Download Science - Byron High School

Some slides adapted from Burlingame HS
the systematic investigation of
nature
 neither
 it depends on how it is used (based on
your values)
 to make intelligent decisions one must
know the facts & consider the risks and
benefits.
 the study of the composition
of substances & the changes
they undergo
 the study of the structure &
properties of matter
 Synthesizing new materials
 Inventing new diagnostic methods
for detection of disease
 Using bacteria to produce
chemicals
An observation is something that is
witnessed and can be recorded.
 A theory is an explanation of behavior.
 A law is a summary of observed behavior.

◦ A law tells what happens; a theory is our
attempt to explain why it happens.
 Every
laboratory investigation involves
gathering and recording data and
observations.

Quantitative: information that involves a
measurement of any kind. Any value recorded
directly from a tool is considered quantitative data.
It should always be recorded immediately, along
with its units of measure.

Qualitative: information that is observed using
your senses, instead of a tool like a measuring stick.
This includes such descriptions as color as well as
observations about texture changes and smell.
 ex. fever: touch/thermometer

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Quantitative
Expressed as a quantity.
Contains a number or
quantity.
Mr. Burton is 4 ft tall.
Ms. Dee is 69 yrs old.
Mr. Franck runs 8.5
miles a day.
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Qualitative
Of, relating to quality.
Does not contain a
number or quantity.
Mr. Burton is short.
Ms. Dee is really old.
Mr. Franck runs a lot.

Scientific laws describe things.
They do not explain them.
◦ Isaac Newton knew what gravity did
(he could describe its behavior),
but he could not explain why
gravity did it.
◦ Newton's Law of Gravity: Each
object in the universe attracts
each other body.

Theories inevitably change as more
information becomes available.
 Ex. The motions of the sun and stars have remained virtually
the same over the thousands of years during which humans
have been observing them, but our explanations - our
theories- have changed greatly since ancient times.

A theory is only an interpretation or a
possible explanation of why nature behaves
in a particular way.
Anything that has mass and takes
up space.
 All matter is made up of tiny
particles called atoms.

 Elements - basic unit of matter
 Compound - made of 2 or more atoms
combined
 These are classified as:
 Substances
 definite composition, pure
 uniform throughout (Homogeneous)
 definite melting/boiling point

Heterogeneous Mixture – contains regions
that have different properties from those of
other regions.
◦ nonuniform

Homogeneous Mixture – all regions of the
mixture have the same properties and same
concentration of salt and water.
◦ uniform; a solution
 These are classified as mixtures because
they have:
 variable composition
 physically separable (distallation)
 no definite melting/boiling point

Farm fresh milk
◦ Heterogeneous

Homogenized milk
◦ Homogeneous

Gasoline
◦ Homogeneous

The ocean
◦ Heterogeneous

Oil and vinegar salad dressing
◦ Heterogeneous

Maple syrup
◦ Homogeneous
 consists of a solute and solvent
 (ex: saltwater, air, glass, alloys)
Solid
 definite shape & volume
 locked into position & close together
 vibrates about a fixed point
Liquid
 definite volume
 assumes shape of container
 vibrates about a moving point
 flows
Gas
 assumes shape & volume of
container
 easily compressed & expands
without limit
 vs. vapor
Plasma
 high energy particles
 found in stars
 produces auroras
Physical
• Are properties of an element or compound that
can be observed without a chemical reaction of
the substance.
• Ex. length, color, temp., density
• extensive -amount of matter
(mass, length,…)
• intensive -nature of material
(density, malleability, ....)
Chemical
•
Are properties of an element or compound in
chemical reactions.
• reaction, burning, ...



