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CHEMISTRY, ROCKS, AND MINERALS ATOMS: Are made up of chemical elements. Each element has a nearly identical atoms. Atoms have three different particles: - protons (+) located in center of atom -electrons (-) located around center of atom -neutrons (0) located in center of atom ELEMENT: Elements have the same # of protons and electrons number of protons = number of electrons Isotopes of an element have the same number of protons and electrons, but they have a different number of neutrons. Many isotopes are radioactive and emit energy and ATOMS: Have energy levels, or shells: They surround the nucleus (center of atom) Contain electrons- negatively charged particles WHY ATOMS BOND When an atom’s does not contain a full outer shell, it is likely to form a chemical bond with one or more atoms. A compound: consist of two or more elements that are chemically combined in specific proportions. TYPES OF CHEMICAL BONDS 1. Ionic bonds: form between metal and nonmetal 2. Covalent bonds: form between two non-metals. 3. Metallic bonds: form between two metals. ORGANIC VS. INORGANIC Organic: Made of Carbon and hydrogen Normally living organisms or products of living organisms Inorganic: Made of everything else Normally non-living or man made THE ROCK CYCLE Rocks Rocks are any solid mass of mineral or mineral-like matter occurring naturally as part of our planet. Types of Rocks 1. Igneous rock is formed by the crystallization of molten magma. THE ROCK CYCLE Rocks Types of Rocks 2. Sedimentary rock is formed from the weathered products of preexisting rocks that have been transported, deposited, compacted, and cemented. 3. Metamorphic rock is formed by the alteration of pre-existing rock deep within Earth (but still in the solid state) by heat, pressure. THE ROCK CYCLE The Rock Cycle Shows the relationships among the three rock types (igneous, sedimentary, and metamorphic) Magma is molten material that forms deep beneath the Earth’s surface. Lava is magma that reaches the surface. Weathering is a process in which rocks are broken down by water, air, and living things. Sediment is weathered pieces of Earth elements. THE ROCK CYCLE THE ROCK CYCLE Energy That Drives the Rock Cycle Heat from the Earth’s interior are responsible for forming both igneous rock and metamorphic rock. Weathering and the movement of weathered materials are surface processes powered by energy from the sun. Surface processes produce sedimentary rocks. IGNEOUS ROCKS Formation of Igneous Rocks 1. Intrusive igneous rocks are formed when magma hardens beneath Earth’s surface. 2. Extrusive igneous rocks are formed when lava hardens. IGNEOUS ROCKS Classification of Igneous Rocks Igneous rocks can be classified based on their composition and texture. 1. Texture • Coarse-grained texture is caused by slow cooling resulting in larger crystals. • Fine-grained texture is caused by rapid cooling resulting in smaller mineral grains. COURSE-GRAINED IGNEOUS TEXTURE FINE-GRAINED IGNEOUS TEXTURE IGNEOUS ROCKS Classification of Igneous Rocks 1. Texture (continued) • Glassy texture is caused by very rapid cooling. • Porphyritic texture is caused by different rates of cooling resulting in varied sized minerals. 2. Composition • Granitic composition rocks are made mostly of light-colored quartz and feldspar. OBSIDIAN EXHIBITS A GLASSY TEXTURE. PORPHYRITIC IGNEOUS TEXTURE 3.2 IGNEOUS ROCKS Classification of Igneous Rocks 2. Composition (continued) • Basaltic composition rocks are made mostly of dark-colored silicate minerals and plagioclase feldspar. • Andesitic composition rocks are between granitic light-color minerals and basaltic composition dark-colored minerals. • Ultramafic composition rocks are made mostly from iron and magnesium-rich minerals. BASALT CLASSIFICATION OF IGNEOUS ROCKS SEDIMENTARY ROCKS Formation of Sedimentary Rocks Weathering, Erosion, and Deposition • Erosion involves the weathering