a chemical change must occur as it is the result of a chemical reaction. a reaction could include...
TRANSCRIPT
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Chemical Reactions
In chemistry, a reaction occurs when two or more substances interact and
something happens.
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KEY POINTS
A chemical change must occur as it is the result of a chemical reaction.
A reaction could include ions, molecules, or pure atoms (elements).
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Energy of Chemical Reactions
Endothermic Exothermic
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Endothermic
Energy – absorbed Required for reaction Absorbed energy - often
heat or electrical energy.
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Exothermic
Energy - released Released energy - originally stored
in bonds of reactants Often heat given off causes
product(s) to feel hot. Reactions involving combustion or
burning are exothermic chemical reaction.
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REACTION TYPES
SYNTHESIS (Combination) DECOMPOSITION SINGLE REPLACEMENT
(Displacement) DOUBLE REPLACEMENT
(Double Displacement) COMBUSTION
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Synthesis
Two or more reactants yielding one product is a way to identify a synthesis reaction.
Generic Example:
A + B ABH2 + O H2O
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Synthesis Example
Simple hydrogen gas combined with simple oxygen gas can produce a more complex substance --- water!
S + O2 SO2reactant + reactant -------> product
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Decomposition
A more complex substance (reactant) breaks down into its more simple parts (products).
AB A + B Synthesis and decomposition
reactions are opposites. catalyst – a substance that causes or
accelerates a chemical reaction without itself being affected.
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Decomposition Example
Water can be broken down into hydrogen gas and oxygen gas.
2H2O 2H2
+ O2reactant -------> product + product
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Single Replacement
In a single replacement reaction a single uncombined element replaces another in a compound. Two reactants yield two products.
A + BC AC + B Mg + 2AgNO3 Mg(NO3)2
+ 2Ag
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Single Replacement Example
When zinc combines with hydrochloric acid, the zinc replaces hydrogen.
Zn + 2HCl ZnCl2 + H2
reactant + reactant ------> product + product
Demonstration Time!
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Double Replacement
In a double replacement reaction parts of two compounds switch places to form two new compounds. Two reactants yield two products.
AB + CD AD + CBprecipitate - to separate (a substance)
in solid form from a solution, as by means of a chemical reaction.
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Double Replacement Example
When silver nitrate combines with sodium chloride, two new compounds are formed --silver chloride and sodium nitrate -- because the sodium and silver switched places.
AgNO3 + NaCl AgCl + NaNO3
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Combustion
Combustion reactions always involve molecular oxygen O2.
Anytime anything burns (in the usual sense), it is a combustion reaction.
Combustion reactions are almost always exothermic (i.e., they give off heat).
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Works Cited
Howcast. " YouTube - Balancing Chemical Equations - H2O ." YouTube - Broadcast Yourself. . N.p., n.d. Web. 5 Mar. 2011. <http://www.youtube.com/watch?v=jdUQzVMB4Hw&feature=player_embedded>.
"Types of Chemical Reactions." Utah State Office of Education - USOE - Welcome. N.p., n.d. Web. 5 Mar. 2011. <http://schools.utah.gov/curr/science/sciber00/8th/matter/sciber/chemtype.htm>.
brightstorm2. " YouTube - Decomposition Reaction ." YouTube - Broadcast Yourself. . N.p., n.d. Web. 5 Mar. 2011. <http://www.youtube.com/watch?v=yuStJotow2I>.
"chemical reactions:combustion." Indiana University Northwest. N.p., n.d. Web. 5 Mar. 2011. <http://www.iun.edu/~cpanhd/C101webnotes/chemical%20reactions/combustion.html>.
ochem9. " YouTube - Five Major Chemical Reactions ." YouTube - Broadcast Yourself. . N.p., n.d. Web. 5 Mar. 2011. <http://www.youtube.com/watch?v=tE4668aarck>.
tszheichoi. " YouTube - Hygrogen and oxygen from water ." YouTube - Broadcast Yourself. . N.p., n.d. Web. 5 Mar. 2011. <http://www.youtube.com/watch?v=OTEX38bQ-2w&feature=related>.
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