Water boils@100°C.
◦ Physical Property
Diamonds cut glass.
◦ Physical Property
Water can be
separated by
electrolysis into H &
O.
◦ Chemical Property



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Sugar is dissolved in
water.
◦ Physical Property
Vinegar reacts with
baking soda.
◦ Chemical Property
Yeast acts on sugar
to form carbon
dioxide and ethanol.
◦ Chemical Property
Aluminum has a low
density.
◦ Physical Property
Physical
 change phase, size, shape
 still has same properties as before
Chemical
 change in substance,
(reaction, burning)
 new substance with
different properties



Dry ice, solid
carbon dioxide, is
sublimed at 25°C
◦ Physical Change
Salt is dissolved in
water.
◦ Physical Change
Iron rusts in a
damp environment.
◦ Chemical Change


Gasoline burns in
oxygen.
◦ Chemical Change
Hydrogen peroxide
decomposes to
water and oxygen.
◦ Chemical Change

Law that states …

ex. Think of cutting a piece of aluminum foil
into smaller and smaller pieces. How far can it
be cut?
◦ smallest particle of an element that
retains its properties
◦ are very tiny particles that form the
building blocks for all matter.
◦ Each element is made up of only one
kind of atom.

Elements - Substances
that contain only one
type of atom.

Graphite and diamond
are both elemental
carbon
◦ For example, pure
aluminum contains only
aluminum atoms

elemental copper
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There are 118 (book: 115) known elements;
93 (book 88) occur naturally on earth. The 25
elements not found on earth are derived
artificially
All artificially derived elements are radioactive
with short half-lives.
Many element names and symbols have Greek
& Latin roots.
Many of the more recently discovered
elements are named after countries or famous
scientists.

Compound - substances made by bonding
atoms together in specific ways. Theses
substances contain two or more different
types of atoms
Plastic = C31H24N4O4
Glucose = C6H12O6



If you enlarge the
proton to the size of a
golf ball the electrons
travel in a cloud that is
2 miles in diameter.
There are 6.5 x 1021
(septillion) atoms in a
drop of water.
That’s
6,500,000,000,000,000
,000,000 atoms in one
drop!
◦ no
 can be divided into: ?
 fundamental building blocks of all
atoms
◦ PROTON:
 Symbol: (p+
 Charge: (+1)
 Location:
nucleus
 atomic mass:
1.00 u
◦ NEUTRON:
 Symbol: (n)
 Charge: (0)
 Location:
nucleus
 atomic mass:
1.00 u
◦ ELECTRON:
 Symbol: (e-)
 Charge: (-1)
 Location:
electron
cloud
 atomic mass:
1/1837 u
An electron is 0.0001 times the mass of a proton.
It is generally considered to have no mass.
◦ Nucleus:
 small dense core, contains nearly all
the mass and has a (+) charge
 contains the protons and the neutrons
◦ Electron Cloud:
 the “empty space” of the atom,
contains the electrons and so has a (-)
charge
◦ Atomic Number (Z)
 equals # of protons in nucleus
(NEVER changes)
 discovered by Moseley
 Z = # of e- in a neutral atom (+ = -)
◦ Mass Number (A)
 measurement in amu
 1 amu = 1/12 mass of a C atom
 Mass Number = number of protons +
number of neutrons
 A=p+n
OR
# of n = A – Z
 ALWAYS a whole number

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
Protons = Atomic Number
Electrons = Atomic Number
for a neutral atom
Neutrons = Mass number Atomic Number
Sample 1
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31 P
15
How many protons are there in the nucleus
of a phosphorus atom?
How many electrons does a neutral atom of
phosphorus have?
How many neutrons are there in the nucleus
of a phosphorus atom?
40 Ca
20
How many protons are there in the nucleus of
a calcium atom?
 How many electrons does a neutral atom of
calcium have?
 How many neutrons are there in the nucleus of
a calcium atom?



Two or more forms of atoms of the same element
with different masses.
Atoms contain the same number of protons but
different numbers of neutrons.
◦ Example:
◦ Boron-10 (10B) has 5 protons and 5 neutrons
◦ Boron-11 (11B) has 5 protons and 6 neutrons
10B
11B

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
All atoms of an element have the same
atomic number and therefore the same
number of protons.
However, for many elements, the number of
neutrons can vary.
Isotopes are atoms of the same element with
different numbers of neutrons.
# Neutrons = Mass Number - # Protons
12
6
C
6 protons
12 - 6 = 6
6 neutrons
13
6
C
6 protons
13 - 6 = 7
7 neutron
14
6
C
6 protons
14 - 6 = 8
8 neutrons


Both isotopes have
only 1 proton.
Tritium has 2
neutrons that are
not present in the
stable form of
hydrogen.

