7th Grade ScienceMidterm 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 CoreInner 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