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Chapter 3 & 4 – Models of Earth and Chemistry
Lesson 3.1 - Reference Points on Maps -Geographic Pole
The points at which Earth’s axis of rotation intersects Earth’s surface are used as reference points for
defining direction.
These points are the geographic North Pole and South Pole.
Equator
Halfway between the poles, a circle called the equator divides Earth into the North and Southern
Hemispheres.
A reference grid that is made up of additional circles is used to locate places on Earth‘s surface.
Latitude
One set of circles describes positions north and south of the equator.
These circles are known as parallels, and they express latitude.
Parallel any circle that runs east and west around Earth and that is parallel to the equator; a line of latitude.
Latitude the angular distance north or south from the equator; expressed in degrees.
Latitude is measured in degrees, and the equator is 0° latitude. The latitude of both the North Pole and the
South Pole is 90°.
Meridian
East-west locations are established by using meridians.
A meridian is any semicircle that runs north and south around Earth from North to South
It is a line of longitude.
Longitude the angular distance east or west from the prime meridian; expressed in degrees.
The meridian that passes through Greenwich, England is called the prime meridian.
This meridian represents 0° longitude.
Longitude
The meridian opposite the prime meridian, halfway around the world, is labeled 180°, and is called the
International Date Line.
The Global Positioning System
GPS is a satellite navigation system that is based on a global network of 24 satellites that transmit radio
signals to Earth’s surface.
A GPS receiver held by a person on the ground receives signals from three satellites to calculate the
latitude, longitude, and altitude of the receiver on Earth.
Lesson 3.2 - Topographic Maps
One of the most widely used maps is called a topographic map, which shows the surface features of Earth.
Topography the size and shape of the land surface features of a region.
Elevation the height of an object above sea level.
Advantages of Topographic Maps
One of the advantages to using a topographical map is that it shows the three dimensional lay of the land.
It does this by using contour lines.
Contour Lines
On topographic maps, elevation is shown by using contour lines.
Contour line is a line that connects points of equal elevation on a map.
Contour Interval
The difference in elevation between one contour line and the next is called the contour interval.
Every fifth contour line is darker than the four lines one either side of it.
This index contour makes reading elevation easier
Spacing of Contour Lines
The spacing and direction of contour lines indicate the shapes of the landforms represented on a
topographic map.
Closely spaced contour lines indicate that the slope is steep.
Widely spaced contour lines indicate that the land is relatively level.
Valley on Contour Maps
A contour line that bends to form a V shape indicates a valley.
The V always points upstream, (upside down in the picture) or in the direction from which the water might
flow.
Hilltop on Contour Maps
Contour lines that form closed loops indicate a hilltop.
Closed loops that have short straight lines perpendicular to the inside of the loop indicate a depression.
Lesson 4.1 - Chapter 4 - Chemistry of Earth - Distinguishing Properties
Distinguishing Properties
All matter has two types of distinguishing properties—physical properties and chemical properties.
Physical Properties
Physical properties are characteristics that can be observed without changing the composition of the
substance.
Physical properties include density, color, hardness, freezing point, boiling point, and the ability to conduct
an electric current.
Chemical Properties
Chemical properties are characteristics that describe how a substance reacts with other substance to
produce different substances.
Theory of Atoms
By the early 20th century, there was rather compelling evidence that matter could be described by an
atomic theory - atoms.
In 1897, J.J. Thomson showed that electrons have negative electric charge and come from ordinary matter.
Atoms
For matter to be electrically neutral, there must also be positive charges lurking somewhere.
The breakthrough came in 1911 when Ernest Rutherford conducted an experiment intended to determine
the angles through which a beam of alpha particles (helium nuclei) would scatter after passing through a
thin foil of gold.
The majority of alpha particles hardly scattered at all - But there were alpha particles that scattered through
angles greater than 90 degrees.
Model of an Atom
The only model of the atom consistent with this Rutherford experiment is that a small central core (the
nucleus) houses the positive charge and most of the mass of the atom.
While the majority of the atom’s volume contains electrons orbiting the central nucleus.
Atom
The atom is the most basic unit of matter and consists of three types of subatomic particles—protons,
electrons, and neutrons.
Atomic Nucleus
The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons.
Proton
Proton a subatomic particle that has a positive charge and that is located in the nucleus of an atom.
The number of protons determines the identity of the element.
Neutron
A neutron is a subatomic particle that is located in the nucleus of an atom and has no charge.
Neutrons and protons are almost exactly the same size and mass and form the nucleus of an atom.
Electron
An electron is a subatomic particle that has a negative charge and is found outside of the nucleus.
Electrons are much smaller than neutrons and protons -The mass of a proton is 1840 times greater than the
mass of an electron.
A neutral atom has equal numbers of electrons and protons.
The Electron Cloud
The electrons of an atom move in a certain region of space called an electron cloud that surrounds the
nucleus.
The charge of a proton and an electron are equal in magnitude, yet opposite in sign.
They are electrically attracted to each other and this attraction holds electrons in the atom.
