Composition of Earth Chapter Matter and Change BIG Idea The variety of substances on Earth results from the way that atoms are arranged and combined Chapter Minerals BIG Idea Minerals are an integral part of daily life Chapter Igneous Rocks BIG Idea Igneous rocks were the first rocks to form as Earth cooled from a molten mass to the crystalline rocks of the early crust Chapter Sedimentary and Metamorphic Rocks BIG Idea Most rocks are formed from preexisting rocks through external and internal geologic processes 56 CAREERS IN EARTH SCIENCE Geologist: This geologist is exploring the internal structures of this giant cave Geologists like this one might collect samples of the rocks and minerals to help describe the origins of the geologic features within the cave Earth Science Visit glencoe.com to learn more about geologists Then write a short magazine article about how a geologist is studying a newly discovered cave To learn more about geologists, visit glencoe.com Unit • Composition of Earth 57 David Boyer/National Geographic Image Collection Matter and Change BIG Idea The variety of substances on Earth results from the way that atoms are arranged and combined New mailbox 3.1 Matter MAIN Idea Atoms are the basic building blocks of all matter 3.2 Combining Matter MAIN Idea Atoms combine through electric forces, forming molecules and compounds 3.3 States of Matter MAIN Idea All matter on Earth and in the universe occurs in the form of a solid, a liquid, a gas, or plasma Mailbox exposed to ice and snow GeoFacts • Only atmospheres that contain oxygen and water cause iron-bearing objects to rust Therefore, the equipment that has been left on the Moon will never rust • Ocher, a red pigment used as a coloring agent, is made from the iron-bearing mineral hematite Rusty mailbox • Mars is red because of abundant iron oxide, also known as rust, in the soil 58 (tl)Royalty-Free/CORBIS, (cr)Doug Wilson/CORBIS, (br)Royalty-Free/CORBIS, (bkgd)Momatiuk - Eastcott/CORBIS Doug Martin Start-Up Activities States of Matter Make the following Foldable to organize information about the four states of matter on Earth LAUNCH Lab What fortified cereals contain? Everything is made up of matter; different types of matter have different properties Some metals, such as iron, cobalt, and nickel, are attracted to magnets STEP Fold a sheet of paper in half lengthwise, and then fold it in half twice more STEP Unfold and cut along the folds of the top flap to make four tabs STEP Label the tabs as follows: Solids, Liquids, Gases, and Plasma Procedure Read and complete the lab safety form Tape a small, strong magnet to the eraser end of a pencil Pour 250 g of dry, fortified cereal into a small, plastic bag Smooth the bag as you close it to release excess air Using a rolling pin, thoroughly crush the cereal in the plastic bag Pour the crushed cereal into a 250-mL glass beaker Add 150 mL of tap water to the beaker Using the pencil-magnet as a stirrer, stir the cereal/water mixture for 10 min, stirring slowly for the last minute Remove the stirrer from the mixture and examine the magnet end of the stirrer with a magnifying lens Analysis Describe what you see on the magnet Determine Study the cereal box to determine what the substance on the magnet might be Solids Liquids Gases Plasma FOLDABLES Use this Foldable with Section 3.3 As you read this section, summarize what you learn about the states of matter Visit glencoe.com to study entire chapters online; explore • Interactive Time Lines • Interactive Figures • Interactive Tables animations: access Web Links for more information, projects, and activities; review content with the Interactive Tutor and take Self-Check Quizzes Section Chapter • XXXXXXXXXXXXXXXXXX • Matter and Change 59 Section Objectives ◗ Describe an atom and its components ◗ Relate energy levels of atoms to the chemical properties of elements ◗ Define the concept of isotopes Review Vocabulary atom: the smallest particle of an element that retains all the properties of that element New Vocabulary matter element nucleus proton neutron electron atomic number mass number isotope ion Matter MAIN Idea Atoms are the basic building blocks of all matter Real-World Reading Link Gold, which is often used in jewelry, is so soft that it can be molded, hammered, sculpted, or drawn into wire Whatever its size or shape, the gold is still gold Gold is a type of matter Atoms Matter is anything that has volume and mass Everything in the physical world that surrounds you is composed of matter On Earth, matter usually occurs as a solid, a liquid, or a gas All matter is made of substances called elements An element is a substance that cannot be broken down into simpler substances by physical or chemical means For example, gold is still gold whether it is a gold brick, coins, or a statue Each element has distinct characteristics You have learned some of the characteristics