5. Give the physical state of each of
these:
1. Silver Solid
2. Gasoline Liquid
3. Helium Gas
4. Rubbing alcohol Liquid
5. Air Gas
6. Glass Solid or liquid
7. Lightning Plasma
10. Chemical or physical change ???
• Food spoiling Chemical
• Nail rusting Chemical
• Oil burning Chemical
• Sugar dissolving Physical
• Water boiling Physical
• Firefly flashing Chemical
• Egg cooking Chemical
• Snowflake melting Physical
12. Calculations
1. A 78.0 g sample of an unknown
compound contains 12.4 g of
hydrogen. What is the percent by mass
of hydrogen in the compound?
2. If 1.0 g of hydrogen reacts completely
with 19.0 g of fluorine, what is the
percent by mass of hydrogen in the
compound that is formed?
13. Pure Substances
• Elements are the building blocks of
matter.
• Atoms are the smallest part of an
element.
14. Mixtures
… do not have a definite
composition
… are either heterogeneous,
with clearly visible components
… or homogeneous,
which are uniform in
appearance
27. Part of the Atom
• Electron
• Proton
What charge does each have?
• Neutron
Where are they found?
Which ones make up the mass of the
atom?
Which ones make up the size of the
atom?
28. How Do Atoms Differ?
•Atomic Number
•Atomic Mass
29. Element Atomic Protons Electrons Atomic
Number Mass
He 2
Pb 82
8
30
31. Isotopes …
…of the same element have the
same number of protons and
electrons but different numbers of
neutrons.
Therefore, isotopes of the same
element have different masses.
32. Symbols for Isotopes
Mass number
A is the
A Symbol
E
symbol
for mass Z of
Element
number
Z is the symbol for
Atomic
number
atomic number
40. Electromagnetic
Spectrum
• Electromagnetic waves
carry energy.
• Light is part of the
electromagnetic spectrum
41. The Electromagnetic Spectrum
gamma rays
microwaves
visible light
ultraviolet
infrared
X-rays
radar
radio
TV
Shorter wavelength Longer wavelength
Higher frequency Lower frequency
Higher energy Lower energy
42. gamma rays
X-rays
400 nm
ultraviolet
visible light
infrared
microwaves
Increasing energy
radar
TV
700 nm
radio
The Electromagnetic Spectrum
43. The visible spectrum was
discovered by …
Dr. Roy G. Biv
Red Orange Yellow Green Blue Indigo Violet
700 nm 400 nm
Lower energy Higher energy
44. Niels Bohr
Bohr said that electrons could exist only
in certain discrete energy levels …
… and that electrons can only change
energy levels when they absorb or give
off a certain amount of energy. (1913)
45. Hydrogen
atom
Discrete energy levels for electrons
electron nucleus
46. Hydrogen
atom
Electrons can exist in this orbit,
50. Hydrogen
atom
Unless the electron is
absorbing energy, or …
Giving off energy
51. When high voltage is connected to
the hydrogen discharge tube, a
bluish light is given off.
When observed through a
diffraction grating, specific lines
of color are observed.
52. The electron in a hydrogen
atom gains energy from the
electricity passing thru the
tube and …
… the electron moves up to a
higher energy level.
53. The electron in the excited
state is “unstable”.
The electron drops to a lower
energy level, and …
… gives off light of a certain
energy and wavelength.
62. “Regardless of it’s
shortcomings and the
modifications that were later
applied, Bohr’s model of the
atom was the first
successful attempt to make
the internal structure of the
atom agree with
spectroscopic data.”
Asimov, 1964
63. Quantum
Mechanical Model of
the Atom
1. A small, dense positively
charged nucleus which
contains protons and neutrons.
2. Electrons which exist outside of
the nucleus at …
– various distances from the nucleus,
and at …
– various energy levels.
64. The Electrons
3. The electrons can have both a mass,
as does matter, and a wavelength,
as does light energy.
4. The electrons themselves are not
little solid spheres in orbit around the
nucleus, but exist as a “fog” of half-
energy, half-matter. The electrons
can behave as either matter or
energy, depending on the
experiment.
65. Energy Levels
5. Based on the ideas of Bohr, the
electrons are located …
– … in major energy levels,
– … in energy sublevels within major
energy levels,
– … in orbitals within each sublevel.
Substance – matter that has uniform and unchanging composition (pure substance) – table salt, water, sea water Physical properties – observed and measured without changing the composition – density, color, odor, taste, hardness, melting point, boiling point Chemical Properties – Ability of a substance to combine with or change into one or more other substances – iron rust, reactions.
Solute can differ. Solvent is usually water.
Table salt, water, sugar, aspirin. 10 million known compounds. Medicines.
Distinctly different properties – water and peroxide
Atomic Number – number of protons in an atom. On top. Atomic Mass – number on bottom.