Why is Chemistry Important to You?

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Why is Chemistry Important to You?

• knowledgechemistry is everywhere!
• college acceptance/scholarships
• required for most science, technical, industrial,
  and medical careers
• many career opportunities
• earning potential (mid-career Chemical Engineer
  w/BA makes 108,000 on average)
• national security, economics

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Lab Safety

• Read GENERAL RULES
• Answer Questions 56-58
• AGREEMENT form You and your parent or guardian
  must sign before you can perform lab activities.
• You must pass SAFETY TEST before you can perform
  lab activities.

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Ch. 1, 2, and 4 Matter and Atomic Structure
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Objectives

• Be familiar with terminology related to different
  classifications of matter.
• Be able to classify examples of matter into
  appropriate categories.
• Understand the difference between physical
  changes and chemical changes.

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Classifying Matter
MATTER
substance single composition
mixture a blend of substances amounts vary
element simplest substance has only one kind
of atom represented by a symbol C, Fe, U
compound has two or more elements in a specific
ratio represented by a formula NaCl, C12H22O11
homogeneous mixture a uniform blend of
substances air, salt water, steel, gasoline
heterogeneous mixture a non-uniform blend,
different parts are visible granite, sand, soup,
snow
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Matter and Change

• physical property a characteristic used to
  identify a substance
• physical change same substance before/after
  (boiling, grinding, etc.)
• chemical change different substances produced
  (burning, rusting, etc.)

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Objectives

• Understand historical developments regarding the
  concept of the atom.
• Be able to discuss atomic theory.
• Be able to conceptualize the very small size of
  atoms.

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Atoms (Atomos)

• Democritus, Greek philosopher (500 BC) matter
  is composed of small, indivisible particles
• atomos indivisible)

9
John Dalton

• John Dalton had first experimental evidence that
  atoms exist (1803).
• Two types of tin oxide stannous oxide and
  stannic oxide.
• stannic oxide has exactly 2X more oxygenwhy?
• simple explanation stannic oxide must have twice
  as many oxygen atoms

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Daltons Atomic Theory (1803)

• All matter is composed of indivisible atoms.
• Each element has unique, identical atoms.
• Atoms combine in whole-number
  ratios to make compounds.
• Atoms rearrange in reactions.
• (not totally true)

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Atomic Size

• Seen with an electron microscope.
• Measured in picometers (1 pm 10-12 m).
• 100 million copper atoms in a row 1 cm

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Objectives

• Know the characteristics of the types of
  subatomic particles.
• Be familiar with experiments that revealed the
  structure of the atom.

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Subatomic Particles Within Atoms
particle symbol relative charge relative mass (u) actual mass (kg) year of discovery
electron e- 1- 1/1840 9.11x10-31 1897
proton p 1 1 1.67x10-27 1919
neutron no 0 1 1.67x10-27 1932
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Plum-Pudding Model

• J.J. Thomson discovered electrons in 1897
• plum-pudding atomic model electrons are
  distributed in a sphere of positive charge.

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Rutherfords Gold Foil Experiment1911
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The Nucleus

• hypothesis all particles will pass through the
  foil
• result 1/10000 are deflected
• conclusion atoms have a dense, positive
  nucleus 1/10000 the diameter of the atom

expected result
actual result
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Atomic Structure

• nucleus contains p and no
• e- orbit the nucleus
• Why dont p fly apart?
• nuclear strong force at very short distances,
  nuclear particles (no and p) attract each other,
  gluing nucleus together

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Objectives

• Understand the meaning of atomic number and mass
  number.
• Understand the concept of isotopes and be able to
  represent isotopes with appropriate names and/or
  symbols.

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Atomic Number

• atomic number number of p in nucleus
• each element has different atomic
• () charge in nucleus atomic
• atoms are neutral because p e-
• The number of no varies within an element.
• isotope atoms of the same element (same atomic
  ), but have a different of no

12
Mg
24.305
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Isotope Names and Symbols

• oxygen has 3 isotopes oxygen-16, oxygen-17, and
  oxygen-18
• mass number sum of p and no in nucleus
• of no mass - atomic

mass
atomic
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Atomic Mass Unit

• atomic mass unit (amu or just u) unit used to
  measure the mass of atoms
• 1.00 u exactly 1/12 the mass of a carbon-12
  atom
• carbon-12 12.000 u
• p 1.007276 u 1 u
• no 1.00866 u 1 u
• e- 0.0005486 u 0 u

Interesting fact if you add the mass of 6p ,
6no, and 6e-, the sum equals12.09891u. But when
combined in an atom, the mass equals exactly
12.000u. The missing mass is converted into the
binding energy that holds the atom together
(Emc2).
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Objectives

• Understand the concept of atomic mass.
• Be able to calculate atomic mass when given
  isotope mass data.

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Atomic Mass

• atomic mass weighted average mass of all
  isotopes in an element (the average mass of an
  atom)
• example chlorine has two isotopes
• 75.77 is chlorine-35 34.969 u
• 24.23 is chlorine-37 36.966 u
• (34.969 x 0.7577) (36.966 x 0.2423) 35.4529
  u
• No single chlorine atom has this mass, but it is
  the average atomic mass that we use.
• An elements most common isotope can often be
  found by rounding off its atomic mass.

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Groups and Periods
group vertical column elements have similar
properties
period horizontal row properties vary greatly
group
period