7th Grade Science
Midterm Review
What is science?
• Science is the study of the natural world.
– Science is divided up into three areas:
• Biology/Life science
• Geology/Earth science
• Physics/Physical science
What is empirical evidence?
• The observations, measurements, and other
types of data that people gather and test to
support and evaluate scientific explanations.
What is a theory?
• The explanation for some phenomenon that is
based on observation, experimentation, and
reasoning; that is supported by a large
quantity of evidence; and that does not
conflict with any existing experimental results
or observations.
What is a law?
• A descriptive statement or equation that
reliably predicts events under certain
conditions.
What is the difference between a
theory and a law?
• Theory is an explanation for why something is
the way it is and law describes what is
happening in the natural world.
Where do scientists get their
evidence?
• In the field
• In the laboratory
How do scientific ideas change?
• By new evidence
• By collaboration and debate
What is an experiment?
• An organized procedure to study something
under controlled conditions.
What is an observation?
What is a hypothesis?
What is an independent variable?
What is a dependent variable?
What is data?
What are the steps of the scientific
method? (Please refer to your notes and
foldable)
What is repetition? What is
replication? What is the difference
between them?
What characterizes a good scientific
investigation?
How do you evaluate the quality of
scientific information?
What is a model?
How do scientists organize data?
What are the different types of graphs
and why do we use them?
Unit 2: Study Guide
What is a mineral? How are minerals
formed?
• A mineral is a naturally occurring usually
inorganic solid that has a definite crystalline
structure and chemical composition.
• Minerals are formed:
– As magma and lava cool
– By metamorphism
– From solutions
What is an element?
• Elements are pure substances that cannot be
broken down into simpler substances by
ordinary chemical means
What is a compound?
• A substance made up of atoms or ions of two
or more different elements joined by chemical
bonds.
What is the difference between silicate
and nonsilicate minerals?
• Silicate minerals contain silicon and oxygen,
normally in the form of silicate tetrahedrons.
• Nonsilicate minerals do not.
What are the different properties that can
be used to identify minerals? Define each
property.
• Color- color of the mineral
• Streak- color of the powdered form of the mineral.
(Remember: that if a scientist draws on a white tile with the
mineral, this is how the streak is found.)
• Luster- way a surface reflects light
• Cleavage and Fracture- The way the mineral breaks/splits
• Density- measure of how much matter in a given amount of
space.
• Hardness- mineral’s resistance to being scratched.
• Special Properties- any property specific to the mineral
Know the three different rock types: What are
they? How are they each created?
• Igneous rock forms when magma or lava cools
and hardens
• Sedimentary rock forms from compressed or
cemented layers of sediment.
• Metamorphic rock forms from other rocks as a
result of intense heat, pressure, or chemical
processes.
What is weathering?
• Weathering is the natural process by which
atmospheric and environmental agents, such
as wind, rain, and temperature changes,
disintegrate and decompose rocks.
What is erosion?
• Erosion is the process by which wind, water,
ice, or gravity moves soil and sediment from
one location to another.
What is deposition?
• Deposition is the process in which material is
laid down.
What is the rock cycle?
• The rock cycle is the series of processes in
which rock forms, changes from one type to
another, is destroyed, and forms again by
geologic processes.
• Look in your book on page 78 for a diagram of
the rock cycle.
What is uplift?
• Uplift is the rising of regions of Earth’s crust to
higher elevations.
What is subsidence?
• Subsidence is the sinking of regions of the
Earth’s crust to lower elevations.
What is a rift zone?
• A rift zone is an area of deep cracks that forms
between two tectonic plates that are pulling
away from each other.
What are Earth’s compositional layers?
(Make sure you can label them)
Crust
Mantle
Core
What is convection? Where does convection
take place in Earth and why is it important?
• Convection is the movement of matter due to
differences in density that are caused by
temperature variations; can result in a transfer
of energy as heat.
• Convection takes place in the Earth’s mantle.
• Convection helps rocks move slowing in the
mantle. (Cooler rocks sink and warmer rocks
rise)
What are the Earth’s physical layers?
(Make sure you can label them)
Lithosphere
Asthenosphere
Mesosphere
Outer Core
Inner Core
What is Pangaea? Why is the idea of Pangaea
important in understanding Earth’s history?
• Scientists think that about 245 million years
ago the continents were joined in a single
large landmass that they call Pangaea.
• It’s important to understand that at one time
scientists think that all the continents were
connected and during millions of years the
continents moved into their current locations.
What is sea-floor spreading?
• Sea-floor spreading is the process by which
new oceanic lithosphere sea floor forms when
magma rises to Earth’s surface at mid-ocean
ridges and solidifies, as older existing sea floor
moves away from the ridge.
– Older rock- far from ridge
– Newer rock- formed near ridge
Theory of plate tectonics
• This theory explains how large pieces of the
lithosphere, called plates, move and change
shape.
What is a tectonic plate?
• A tectonic plate is a block of lithosphere that
consists of the crust and the rigid, outermost
part of the mantle.
Different plate boundaries
(Know the arrow diagrams!)
• Convergent- Two plates collide.
• Divergent- Two plates move away from each
other
• Transform- Two plates move past each other
horizontally
What are the three different mechanisms that
cause tectonic plates to move?
• Mantle Convection
• Ridge Push
• Slab Pull
What is an anticline?
(Look on Page 107 for a diagram)
• Anticlines- oldest layers of rock are in the
middle of the fold. The youngest rocks are
towards the outside.