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
The mass of an element depends on
both the mass and the relative
abundance of each element’s isotopes.
The average atomic mass of an element is found by
multiplying the atomic mass of each isotope by its
relative abundance (expressed in decimal form) and
adding the results.
This is why the atomic mass found on the periodic
table is often not a whole number.
Average Atomic Mass = (rel. abund.) x (iso. mass) + (rel.
abund.) x (iso. mass) + (rel. abund.) x (iso. mass) + …..
 average of all isotopes of an element
 Cl-35; actual mass: 34.9689 u @ 75.771%
 Cl-37; actual mass: 36.9659 u @ 24.229%
Calculate:
(34.9689 u) x (75.771%) =
(36.9659 u) x (24.229%) = +
26.496 u
8.9565 u
35.453 u
 What
Mg?
is the average atomic Mass of
◦ Mg-26 11.01%
◦ Mg-25 10.00%
◦ Mg-24 78.99%

Average Atomic Mass =
(0.7899 x 24) + (0.1000 x 25) + (0.1101 x 26)
= 24.32 amu
Names of the following groups:
IA: Alkali Metal
IIA: Alkaline Earth Metal
IIIB-IIB: Transition Metal
VIA: Chalcogen
VIIA: Halogen
VIIIA: Noble Gases
Inner Transition Metal
 conduct electricity/heat, malleable, lustrous,
ductile, tenacious, lose electrons (+ #’s),
high melting point, left of line
 Insulators, nonmalleable, dull, non-ductile,
brittle, low melting point, gain electrons (#’s), right of line
 properties of both
 follows zig-zag line (except Al)
 molecules made of 2 atoms
 ex. H2, O2, N2, F2, I2, Cl2, Br2
Hydrogen gas, oxygen gas, …..
 atom with a charge
 atoms gain or lose electrons to become
stable
 gaining results in a negative (-) charge;
more electrons than protons
 losing results in a positive (+) charge;
more protons than electrons

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

The Lithium Atom (Li) has
3 protons and 3 electrons.
The Lithium Ion (Li+) has
3 protons and only 2
electrons.
The Fluorine atom (F) has
9 protons and 9 electrons.
The Fluorine ion (F-) has 9
protons and 10 electrons.

Magnesium Atom (Mg)
◦ 12 protons
◦ 12 electrons
◦ No Charge

The Magnesium Ion(Mg+2)
◦ 12 protons
◦ 10 electrons
◦ +2 charge
◦ 1st Atomic Theory:
 Democritus
 atomos: indivisible
◦ Dalton’s Atomic Theory
 All matter is composed of atoms
 All atoms of same element are identical and
atoms of different elements are not identical
 Atoms unite in simple ratios to form
compounds
 Reactions occur when atoms are joined,
separated or rearranged, but a reaction can not
change 1 atom into another
 “solid sphere”
◦ J.J. Thomson: used a cathode ray tube to
discover electrons
 cathode ray: collection of very small
negatively charged particles moving at
high speeds
 (ex. TV picture tube)



J.J. Thomson:
used a cathode-ray
tube to discover electrons
Streams of negatively charged particles
were found to emanate from cathode tubes.
ex. TV picture tube
J. J. Thompson is credited with the discovery
of electrons (1897).
◦ Thomson
 “Plum-pudding
model”
◦ E. Rutherford
 discovered the nucleus (positively
charged)
 Demo-chain-linked fence
Ernest Rutherford
shot  particles at
a thin sheet of
gold foil and
observed the
pattern of scatter
of the particles.
Since some
particles were
deflected at large
angles,
Thompson’s model
could not be
correct.


Rutherford postulated a very small, dense
nucleus with the electrons around the
outside of the atom.
Most of the volume of the atom is empty
space.
◦ Rutherford
 “Donut model“
◦ Bohr
 “Planetary Model“
◦ J. Chadwick
 discovered the neutron