Transcript Chemistry Comes Alive

Chemistry—An
Introduction
Chapter 2
Pages 25-33
Matter
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Occupies space and has mass
Mass is NOT the same as weight
States of matter
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Solid
Liquid
Gaseous
Energy
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Can only be measured by effect on
matter
Defined as:
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The capacity to do work
Two types
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Kinetic energy
Potential energy
Forms of Energy
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Chemical energy
Electrical energy
Mechanical energy
Electromagnetic energy
All forms are easily convertible
Elements and Atoms
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All matter composed of elements
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Elements composed of atoms
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Cannot be broken down
Ex: Oxygen, Carbon, Gold, Silver, Copper, Iron
Unique in each element
Atomic symbol
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Abbrev. for element
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O = Oxygen, C = Carbon
Atomic Structure
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Atoms contain smaller structures
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Nucleus
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Electrons (e-)
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Most dense and most of mass of atom (1amu)
Neutrons (n0)
Protons (p+)
Tiny, 1/2000 mass of protons and neutrons
Equal number of protons and electrons
Identifying Elements
Atomic Number
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= to number of protons in a nucleus
Written as subscript to Left of atomic
symbol
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Ex: (1H); (2He)
Mass Number
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= to sum of masses of protons + neutrons
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Written as superscript to Left of atomic
symbol
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Ex: H mass number = 1(p+) + 0 (n0) = 1
He mass number = 2 (p+) + 2 (n0) = 4
Now know total numbers of all subatomic particles
Structural variations
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Called isotopes
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Differ in number of neutrons
Atomic Weight
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Avg of mass numbers of all isotopes of
an element
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Also takes into account relative abundance
Ex: H atomic wt. = 1.008
Molecules and Compounds
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Molecule
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Two or more atoms held together by a
chemical bond
Compound
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Two or more different atoms held together
by a chemical bond
Chemically pure
Mixtures
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Composed of two or more substances
that are physically mixed
Three types:
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Solutions
Colloids
Suspensions
Solutions
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Homogeneous mixtures
Solvent
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Substances present in greater amt
Solute
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Present in smaller amts
Concentration of Solutions
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Described in terms of % of the solute in
solution
Can also describe in terms of molarity (moles
per liter) (M)
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Mole = to molecular weight
Avogadro’s number = 6.02 x 1023
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Makes sure that the substance always contains
exactly same number of solute particles
Colloids
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Heterogeneous mixtures
Appear milky
Ex: Jello-O, cytosol
Suspensions
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Heterogeneous mixtures
Contain lg solutes that settle out
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Ex: Sand and water
Ex: Blood
Mixtures vs. Compounds
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No chemical bonding occurs between
components of a mixture
Mixtures can be separated by physical
means; compounds cannot
Mixtures can be hetero- or
homogeneous; compounds are only
homogenous