Chapter 12 Science

Question 1

What is the difference between minerals and rocks?

Answer 1

Minerals are inorganic solids found in nature made of two or more compounds and have a definite chemical composition. Rocks are solid inorganic material that is made of two or more minerals.

Question 2

Compare and contrast the 2 types of igneous rocks and give an example of each.

Answer 2

Intrusive rocks are molten rock cooling inside the Earth’s surface (ex: granite).
Extrusive rocks are molten rock cooling outside of the Earth’s surface (ex: obsidian)

Question 3

Compare and contrast the 3 types of sedimentary rocks and give an example of each.

Answer 3

Detrital rocks are rocks made from sediments compacted and cemented together (ex: shale, sandstone). Chemical rocks are rocks formed from evaporation or precipitation of minerals from water (ex: rock salt, halite). Organic rocks are rocks made from fossils of plants and animals (ex: limestone, coal).

Question 4

Compare and contrast the 2 types of metamorphic rocks and give an example of each.

Answer 4

Foliated rocks are rocks that have visible layers or elongated grains of minerals in different sizes (ex: slate, gneiss). Non-foliated rocks are rocks that lack distinct layers of bands (ex: marble, quartzite).

Question 5

What is the difference between fine/coarse grained rocks and foliated/non-foliated rocks?

Answer 5

Fine-grained rocks are rocks with small crystals. Coarse-grained rocks are rocks with larger crystals. Foliated metamorphic rocks have visible layers or elongated grains of minerals. Non-foliated metamorphic rocks lack distinct layers or bands and have more
color.

Question 6

What is the rock cycle and how is it used?

Answer 6

The rock cycle is a model used to describe how rocks are related to one another and how they change from one type to another.

Question 7

What is the difference between mechanical and chemical weathering?

Answer 7

Mechanical weathering is the breaking down of rocks due to nature (ice, animals and plants). Chemical weathering is the chemical breakdown of rocks (acid rain, rust).

Question 8

What is the difference between weathering, erosion, and deposition?

Answer 8

Weathering is a mechanical or chemical process that breaks rocks into smaller pieces. Erosion is the wearing away of and removal of rock or sediments. Deposition is when sediments are placed in a new place due to erosion.

Question 9

Explain the 7 properties that identify minerals.

Answer 9

Cleavage is when minerals break into smooth, regular shapes that reflect light.Fracture is when minerals break into jagged and rough, or smooth and curvy edges. Color is an easy observable property determined by its environment. Streak is the color of the powder scarped off a mineral when rubbed against a hard surface. Luster describes how light reflects from a mineral. Hardness is a mineral’s ability to resist being scratched rated from 1-10. Density is the amount of matter in a given space.

Question 10

What is Moh’s Hardness scale and how is it used?

Answer 10

Moh’s Hardness scale is used to determine a mineral’s ability to be scratched. It is on a rating scale of 1-10.

Question 11

What are fossils and who studies them?

Answer 11

Fossils are the remains, imprints, or traces of prehistoric organisms. They are studied by paleontologists

Question 12

Explain the different types of fossil preservations.

Answer 12

Permineralized Remains- occurs when sediments and minerals settle intoopenings of bones and turns them to stone
Imprints- occurs when heat and pressure from surrounding rocks cause liquids and gases to leave a dead organism and a thin film (silhouette) of carbon is left behind
Coal- occurs when large volumes of plant material carbonize and all the structure of the original plant is lost
Mold- occurs when the hard part of a fossil becomes compacted and cemented in rocks where the fossil decays leaving a cavity
Cast- occurs when mineral-rich water or sediments enter and harden in a mold and make a copy of the original fossil
Original Remains- occurs when the soft remains of an organism have been preserved in amber, tar pits or frozen grounds
Trace fossils- reveals the appearance of an animal without showing any part of the animal (tracks, trails, burrows).

Question 13

What are index fossils?

Answer 13

Remains of species that existed on Earth for a relatively short period of time, were abundant and widespread geographically. Used to tell scientists when certain organisms lived during certain time periods.

Question 14

What is the law of superposition and why is it important?

Answer 14

The law of superposition states that in undisturbed rock layers, the oldest rocks are on the bottom and the rocks become progressively younger toward the top. It is important because it tells us the age of rocks and organisms found in those rocks.

Question 15

What are unconformities in rock layers?

Answer 15

Unconformities are gaps in the sedimentary rock layers caused by weathering, erosion, heat or pressure

Question 16

Describe the three types of unconformities.

Answer 16

angular unconformity- when new layers of rock form on the TILTED layers as deposition.
disconformity- when new layers are deposited on top of exposed or eroded rock layers
nonconformity- when layers of sedimentary rock overlie igneous and metamorphic rocks

Question 17

What is the difference between relative and absolute age?

Answer 17

Relative age examines rock sequences to determine the age of something compared to something else. This gives an ESTIMATE of the age. Absolute age examines the materials that make up the object and uses their properties to determine the age, IN YEARS.

Question 18

What is radioactive decay?

Answer 18

Radioactive decay is the breakdown of unstable isotopes into other isotopes and particles where energy can be released.

Question 19

What is half-life?

Answer 19

Half-life is the time it takes for half of the atoms in an isotope to decay.

Question 20

What is the difference between radiometric and radiocarbon dating?

Answer 20

Radiometric dating is the process of calculating the absolute age of a rock using the half-life and the ratio of parent to daughter isotopes to find the absolute age of rocks. Radiocarbon dating is the process of calculating the absolute age of a rock by finding the half-life of Carbon-14 in once living organisms.