Matter ch3

Matter

The Blue Planet: Chapter 3

Outline

• Earth Materials

• Organic Matter

• Composition and Internal Structure of the Earth

• Minerals

• Rocks

• Regolith

Earth Materials

• The three common states of matter we are familiar with are solid, liquid and gas

• Materials occurring in the same state can still differ substantially– For example, lava and water are both

liquids; one non-aqueous, one aqueous– Both are very important in a wide variety of

Earth processes

Earth Materials

Earth Materials

Matter can coexist in various states and phases. In (A), matter of uniform composition (H2O) coexists in two different states (liquid and solid) and two different phases (water and ice), separated by physical boundaries. In (B), different phases coexist in the same state (oil and water, both liquids; different types of beans, all solids). In (C), there is only one phase and one state, as is always the case with gases.

Earth Materials

• Chemical elements are the most fundamental substances into which matter can be separated– An atom is the smallest individual particle

that retains the distinctive properties of a given chemical element

• Atoms are built of protons and neutrons in the nucleus and electrons orbiting the nucleus

Earth Materials• The number of protons in the nucleus

of an atom is called the atomic number

• Electrons are considered mass-less• The sum of the neutrons and the

protons in the nucleus is the atomic mass

• Isotopes are atoms with the same atomic number but different mass numbers– Some isotopes are radioactive, and can

be used in radioactive dating

Earth Materials

• An atom is electrically neutral because the positive charge of the protons balances with the negative charge of the electrons

• An atom that has excess positive or negative charge is called an ion– A positive ion is a cation– A negative ion is an anion

Earth Materials• Compounds form when anions and

cations combine to form a bond

• The smallest unit that retains all the properties of a compound is called a molecule

Outline

• Earth Materials

• Organic Matter


• Minerals

• Rocks

• Regolith

Organic Matter

• Possibly the most fundamental compositional distinction is that of organic and inorganic matter– Organic applies specifically to compounds

consisting of carbon atoms bonded together by covalent bonds

– In addition organic implies that the compound is biotic in origin

Organic Matter

• A common characteristic of organic compounds is their tendency to occur in long chain-like structures called polymers

• Important biopolymers in the Earth system– Proteins: chains of bonded amino acids– Nucleic acids: (e.g. DNA) built of nucleotides– Carbohydrates: the basis for most food we

eat, a carbon-hydrogen-oxygen compound

Organic Matter

• Lipids are another important family of organic molecules, which are not polymers and include– Fats and oils– Phospholipids– Waxes– Steroids

Outline

• Earth Materials

• Organic Matter


• Minerals

• Rocks

• Regolith

Composition and Internal Structure of the Earth

• Earth inherited its overall composition from its location in the solar nebula

• Earth has internal layering that originated early in solar system history due to chemical differentiation of the partially molten planet– Layers are distinguished by composition,

rock strength, and state of matter


• There are three major compositional layers in the Earth– Core: metallic iron

solid inner core and liquid outer core

– Mantle: dense rocky matter

– Crust: thin, less dense rocky matter


• The core and mantle have nearly constant thicknesses, but the crust varies in place to place by a factor of 9

• The average oceanic crust is 8 km thick• The average continental crust is 45 km

thick, but ranges from 30-70 km• The two crusts also differ fundamentally

in composition


• Scientific reasoning, indirect sampling, and indirect measurement provide information about the core and mantle that otherwise is inaccessible

• In addition to compositional layering, the Earth contains layers with differences in rock strength


• Mesosphere: “middle sphere” within the mantle

• Asthenosphere: “weak sphere” in the uppermost mantle

• Lithosphere: “rocky sphere” the outermost 100 km


• Of the 92 naturally occurring chemical elements, only 12 occur in Earth’s crust

• The crust is dominated by two elements– Oxygen– Silicon

• With the other ten elements, these are responsible for the composition of all common Earth materials

Outline

• Earth materials

• Organic matter

• Composition and internal structure of the Earth

• Minerals

• Rocks

• Regolith

Minerals

• Minerals are the building blocks of the geosphere, they are or have:– Naturally formed– Inorganic– Solid– Specific chemical composition– Characteristic crystal structure

