l01 matter & balancing equations
DESCRIPTION
chemistryTRANSCRIPT
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MATTER
Dr S. Lawrence
Kane Room 2.04B
Chemistry: The Central Science
Sections 1.1, 1.2 and 1.3 (12th Edition)
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CLASSIFICATION OF MATTER
ATOM - the smallest unit of matter (H, Fe, Cl, Zn, C, O, etc.)
(made up of neutrons, protons and electrons)
MOLECULE - two or more atoms bound together
by chemical bonding (O2, NaCl, H2O, C6H12O6)
ELEMENT a collection of atoms of one atom type (H2, S8, He, Cl2, Fen)
COMPOUND collections of different atom types (H2O, FeCl3, CO2)
MIXTURE collections of more than one atom or molecules (H2O + CO2 + C6H12O6)
PURE SUBSTANCE collections of one identical molecule/atom (H2O, S8)
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ATOMS
OF AN ELEMENT
e.g. He
MOLECULES
OF AN ELEMENT
e.g. H2
MOLECULES
OF A COMPOUND
e.g. BF3
MIXTURE
OF ELEMENTS
AND A COMPOUND
CLASSIFICATION OF MATTER
USING MODELS
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H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Only one type of atoms.
ELEMENTS
Different elements have atoms containing different numbers
of protons (in the neutral atom).
Listed in the Periodic Table of Elements.
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Molecules are groups of atoms joined together by chemical bonds.
either shared by the atoms
Chemical bonds: attractive forces involving electrons
MOLECULES
or transferred to create ions of opposite charge.
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PROPERTIES OF MATTER
Every substance has a unique set of properties
determined by the atoms present in the molecules
Physical - colour, density, melting point, boiling point
Chemical - the way the substance may react to form
other substances (flammability)
MATTER can be converted to ENERGY and vice versa
Einstein equation: E = mc2
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PHYSICAL CHANGES AND PROPERTIES
Steam Water Ice Heating Heating
Cooling Cooling
Substances change their physical state, but not composition.
Mixtures form from, or can be separated into, their components.
GAS LIQUID SOLID
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Reactants form products
CHEMICAL CHANGES
Atoms combine, but are neither created nor destroyed.
Chemical energy may be released as heat - thermodynamics.
Heating may also accelerate a chemical reaction - kinetics.
A chemical change is when new molecules are formed by
reaction of other atoms or molecules.
2 H2O + Energy 2 H2 + O2
Combustion
Called a chemical reaction
Described by a chemical equation: indicates the numbers
of atoms/molecules involved in the reaction.
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BALANCING EQUATIONS
Chemistry the Central Science: 3.1 (12th Edition)
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Chemical
Symbol
Meaning Composition
H2O One molecule of water Two atoms of hydrogen and one
atom of oxygen
2H2O Two molecules of water Four atoms of hydrogen and
two atoms of oxygen
H2O2 One molecule of
hydrogen peroxide
Two atoms of hydrogen and two
atoms of oxygen
Chemical Symbols
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Thoughts for Balancing Equations
4 Deal first with elements which occur in the fewest
formulae.
1 Chemical symbols stay the same,
i.e. cannot change subscripts.
H2O is water H2O2 is hydrogen peroxide
2 The ONLY thing you can do is to put numbers in
front of formulae.
3 Before you start, count each element it may already be balanced! (it does happen.)
Can change H2O to 2H2O
Balanced No. of Reactants = No. of Products
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BALANCING CHEMICAL EQUATIONS - Combustion
CO2 + H2O C2H5OH + O2
1. Write the unbalanced chemical equation
2 CO2 + H2O C2H5OH + O2
2. Balance the carbons first
3. Balance the hydrogen
2 CO2 + 3 H2O C2H5OH + O2
4. Finally, balance oxygen
2 CO2 + 3 H2O C2H5OH + 3 O2
5. Check the sums of atoms
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CO2 + H2O CH3OH + O2
1. Write the unbalanced chemical equation
CO2 + H2O CH3OH + O2
2. Balance the carbons first
3. Balance the hydrogen
CO2 + 2 H2O CH3OH + O2
4. Balance the oxygen
CO2 + 2 H2O CH3OH + 3/2 O2
5. Multiply the equation by 2 to get whole numbers
2 CO2 + 4 H2O 2 CH3OH + 3 O2
EXAMPLE: Combustion of methanol
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1 C + O2 CO2 2 C + O2 CO 3 S8 + O2 SO2 4 P4 + Cl2 PCl3