and the removal of rock. • Deposition occurs when an agent of erosion—water, wind, ice, or gravity—loses energy and drops sediments SEDIMENTARY ROCKS Formation of Sedimentary Rocks Compaction and Cementation • Compaction is a process that squeezes, or compacts, sediments. • Cementation takes place when dissolved minerals are deposited in the tiny spaces among the sediments. SEDIMENTARY ROCKS Classification of Sedimentary Rocks Two Main Groups 1. Clastic sedimentary rocks are composed of weathered bits of rocks and minerals. • Classified by particle size • Common rocks include - Shale (most abundant) - Sandstone - Conglomerate SHALE WITH PLANT FOSSILS CONGLOMERATE SEDIMENTARY ROCKS Classification of Sedimentary Rocks Two Main Groups 2. Chemical sedimentary rocks form when dissolved substances separate from water. • Common rocks include - limestone—most abundant chemical rock - microcrystalline quartz known as chert, flint, jasper, or agate - evaporites such as rock salt or gypsum - coal FOSSILIFEROUS LIMESTONE CLASSIFICATION OF SEDIMENTARY ROCKS METAMORPHIC ROCKS Formation of Metamorphic Rocks Metamorphism means “to change form.” Form at elevated temperatures and pressures. Found a few kilometers below the Earth’s surface and into the upper mantle. METAMORPHIC ROCKS Formation of Metamorphic Rocks Contact metamorphism occurs when magma moves into rock. • Occurs near a body of magma • Changes are driven by a rise in temperature. 3.4 METAMORPHIC ROCKS Formation of Metamorphic Rocks Regional metamorphism • Directed pressures and high temperatures occur during mountain building. 3.4 METAMORPHIC ROCKS Agents of Metamorphism Heat • Provides the energy needed to drive chemical reactions Pressure • Causes a more compact rock with greater density ORIGIN OF PRESSURE IN METAMORPHISM 3.4 METAMORPHIC ROCKS Classification of Metamorphic Rocks Two main categories 1. Foliated Metamorphic Rock • Has a banded or layered appearance 2. Nonfoliated Metamorphic Rock • Does not have a banded texture CLASSIFICATION OF METAMORPHIC ROCKS GNEISS TYPICALLY DISPLAYS A BANDED APPEARANCE MARBLE — A NONFOLIATED METAMORPHIC ROCK ROCK IMAGES WEBSITE LINK http://geology.com/rocks/ MINERALS Mineral: a naturally occurring, inorganic crystalline material with a unique chemical composition. http://www.feenixx.com/earthscience/Introduction_to_Minerals_Poster.htm MINERALS: Naturally formed- it forms in nature on its own Orderly crystalline structure Solid (cannot be liquid or gas) Has to have a definite chemical composition Has to have a characteristic crystalline structure EXAMPLES OF MINERALS: Glass- can be naturally formed (volcanic glass is called obsidian) Ice- is naturally formed, is a solid, has definite chemical composition Halite (salt)- naturally formed, is solid, has definite crystalline structure. CHARACTERISTICS OF MINERALS Color Streak Luster Crystal form Hardness Cleavage Fracture Density CHARACTERISTIC OF MINERALS- COLOR Color: Small amounts of different elements can give the same mineral different colors. CHARACTERISTIC OF MINERALS- STREAK Streak: is the color of a mineral in its powered form. CHARACTERISTIC OF MINERALS- LUSTER Luster: is used to describe how light is reflected from the surface of a mineral. CHARACTERISTIC OF MINERALS- CRYSTAL FORM Crystal form: is the visible expression of a mineral’s internal arrangement of atoms. CHARACTERISTIC OF MINERALS- HARDNESS Hardness: is a measure of the resistance of a mineral to being scratched. Mohs scale: consists of 10 minerals arranged from 10 (hardest) to 1 (softest) CHARACTERISTIC OF MINERALS- CLEAVAGE Cleavage: is the tendency of a mineral to cleave, or break, along flat, even surfaces. CHARACTERISTIC OF MINERALS- FRACTURE Minerals that do not show cleavage when broken are said to fracture. Fracture: the uneven breakage of a mineral CHARACTERISTIC OF MINERALS- DENSITY Density: is a property of all matter that is the ratio of an object’s mass to its volume.