Minerals

• The two characteristics that best allow the study of minerals are

1. Crystal structure: the way the atoms of the elements are packed together

2. Composition: the major chemical elements that are present and their proportions

Minerals

• Because of their abundance, oxygen and silicon form the basis for the most common rock-forming minerals, and the most common mineral group: silicates

• Other mineral groups include: oxides, sulfides, carbonates, sulfates, and phosphates

Minerals

• Silicates– Built of the silicate

anion (tetrahedron)– The anion joins

together by sharing their oxygen atoms to form chains, sheets and three-dimensional networks

Minerals

Minerals

• Silicates are by far the most abundant minerals in the continental crust, and feldspars are the predominant variety– Feldspars: 60% of minerals in Earth’s crust– Quartz: 15% of minerals in Earth’s crust

– All silicates: 95% of minerals in the crust

• This limits non-silicates to only 5% of the Earth’s crust!

Minerals

• Minerals are identified by their distinct properties that result from their composition and crystal structure– Crystal form and growth habit– Cleavage– Luster– Hardness and specific gravity– Color

Minerals

• Crystal form and growth habit– In 1669, Nicolaus Steno discovered that

the angle between mineral crystal faces is constant and gives each a distinctive crystal form

– He speculated this was due to ordered particles, but proof by use of x-rays would not arrive until 1912

– Crystals only form when a mineral can grow freely in open space

Minerals

Minerals• Cleavage

– A mineral’s tendency to break in preferred directions along weak planar surfaces

• Luster, Color and Streak– The quality and intensity of light reflected from

a mineral surface is luster– Color is often not a reliable means of

identification, as it can be determined by chemical impurities in the composition

– Color in opaque minerals can be a property of grain size, this can be resolved using the mineral’s streak

Minerals

Minerals

• Hardness– This term refers to the relative resistance

of a mineral to being scratched– This is governed by the crystal structure

and the strength of chemical bonds– Hardness is classified using Moh’s relative

hardness scale, which has 10 hardnesses that are not at equal intervals

Minerals

Minerals

• Density and specific gravity– Specific gravity is easier to measure, and

therefore more commonly used– It is the ratio of the weight of the substance

to the weight of an equal volume of pure water

– The densities of some minerals are distinctive; such as gold and galena

Outline

• Earth materials

• Organic matter


• Minerals

• Rocks

• Regolith

Rocks

• A rock is any naturally formed, nonliving, coherent aggregate mass of solid matter that constitutes part of a planet, asteroid, moon, or other planetary object

• Minerals are the most common and abundant building blocks of rocks

Rocks

• There are three families of rocks– Igneous: formed from the cooling and

consolidation of magma or lava– Sedimentary: formed from either chemical

precipitation of material or deposition of particles transported in suspension

– Metamorphic: formed from changing a rock as a result of high temperatures, high pressures, or both

Rocks

• Earth’s crust is mainly igneous and metamorphic rock, however, most of the rock we see at surface is sedimentary

Rocks

• The two main features that best classify rocks are– Texture: the overall appearance of a rock,

resulting from the size, shape, and arrangement of its mineral grains

– Mineral assemblage: the kinds and relative amounts of minerals present

Outline

• Earth materials

• Organic matter


• Minerals

• Rocks

• Regolith

Regolith

• Rock exposed at Earth’s surface is susceptible to alteration by the action of water, wind, and other agents that physically and chemically break it apart and alter it

• This broken-up, disintegrated rock matter is called the regolith

Regolith

• Literally “blanket rock,” the regolith forms a layer draped over most of Earth’s surface

• Three categories describe most of the various materials of the regolith– Saprolite: rock that is weathered in situ– Sediment: loose rock and mineral particles

• Clastic sediment (broken particles)• Chemical sediment (dissolved material)

– Soil: contains organic matter mixed with minerals, can support rooted plants

Regolith

Matter ch3

Environment

Transcript of Matter ch3