of the element gold Although aluminum has different characteristics than gold, both aluminum and gold are elements that are made up of atoms All atoms consist of even smaller particles—protons, neutrons, and electrons Figure 3.1 shows one method of representing an atom The center of an atom is called the nucleus (NEW klee us) (plural, nuclei) The nucleus of an atom is made up of protons and neutrons A proton is a tiny particle that has mass and a positive electric charge A neutron is a particle with approximately the same mass as a proton, but it is electrically neutral; that is, it has no electric charge All atomic nuclei have a positive charge because they are composed of protons with positive electric charges and neutrons with no electric charges Figure 3.1 In this representation of an atom, the fuzzy area surrounding the nucleus is referred to as an electron cloud ■ Electron cloud Nucleus Interactive Figure To see an animation of the electron cloud, visit glencoe.com Atom 60 Chapter • Matter and Change PERIODIC TABLE OF THE ELEMENTS Metal 1 Atomic number Symbol H H 18 Metalloid Liquid State of matter Nonmetal Solid Helium Recently observed Synthetic 1.008 Atomic mass 1.008 Hydrogen Element Hydrogen Gas 13 14 15 16 17 He 4.003 Lithium Beryllium Boron Carbon Li Be B C N O F Ne 6.941 9.012 10.811 12.011 14.007 15.999 18.998 20.180 Sodium 11 Magnesium 12 Aluminum 13 Silicon 14 Phosphorus 15 Sulfur 16 Chlorine 17 Argon 18 11 10 Oxygen Fluorine Neon 10 Al Si P S Cl Ar 26.982 28.086 30.974 32.066 35.453 39.948 Gallium 31 Germanium Arsenic Selenium Bromine 30 32 33 34 35 Krypton 36 Zn Ga Ge As Se Br Kr 65.39 69.723 72.61 74.922 78.96 79.904 83.80 Silver 47 Cadmium 48 Indium 49 Tin 50 Antimony 51 Tellurium 52 Iodine 53 Xenon 54 Ag Cd In Sn Sb Te I Xe 106.42 107.868 112.411 114.82 118.710 121.757 127.60 126.904 131.290 Platinum Gold Polonium Astatine Radon Na Mg 22.990 24.305 Potassium 19 Calcium 20 Scandium 21 Titanium 22 Vanadium 23 Chromium 24 Manganese 25 Iron 26 Cobalt 27 Nickel 28 Copper 29 K Ca Sc Ti V Cr Mn Fe Co Ni Cu 39.098 40.078 44.956 47.867 50.942 51.996 54.938 55.847 58.933 58.693 63.546 Rubidium 37 Strontium 38 Yttrium 39 Zirconium 40 Niobium 41 Ruthenium 44 Rhodium 45 Palladium 46 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd 85.468 87.62 88.906 91.224 92.906 95.94 (98) 101.07 102.906 Cesium Barium Lanthanum Hafnium Tantalum Tungsten Rhenium Molybdenum Technetium 43 42 12 Nitrogen Zinc Osmium Iridium Mercury Thallium Lead Bismuth 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 132.905 137.327 138.905 178.49 180.948 183.84 186.207 190.23 192.217 195.08 196.967 200.59 204.383 207.2 208.980 208.982 209.987 222.018 Francium 87 Radium 88 Actinium 89 Rutherfordium 104 Dubnium 105 Seaborgium 106 Bohrium 107 Hassium 108 Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg (223) (226) (227) (261) (262) (266) (264) (277) (268) (281) (272) Meitnerium Darmstadtium Roentgenium 111 110 109 Actinide series * Uut * Uuq * Uup * Uuh (284) (289) (288) (291) Ununoctium 118 * Uuo (294) Samarium 62 Europium 61 63 Gadolinium 64 Terbium 65 Dysprosium 66 Holmium 67 Erbium 68 Thulium 69 Ytterbium 70 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 140.115 140.908 144.242 (145) 150.36 151.965 157.25 158.925 162.50 164.930 167.259 168.934 173.04 174.967 Thorium 90 Protactinium 91 Uranium 92 Neptunium 93 Plutonium 94 Americium 95 Curium 96 Berkelium 97 Californium 98 Einsteinium 99 Fermium 100 Mendelevium 101 Nobelium 102 Lawrencium 103 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 232.038 231.036 238.029 (237) (244) (243) (247) (247) (251) (252) (257) (258) (259) (262) Cerium 58 Praseodymium Neodymium 59 60 (285) Ununtrium Ununquadium Ununpentium Ununhexium 116 113 114 115 names and symbols for elements 112, 113, 114, 115, 116, and 118 are temporary Final names will be *The selected when the elements’ discoveries are verified The number in parentheses is the mass number of the longest lived isotope for that element Lanthanide series Ununbium 112 * Uub Promethium 86 Surrounding the nucleus of an atom are smaller particles called electrons An electron (e‒) has little mass, but it has a negative electric charge that is exactly the same magnitude as the positive charge of a proton An atom has an equal number of protons and electrons; thus, the electric charge of an electron cancels the positive charge of a proton to produce an atom that has no overall charge Notice that the electrons in Figure 3.1 are shown as a cloudlike region surrounding the nucleus This is because electrons are in constant motion around an atom’s nucleus, and their exact positions at any given moment cannot be determined Lutetium 71 ■ Figure 3.2 The periodic table of the elements is arranged so that a great deal of information about all of the known elements is provided in a small space Interactive Figure To see an animation of