Anticlines are shaped like a:
n
What is a syncline?
(Look on Page 107 for a diagram)
• In syncline folds the youngest rocks are in the
middle and the older rocks are on the outside
edges.
Synclines are shaped like a:
u
Faults
• Strike-Slip Faults
– Formed when rocks are under shear stress and at
transform boundaries
• Normal Faults
– Formed when rocks undergo tension and at
divergent boundaries
• Reverse Faults
– Formed when rocks undergo compression and at
convergent boundaries
Faults
• Be able to label a diagram of each fault, with
where the hanging wall, footwall and fault
plane are! (Look on page 109)
Three types of mountains
• Folded Mountains- Form when rock layers are
squeezed together and pushed upward.
– Usually at convergent boundaries
• Volcanic Mountains- Form when melted rock
erupts onto Earth’s surface
• Fault-Block Mountains- Form when tension
makes the lithosphere break into many normal
faults. Along the faults, pieces of the lithosphere
drop down compared with other pieces. The
pieces left standing form fault-block mountains.
What is an earthquake?
• Earthquakes are ground movements that occur
when blocks of rock in Earth move suddenly and
release energy.
• Label #6 page 116 in your book.
– Know that the Focus is the point underneath the Earth
– The Fault Line is the line between both of the plates
– The Epicenter is on the Earth’s surface.
Label a volcano
• Label #5 on page 126 in your book.
– Know this!
– Know magma is underneath the Earth & lava is
when it has reached the Earth’s surface
Three types of volcanoes
• Shield Volcanoes- Broad base, gently sloping
sides, and form from mild eruptions.
• Cinder Cones- Steep volcano formed from
violent eruptions
• Composite Volcanoes- Alternates between
mild and violent eruptions.
Where do volcanoes occur?
• Divergent boundaries
• Convergent boundaries
• Hot Spots
Unit 3 Review
Please see pages 145-194 in your book for more
information
*This study guide is just to get you started
studying– please look at your notes and book
too.*
What is uniformitarianism?
• A principle that geological processes that
occurred in the past can be explained by
current geologic processes.
What is climate?
• The weather conditions in an area over a long
period of time.
What is a fossil?
• The trace or remains of an organism that lived
long ago, most commonly preserved in
sedimentary rock.
What is a trace fossil?
• A fossilized structure, such as a footprint or
coprolite, that formed in sedimentary rock by
animal activity on or within soft sediment.
What is an ice core?
• A long cylinder of ice obtained from drilling
through ice caps or ice sheets; used to study
past climates.
How do organisms become preserved
as fossils?
•
•
•
•
Fossils can be trapped in amber or asphalt
Buried in rock
Become frozen
Become petrified
What can fossils tell us?
• Fossils tell scientists about changes to the
environment
• Fossils tell scientist how life forms have
changed over time
How does sedimentary rock show
Earth’s history?
• The composition of sedimentary rock show
the source of the sediment that makes up the
rock
• The texture of the sedimentary rock shows the
environment in which the sediment was
carried and deposited
• Features in the rock show what was
happening to the sedimentary rock
What do Earth’s surface features tell
us?
• How continents move
• How landforms change over time
What other materials tell us about
Earth’s climate history?
• Trees
• Sea-Floor sediments
• Ice cores
What is relative dating?
• Any method of determining whether an event
or object is older or younger than other
events or objects.
What is superposition?
• A principle that states that younger rocks lie
above older rocks if the layers have not been
disturbed.
What is unconformity?
• A break in the geologic record created when
rock layers are eroded or when sediment is
not deposited for a long period of time.
What is a geologic column?
• An ordered arrangement of rock layers that is
based on the relative ages of the rocks and in
which the oldest rocks are at the bottom.
How are undisturbed rock layers
dated?
• Older layers are on the bottom
• Younger layers are on the top
How are sedimentary rock layers
disturbed?
•
•
•
•
Tilting
Folding
Faults and Intrusions
Unconformities
How are rock layers ordered?
• Law of crosscutting relationships states that:
“A fault or a body of rock, such as an intrusion,
must be younger than any feature or layer of
rock that the fault or rock body cuts through.”
How are fossils used to determine
relative ages of rocks?
• Fossils can help us determine the relative age
of rocks by giving us a reference point for the
rocks.
• Younger fossils= younger rocks
• Older fossils= older rocks
What is absolute dating?
• Any method of measuring the age of an event
or object in years.
What is radioactive decay?
• The process in which a radioactive isotope
tends to break down into a stable isotope of
the same element or another element.
What is half-life?
• The time required for half of a sample of a
radioactive isotope to break down by
radioactive decay to form a daughter isotope.
• If you have 6 milligrams of the original isotope
in one half-life 3 milligrams of the isotope
would be left and 3 milligrams would be the
daughter isotope
What is radiometric dating?
• A method of determining the absolute age of
an object by comparing the relative
percentages of a radioactive parent isotope
and a stable daughter isotope.
How can the absolute age of rock be
determined?
• Thru absolute dating methods
What is the best rock for radiometric
dating?
• Igneous rock
What are some radiometric dating
methods?
• Radiocarbon dating
• Potassium-Argon dating
• Uranium-Lead dating
How is radiometric dating used to
determine the age of Earth?
• Radiometric dating can be done on meteorites
to determine the age of the Earth.
How are index fossils used?
• Index fossils are markers for the time that
organisms lived on Earth
• Index fossils can date different layers of Earth