2. Introduction to ChemicalIntroduction to Chemical
ReactionsReactions
SUBMITTED BYSUBMITTED BY
V ISHNU.S.PILLAIV ISHNU.S.PILLAI
PHYSICAL SCIENCEPHYSICAL SCIENCE
3. Main IdeasMain Ideas
Chemical Reactions are represented byChemical Reactions are represented by
Chemical Equations.Chemical Equations.
Chemical Equations are balanced toChemical Equations are balanced to
show the same number of atoms of eachshow the same number of atoms of each
element on each side.element on each side.
6. Representing ChemicalRepresenting Chemical
ReactionsReactions
Chemists observe chemical reactions and have comeChemists observe chemical reactions and have come
up with a way to represent or model what isup with a way to represent or model what is
happening.happening.
Making NaClMaking NaCl
Solid Sodium combines with Chlorine gas to makeSolid Sodium combines with Chlorine gas to make
solid Sodium Chloride:solid Sodium Chloride:
2Na (s) + Cl2 (g)2Na (s) + Cl2 (g) 2NaCl2NaCl
7. Chemical Equations are differentChemical Equations are different
from Numerical Equationsfrom Numerical Equations
Numerical Equation: 3x + 2y = 47Numerical Equation: 3x + 2y = 47
Chemical Equation 2Na + Cl2Chemical Equation 2Na + Cl2 2NaCl2NaCl
ReactantA + Reactant BReactantA + Reactant B ProductProduct
The reactants are used up in forming the productThe reactants are used up in forming the product
The arrowThe arrow shows the direction of the reactionshows the direction of the reaction
8. Symbols used inSymbols used in
Chemical EquationsChemical Equations
Symbol Purpose
+ Separates more than one reactant or
product
Separates reactants from products.
Indicates direction of reaction
(s) Identifies a solid state
(aq) Identifies that something is dissolved
in water
(l) Identifies liquid state
(g) Identifies gaseous state
9. Balancing EquationsBalancing Equations
After you write a chemical equation you have to balance it toAfter you write a chemical equation you have to balance it to
make sure that the same number of atoms of each elementmake sure that the same number of atoms of each element
are on each side.are on each side.
How would you balance this equation?How would you balance this equation?
Li + H2OLi + H2O H2 + LiOHH2 + LiOH
10. Steps to Balancing a Chemical EquationSteps to Balancing a Chemical Equation
11. Example ContinuedExample Continued
Change the Coefficients to make the number ofChange the Coefficients to make the number of
atoms of each element equalatoms of each element equal
Balance the Hydrogens:Balance the Hydrogens:
CH4 + O2CH4 + O2 CO2 +CO2 + 22 H2OH2O
Balance the Oxygens:Balance the Oxygens:
CH4 +CH4 + 22 O2O2 CO2CO2 ++ 22 H2OH2O