the periodic table of elements, visit glencoe.com Symbols for elements There are 92 elements that occur naturally on Earth and in the stars Other elements have been produced in laboratory experiments Generally, each element is identified by a one-, two-, or three-letter abbreviation known as a chemical symbol For example, the symbol H represents the element hydrogen, C represents carbon, and O represents oxygen Elements identified in ancient times, such as gold and mercury, have symbols of Latin origin For example, gold is identified by the symbol Au for its Latin name, aurum All elements are classified and arranged according to their chemical properties in the periodic table of the elements, shown in Figure 3.2 Section • Matter 61 ■ Figure 3.3 The element chlorine is atomic number 17 Infer In what state is chlorine at room temperature? Element Atomic number Symbol Atomic mass Chlorine 17 Cl 35.453 State of matter Mass number The number of protons and neutrons in atoms of different elements varies widely The lightest of all atoms is hydrogen, which has only one proton in its nucleus The heaviest naturally occurring atom is uranium Uranium-238 has 92 protons and 146 neutrons in its nucleus The number of protons in an atom’s nucleus is its atomic number The sum of the protons and neutrons is its mass number Because electrons have little mass, they are not included in determining mass number For example, the atomic number of uranium is 92, and its mass number is 238 (92 protons + 146 neutrons) Figure 3.3 explains how atomic numbers and mass numbers are listed in the periodic table of the elements Isotopes Recall that all atoms of an element have the same number of protons However, the number of neutrons of an element’s atoms can vary For example, all chlorine atoms have 17 protons in their nuclei, but they can have either 18 or 20 neutrons This means that there are chlorine atoms with mass numbers of 35 (17 protons + 18 neutrons) and 37 (17 protons + 20 neutrons) Atoms of the same element that have different mass numbers are called isotopes The element chlorine has two isotopes: Cl-35 and Cl-37 Because the number of electrons in an atom equals the number of protons, isotopes of an element have the same chemical properties Look again at the periodic table in Figure 3.2 Scientists have measured the mass of atoms of elements The atomic mass of an element is the average of the mass numbers of the isotopes of an element Most elements are mixtures of isotopes For example, notice in Figure 3.2 that the atomic mass of chlorine is 35.453 This number is the average of the mass numbers of the naturally occurring isotopes of chlorine-35 and chlorine-37 Identify Elements What elements are in your classroom? Most substances on Earth occur in the form of chemical compounds Around your classroom, there are numerous objects or substances that consist mostly of a single element Procedure Read and complete the lab safety form Create a data table with the following column headings: Article, Element, Atomic Number, Properties Name three objects in your classroom and the three different elements of which they are made List the atomic numbers of these elements and describe some of their properties Analysis Categorize List two examples of a solid, a liquid, and a gaseous object or substance Compare and contrast liquids, solids, and gases 62 Chapter • Matter and Change Radioactive isotopes The nuclei of some isotopes are unstable and tend to break down When this happens, the isotope also emits energy in the form of radiation Radioactive decay is the spontaneous process through which unstable nuclei emit radiation In the process of radioactive decay, a nucleus can lose protons and neutrons, change a proton to a neutron, or change a neutron to a proton Because the number of protons in a nucleus identifies an element, decay changes the identity of an element For example, the isotope polonium-218 decays at a steady rate over time into bismuth-214 The polonium originally present in a rock is gradually replaced by bismuth You will learn about the use of radioactive decay to calculate the ages of rocks in Chapter 21 Electrons in Energy Levels Although the exact position of an electron cannot be determined, scientists have discovered that electrons occupy areas called energy levels Look again at Figure 3.1 The volume of an atom is mostly empty space However, the size of an atom depends on the number and arrangement of its electrons Filling energy levels Figure 3.4 presents a model to help you visualize the position of atomic particles Note that electrons are distributed over one or more energy levels in a predictable pattern Keep in mind that the electrons are not sitting still in one place Each energy level can hold only a limited number of electrons For example, the smallest, innermost energy level can hold only two electrons, as illustrated by the