical reactions with equations.
Balance chemical equations.
chemical reaction
reactant
product
chemical equation
coefficient
Chemical reactions are represented by balanced chemical equations.
Section 9-1

2. Chemical Reactions
The process by which one or more substances are rearranged to form different substances is called a ___________________________
This involves a chemical change – where you change the identity of the substance.
Section 9-1

3. Chemical Reactions (cont.)
Evidence of a chemical reaction
Change in temperature
Exothermic (higher T) vs Endothermic (lower T)
Change in color
Odor, gas, or bubbles may form.
Form a precipitant (????)
Emission of Light
Section 9-1

4. ______________are the starting substances.
Chemists use statements called equations to represent chemical reactions.
______________are the starting substances.
______________are the substances formed in the reaction.
Section 9-1

5. Representing Chemical Reactions (cont.)
In word equations, aluminum(s) + bromine(l) → aluminum bromide(s) reads as “aluminum and bromine react to produce aluminum bromide”.
Skeleton equations use symbols and formulas to represent the reactants and products. Al(s) + Br(l) → AlBr3(s)
Skeleton equations lack information about how many atoms are involved in the reaction.
Section 9-1

6. Representing Chemical Reactions (cont.)
A _____________________is a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.
Section 9-1

7. Balancing Chemical Equations
This figure shows the balanced equation for the reaction between aluminum and bromine.
Section 9-1

8. Balancing Chemical Equations (cont.)
A ______________________in a chemical equation is the number written in front of a reactant or product, describing the lowest whole-number ratio of the amounts of all the reactants and products.
So what are the coefficients on the previous reaction?
*Table 9.2 in book shows steps for balancing equations
Section 9-1

9. Balanced equations show this law.
Why balance equations?
One of the most fundamental laws in chemistry is the law of conservation of mass.
Balanced equations show this law.
A balanced equation is also like a recipe.
Section 9-1

10. Balancing Chemical Equations (cont.)
Section 9-1

11. A B C D 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 B C D
Section 9-1

12. A B C D 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 A B C D
Section 9-1

13. 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

14. Section 9.2 Classifying Chemical Reactions (cont.)
synthesis reaction
combustion reaction
decomposition reaction
single-replacement reaction
double-replacement reaction
precipitate
There are four types of chemical reactions: synthesis, combustion, decomposition, and replacement reactions.
Section 9-2

15. Types of Chemical Reactions
Chemists classify reactions in order to organize the many types.
Why do this?
Help predict products before a reaction happens. (Table 9.4 in book)
A ________________or_________________ is a reaction in which two or more substances react to produce a single product.
Section 9-2

16. Types of Chemical Reactions (cont.)
When two elements react, the reaction is always a synthesis reaction.
Section 9-2

17. Types of Chemical Reactions
A __________________________is one in which a single compound breaks down into two or more elements or new compounds.
Decomposition reactions often require an energy source, such as heat, light, or electricity, to occur.
H2O → H2 + O2
Section 9-2

18. Types of Chemical Reactions (cont.)
In a ______________________oxygen combines with a hydrocarbon (made mostly of C and H) and releases carbon dioxide, water, heat, and light.
CH4 + O2 → CO2 + H2O
Section 9-2

19. Types of Chemical Reactions
A reaction in which the atoms of one element replace the atoms of another element in a compound is called a _____________________________
A + BX → AX + B
“The Player at the Prom”
Section 9-2

20. Replacement Reactions (cont.)
_______________________occur when ions exchange between two compounds.
“The Perfect Prom”
Section 9-2

21. Replacement Reactions (cont.)
The solid product produced during a chemical reaction in a solution is called a ______________________.
All double replacement reactions produce either water, a precipitate, or a gas.
Section 9-2

22. A B C D 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 B C D
Section 9-2

23. A B C D Section 9.2 Assessment
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 A B C D
Section 9-2

24. Section 9.3 Reactions in Aqueous Solutions
Describe aqueous solutions.
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.
solution: a uniform mixture that might contain solids, liquids, or gases
Section 9-3

25. Section 9.3 Reactions in Aqueous Solutions (cont.)
solute
solvent
complete ionic equation
spectator ion
net ionic equation
Double-replacement reactions occur between substances in aqueous solutions and produce precipitates, water, or gases.
Section 9-3

26. The solvent is the most plentiful substance in a solution.
Aqueous Solutions
An ________________________contains one or more dissolved substances (called solutes) in water.
The solvent is the most plentiful substance in a solution.
Section 9-3

27. Aqueous Solutions (cont.)
Water is always the solvent in aqueous solutions.
There are many possible solutes:
ie: sugar, alcohol
Compounds that produce hydrogen ions in aqueous solutions are acids.
Ionic compounds can also be solutes in aqueous solutions.
When ionic compounds dissolve in water, their ions separate in a process called dissociation.
Gatorade and electrolytes !!!
Section 9-3

28. 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 ____________________________ reaction.
Three products can form:
precipitates,
water, or
gases.
Section 9-3