iiiiiiivv ch. 8 – chemical equations & reactions
TRANSCRIPT
I II III IV V
Ch. 8 – Chemical Equations & Reactions
Describing Chemical Reactions
Process by which one or more substances are changed into one or more different substances
Chemical equation- represents with symbols & formulas identities and amounts of reactants and products
All Chemical Reactions
have two parts Reactants - the substances you start
with Products- the substances you end up
with The reactants turn into the products. Reactants Products
Chemical Equations
A+B C+DREACTANTS PRODUCTS
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Visual Concept
Chemical Equation
C. Johannesson
Law of Conservation of Mass mass is neither created nor destroyed
in a chemical reaction
4 H
2 O
4 H
2 O4 g 32 g
36 g
total mass stays the same atoms can only rearrange
Signs of a Chemical Reaction Creation of heat and
light Formation of a gas Formation of a
precipitate – solid produced and separated from a solution
Color change
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Visual Concept
Signs of a Chemical Reaction
Characteristics of Chemical Equations, continuedAdditional Symbols Used in Chemical Equations
Section 1 Describing Chemical ReactionsChapter 8
Characteristics of Chemical Equations, continuedAdditional Symbols Used in Chemical Equations
Section 1 Describing Chemical ReactionsChapter 8
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Visual Concept
Symbols Used in Chemical Equations
Writing Equations
Identify the substances involved. Use symbols to show:
2H2H22((gg) + O) + O22((gg) ) 2H 2H22O(O(gg))
How many? - coefficient
Of what? - chemical formula
In what state? - physical state
Describing Equations Describing Coefficients:
individual atom = “atom”
covalent substance = “molecule”
ionic substance = “unit”
3 molecules/MOLES of carbon dioxide
2 atoms/MOLES of magnesium
4 units/MOLES of magnesium oxide
3CO2
2Mg
4MgO
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Visual Concept
Interpreting Chemical Equations
DAY 3
Ch. 8 – Chemical Equations & Reactions
Synthesis
the combination of 2 or more substances to form a compound
only one product
A + B AB
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Visual Concept
Synthesis Reactions
Decomposition
a compound breaks down into 2 or more simpler substances
only one reactant
AB A + B
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Visual Concept
Electrolysis
C. Johannesson
Single Replacement
one element replaces another in a compound Reactants must be an element and a compound.
metal replaces metal (+) nonmetal replaces nonmetal (-)
A + BC B + AC
C. Johannesson
AB + CD AD + CB
Double Replacement
Two things replace each other. Reactants must be two ionic compounds or acids. ions in two compounds “change partners”
cation of one compound combines with anion of the other
Pb(NO3)2(aq)+ KI(aq) PbI2(s)+ KNO3(aq)
E. Double Replacement
Products: switch negative ions one product must be insoluble
NaNO3(aq)+ KI(aq) N.R.
2 2
Types of Reactions: Combustion
CH4(g) + 2O2(g) CO2(g) + 2H2O(g)
the burning of any substance in O2 to produce heat
A + O2 B
Na(s)+ O2(g)
C3H8(g)+ O2(g) 5 3 4
Combustion
Products: contain oxygen hydrocarbons form CO2 + H2O
CO2(g)+ H2O(g)
Na2O(s) 4 2
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Visual Concept
Combustion Reaction
DAY 4
Ch. 8 – Chemical Equations & Reactions
B. Exothermic Reaction
reaction thatreleases energy
products have lower PE than reactants
2H2(l) + O2(l) 2H2O(g) + energy
energyreleased
C. Endothermic Reaction
reaction that absorbs energy
reactants have lower PE than products
2Al2O3 + energy 4Al + 3O2
energyabsorbed
Activity Series
Activity- ability of an element to react Activity Series- list of elements
organized according to the ease with which they undergo certain reactions Metals greater activity greater ease
of loss of electrons (cations) Nonmetals greater activity greater
ease of gain of electrons (anions)
Activity Series of the Elements
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Visual Concept
Activity Series