Science 10Science 10
Investigating Chemical Reactions!Investigating Chemical Reactions!
Chemical ReactionsChemical Reactions
Magnesium (Mg) and Oxygen (OMagnesium (Mg) and Oxygen (O22))Before Burning: Before Burning:
Mg: silver colour, lightweight, metal.Mg: silver colour, lightweight, metal.OO22: invisible gas in air.: invisible gas in air.
After burning: white powder.After burning: white powder.
Chemical ReactionsChemical Reactions
A A chemical reactionchemical reaction is is the process that leads to the process that leads to a chemical change in a chemical change in which which new substancesnew substances with with new propertiesnew properties are are formed.formed.
They can be summarized They can be summarized 2 ways…2 ways…
Chemical ReactionsChemical Reactions
1. As a word equation1. As a word equation i.e.: magnesium plus oxygen react to produce i.e.: magnesium plus oxygen react to produce
magnesium oxide.magnesium oxide.Or a generic equation: Or a generic equation:
reactant(s) yield(s) product(s)reactant(s) yield(s) product(s)2. As an equation using formulas:2. As an equation using formulas:
i.e.: i.e.: Mg + OMg + O22 → MgO → MgO
Antoine LavoisierAntoine Lavoisier Who?: Who?:
French Nobleman (aristocracy)French Nobleman (aristocracy) Wealthy familyWealthy family Tax collector before the French Tax collector before the French
RevolutionRevolution Beheaded during the Revolution Beheaded during the Revolution
(1794) during the Reign of (1794) during the Reign of Terror.Terror.
When?:When?: Late 1700’s, during the French Late 1700’s, during the French
Revolution Revolution Where?: Where?:
FranceFrance
Antoine LavoisierAntoine Lavoisier
Discoveries he made:Discoveries he made:1. Named oxygen and 1. Named oxygen and
hydrogen as elements.hydrogen as elements.2. Helped develop the 2. Helped develop the
metric system.metric system.3. Developed the “3. Developed the “Law of Law of
Conservation of MassConservation of Mass”.”.
The Law of Conservation of MassThe Law of Conservation of Mass
In any chemical reaction the total mass In any chemical reaction the total mass of the reactants will always equal the of the reactants will always equal the total mass of the products.total mass of the products. (As long as (As long as the reaction is the reaction is closedclosed))What goes in, must come out!What goes in, must come out!
Mass is neither lost nor gained in a chemical reaction!!!
The Law of Conservation of AtomsThe Law of Conservation of Atoms
In any chemical reaction, atoms are In any chemical reaction, atoms are neither created nor destroyed.neither created nor destroyed.
So…Mg + So…Mg + OO22 → Mg → MgOO is not a balanced is not a balanced
reaction.reaction.
AssignmentAssignment
C.Y.U. 9.1 p. 234.C.Y.U. 9.1 p. 234.# 1,2,5,6,8,9 in point form.# 1,2,5,6,8,9 in point form.# 4 & 7 in complete sentences.# 4 & 7 in complete sentences.
Balancing Chemical EquationsBalancing Chemical Equations
Let’s combine Let’s combine sodiumsodium and and chlorinechlorine in a in a chemical equation:chemical equation:Na + ClNa + Cl22 → NaCl → NaCl Reactants yield productsReactants yield productsThis is a skeleton equation; correct formula, This is a skeleton equation; correct formula,
but it is not balanced.but it is not balanced.
Note: chlorine is a Note: chlorine is a diatomic diatomic element. What are the other element. What are the other diatomic elements?diatomic elements?
-Cl-Cl22, H, H22, N, N22, O, O22, F, F22, Br, Br22, I, I22
Balancing Chemical EquationsBalancing Chemical Equations
All chemical equations must obey 2 laws All chemical equations must obey 2 laws of basic chemistry:of basic chemistry:The law of conservation ofThe law of conservation of atomsatoms
In any chemical reactions, atoms are neither In any chemical reactions, atoms are neither created nor destroyed.created nor destroyed.
The law of conservation of massThe law of conservation of massIn any chemical reaction, the mass of the reactants In any chemical reaction, the mass of the reactants
always equals the mass of the products,always equals the mass of the products,
Balancing Chemical EquationsBalancing Chemical Equations
Let’s balance the equation:Let’s balance the equation:Na + ClNa + Cl22 → NaCl → NaCl
The balanced equation must have the same The balanced equation must have the same number of Na and Cl on each side:number of Na and Cl on each side:22Na + ClNa + Cl22 → → 22NaClNaCl
Let’s see how this is done…
Balancing Chemical EquationsBalancing Chemical Equations
1. Cu2S + O2 → Cu2O + SO2 How many Cu atoms are in the reactants? ___ in the products?___ What coefficient(s) will make the number of Cu
atoms in the reactants and products equal?___ How many S atoms are in the reactants?___ in the products?___ What coefficient(s) will make the number of S
atoms in the reactants and products equal?___
Balancing Chemical EquationsBalancing Chemical Equations
Cu2S + O2 → Cu2O + SO2 How many O atoms are in the reactants? in the
products?___ What coefficient(s) will make the number of O atoms in
the reactants and products equal?___ Do any coefficients need to be changed? ___
Rewrite the equation and balance:
2Cu2S + 3O2 → 2Cu2O + 2SO2
Balancing Chemical EquationsBalancing Chemical Equations
So when balancing a chemical equation So when balancing a chemical equation ask yourself:ask yourself:How many atoms of each element are in the How many atoms of each element are in the
reactants?reactants?How many atoms of each element are in the How many atoms of each element are in the
products?products?What coefficients do I need to make the What coefficients do I need to make the
equal? equal? You might need to use lowest common multiples to You might need to use lowest common multiples to
figure it out.figure it out.You might need to add coefficients to elements You might need to add coefficients to elements
that started out equal.that started out equal.
Balancing Chemical EquationsBalancing Chemical Equations
Balancing Chemical EquationsBalancing Chemical Equations
Balancing Chemical EquationsBalancing Chemical Equations
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