Atomic Mass
The atomic mass of an element it determined by the amount of protons and neutrons in its nucleus.
The mass of a subatomic particle is too small to be expressed easily in grams, so a special unit called the
atomic mass unit (amu) is used.
Lesson 4.2 Isotopes
Although all atoms of a given element contain the same number of protons, the number of neutrons may
differ.
Isotopes
Isotope is an atom that has the same number of protons (or the same atomic number) as the other atoms of
the same element do but that has a different number of neutrons (and thus a different atomic mass).
Because of their different number of neutrons and their different masses, different isotopes of the same
element have slightly different properties.
Radioactive Carbon Isotopes
Carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon.
The atomic number of carbon is 6 which means that every carbon atom has 6 protons, so that the neutron
numbers of these isotopes are 6, 7 and 8 respectively.
Radioactive Carbon
Of the three naturally occurring isotopes of carbon on Earth: 99% of the carbon is carbon-12, 1% is carbon13, and carbon-14 occurs in trace amounts.
The half-life of carbon-14 is 5,730±40 years.
The primary natural source of carbon-14 on Earth is found in the atmosphere.
Ultraviolet radiation creates radioactive Carbon-14 (6 protons and 8 neutrons), which then decays back
into nitrogen-14 (7 protons and 7 neutrons) through beta decay.
Radioactive Carbon Dating
Consumed by organic materials, its presence is the basis of the radiocarbon dating method pioneered
by Willard Libby and colleagues (1949), to date archaeological, and geological samples.
Radioactive Uranium Dating
An example of a naturally occurring isotope is uranium-238.
It decays through a series of steps to become a stable form of lead.
Radioactive Carbon Dating
Uranium-lead dating is usually performed on the mineral zircon.
It is used on older matter because it has the longest half-life of 4.5 billion years.
Average Atomic Mass
Because isotopes of an element have different masses, the periodic table uses an average atomic mass of
each element.
Periodic Table
The periodic table is based on the Periodic Law which states that the physical and chemical properties of
the elements recur in a systematic and predictable way when the elements are arranged in order of
increasing atomic number.
Elements in the periodic table are arranged in periods (rows) and groups (columns).
Each of the seven periods is filled sequentially by atomic number.
Groups include elements having the same electron configuration in their outer shell, which results in group
elements sharing similar chemical properties.
Elements
As of November 2011, 118 elements have been identified, the latest being ununseptium in 2010.
Of the 118 known elements, only the first 92 are known to occur naturally on Earth.
Atoms
Hydrogen and helium are by far the most abundant elements in the universe.
However, iron is the most abundant element (by mass) making up the Earth, and oxygen is the most
common element in the Earth's crust.
Valence Electrons
The electrons in the outer shell are termed valence electrons.
Valence electrons determine the properties and chemical reactivity of the element and participate in
chemical bonding.
The Roman numerals found above each group specify the usual number of valence electrons.
Valence Electrons Shell
The elements that form each group commonly have the same number of valence electrons.
An electron shell is an orbit followed by electrons around an atom's nucleus.
The closest shell to the nucleus is called the "1 shell" (also called "K shell"), followed by the "2 shell" (or "L
shell") and so on farther and farther from the nucleus.
Each shell can contain only a fixed number of electrons: The 1st shell can hold up to two electrons, the 2nd
shell can hold up to eight electrons.
Carbon
Carbon (C) has _____ number of shells and ____ number of valence electrons.
Sodium
Sodium (Na) has _____ number of shells and ____ number of valence electrons.
Neon
Neon (Ne) has _____ number of shells and ____ number of valence electrons.
Sulfur
Sulfur (S) has _____ number of shells and ____ number of valence electrons.
Stable Atoms- Gas
When an atom has 8 valence electrons, it is considered stable, or chemically unreactive.
Unreactive atoms do not easily lose or gain electrons and all these elements are gases.
Unstable Atoms- Metals
Elements whose atoms have only one, two, or three valence electrons tend to lose electrons easily.
These elements have metallic properties and are classified as metals.
Unstable Atoms- Non Metals
Elements whose atoms have from four to seven valence electrons are more likely to gain electrons.
These elements are classified as nonmetals.
Molecules
Molecule a group of atoms that are held together by chemical forces.
Most things around us are made of groups of atoms bonded together into packages called molecules.
The atoms in a molecule are held together because they share or exchange electrons.
Molecules are made from atoms of one or more elements.
Some molecules are made of only one type of atom.
For instance, two oxygen atoms bond together to form O2, the part of the air that we need to breath to
survive.
Protein Molecules
Other molecules are very large.
Protein molecules, for example, often contain hundreds of atoms.
Compounds
Elements rarely occur in pure form in Earth’s crust and generally occur in combination with other elements.
Compound a substance made up of atoms of two or more different elements joined by chemical bonds.
Difference Between Compounds and Molecules
The properties of a compound differ from the properties of the elements that make up the compound.
A compound is a molecule that contains at least two different elements.
All compounds are molecules but not all molecules are compounds.