Chemistry 12 Mr Chumbley Section 1 Describing Chemical Reactions Chemical Reactions A chemical reaction is a process by which one or more substances change to produce one or more different substances ID: 920980
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Slide1
Chapter 8: Chemical Equations and Reactions
Chemistry 1-2
Mr.
Chumbley
Slide2Section 1: Describing Chemical Reactions
Slide3Chemical Reactions
A
chemical reaction
is a process by which one or more substances change to produce one or more different substances
A
chemical equation is a representation of a chemical reaction that uses symbols to show the relationship between the reactants and products
Slide4Indicators of a Chemical Reaction
While absolute proof of a chemical change can only be found through chemical analysis, there are certain indicators a chemical reaction has occurred
Release of energy as heat and light
Color change
Production of a gas
Formation of a precipitateA precipitate is a solid that is produced as a result of a chemical reaction in a solution
Slide5Chemical Equations
Chemical equations must satisfy certain criteria:
The equation must represent all known facts
The equation must contain the correct formulas for the reactants and the products
The law of conservation of mass must be satisfied
A coefficient is a small whole number that appears in front of a formula in a chemical equation
Slide6Word Equations
A
word equation
is an equation in which the reactants and products in a chemical reaction are represented with words
An arrow in an equation is read as “reacts to yield” or “yields”
The above equation would be read as:Methane and oxygen react to yield carbon dioxide and water
Slide7Formula Equations
A
formula equation
represents the reactants and products of a chemical reaction by their symbols and formulas
The reaction would be read the same as in the word equation:
Methane and oxygen react to yield carbon dioxide and waterNeither the word equation nor the formula equation give information about the amounts of reactants or products
Slide8Symbols Used in Chemical Equations
“yields”; indicates
a reaction
indicates a reversible reaction
(
s)solid state↓precipitate formed as product(l)liquid state(aq)in aqueous solution(g)gas state↑
gas formed
as product
reaction
requires heat
specific
temperature at which reaction was carried out
reaction requires pressure
specific
pressure at which reaction was carried out
catalyst
used to alter reaction rate
“yields”; indicates
a reaction
indicates a reversible reaction
(s)solid state↓precipitate formed as product(l)liquid state(aq)in aqueous solution(g)gas state↑gas formed as productreaction requires heatspecific temperature at which reaction was carried outreaction requires pressurespecific pressure at which reaction was carried outcatalyst used to alter reaction rate
Slide9Diatomic Elements
Some elements do not exist as individual atoms in nature.
These non-metals are found in elemental form as two atoms bonded together
Element
Molecular Formula
State of MatterHydrogenH2GasNitrogenN2GasOxygenO2GasFluorineF2GasChlorineCl2GasBromineBr2LiquidIodineI2
Liquid
Slide10Sample Problem A
Write word and formula equations for the chemical reaction that occurs when solid sodium oxide is added to water at room temperature and forms sodium hydroxide (dissolved in water)
Slide11Homework!
Practice A (p. 254)
Slide12Balanced Equations
While a formula equations describe the formulas in a reaction, they don’t necessarily describe the correct amounts
A balanced equation has all of the chemical formulas in the correct ratios to fully satisfy the law of conservation of mass
Slide13Balancing Equations
Slide14Balancing Equations
Lithium metal and aluminum sulfate solution react to yield a lithium sulfate solution and aluminum metal.
Slide15Section 2: Types of Chemical Reactions
Slide16Synthesis Reaction
In a
synthesis reaction
two or more substances combine to form a new compound
Slide17Decomposition Reaction
In a
decomposition reaction
a single compound breaks down into two or more simpler substances
Slide18Single Displacement Reaction
In a
single displacement
one element replaces a similar element in a compound
Slide19Double Displacement Reaction
In a
double displacement
the ions of two compounds exchange places in an aqueous solution to form two new compounds
Slide20Combustion Reaction
A
combustion reaction
is the oxidation reaction of an element or compound in which energy as heat is released