oxygen atom in Figure 3.4 The second energy level is larger, and it can hold up to eight electrons The third energy level can hold up to 18 electrons and the fourth energy level can hold up to 32 electrons Depending on the element, an atom might have electrons in as many as seven energy levels surrounding its nucleus Figure 3.4 Electrons occupy one energy level in hydrogen, two energy levels in oxygen, and three energy levels in aluminum ■ Nucleus protons (p) neutrons (n) e– e– e– e– e– e– e– e– e– e– e– e– e– e– Hydrogen atom Oxygen atom e– e– e– e– e– e– e– e– Aluminum atom Section • Matter 63 ■ Figure 3.5 The inert nature of argon makes it an ideal gas to use inside an incandescent light bulb because it does not react with the extremely hot filament e– e– e– e– e– e– e– e– e– e– e– e– e– e– e– e– e– e– Valence electrons The electrons in the outermost energy level determine the chemical behavior of the different elements These outermost electrons are called valence electrons Elements with the same number of valence electrons have similar chemical properties For example, both a sodium atom, with the atomic number 11, and a potassium atom, with the atomic number 19, have one valence electron Thus both sodium and potassium exhibit similar chemical behavior These elements are highly reactive metals, which means that they combine easily with many other elements Elements such as helium and argon have full outermost energy levels For example, an argon atom, shown in Figure 3.5, has 18 electrons, with two electrons in the first energy level and eight electrons in the second and outermost energy levels Elements that have full outermost energy levels are highly unreactive The gases helium, neon, argon, krypton, xenon, and radon have full outer energy levels Argon atom Ions Sometimes atoms gain or lose electrons from their outermost energy levels Recall that atoms are electrically neutral because the number of electrons, which have negative charges, balances the number of protons, which have positive charges An atom that gains or loses an electron has a net electric charge and is called an ion In general, an atom in which the outermost energy level is less than half-full—that is, it has fewer than four valence electrons—tends to lose its valence electrons When an atom loses valence electrons, it becomes positively charged In chemistry, a positive ion is indicated by a superscript plus sign For example, a sodium ion is represented by Na+ If more than one electron is lost, that number is placed before the plus sign For example, a magnesium ion, which forms when a magnesium atom has lost two electrons, is represented by Mg2+ Reading Check Explain what makes an ion positive VOCABULARY ACADEMIC VOCABULARY Region a continuous part of an area or body, with or without definite boundaries or with certain characteristics The region surrounding the flood was labeled as a disaster area 64 Chapter • Matter and Change An atom in which the outermost energy level is more than half-full — that is, it has more than four valence electrons — tends to fill its outermost energy level Such an atom forms a negatively charged ion Negative ions are indicated by a superscript minus sign For example, a nitrogen atom that has gained three electrons is represented by N3‒ Some substances contain ions that are made up of groups of atoms—for example, silicate ions These complex ions are important constituents of most rocks and minerals Abundance of Elements In the Universe In Earth‘s Crust Hydrogen 93.5% Helium 6.3% Oxygen 46.6% Iron 5.0% Oxygen 0.065% Carbon 0.039% Neon 0.009% Nitrogen 0.008% Magnesium 0.004% Silicon 0.004% Iron 0.003% Sulfur 0.002% Calcium 3.6% Sodium 2.8% Silicon 27.7% Potassium 2.6% Magnesium 2.1% All others 1.5% What elements are most abundant? Astronomers have identified the two most abundant elements in the universe as hydrogen and helium All other elements account for less than percent of all atoms in the universe, as shown in Figure 3.6 Analyses of the composition of rocks and minerals on Earth indicate that the percentages of elements in Earth’s crust differ from the percentages in the universe As shown in Figure 3.6, 98.5 percent of Earth’s crust is made up of only eight elements Two of these elements, oxygen and silicon, account for almost 75 percent of the crust’s composition This means that most of the rocks and minerals on Earth’s crust contain oxygen and silicon You will learn more about these elements and the minerals they form in Chapter Section Aluminum 8.1% Figure 3.6 The most abundant elements in the universe are greatly different from the most abundant elements on Earth Hypothesize Where might most of the hydrogen and helium in the universe be found? ■ Assessment Section Summary Understand Main Ideas ◗ Atoms consist of protons, neutrons, and electrons ◗ An element consists of atoms that have a specific number of protons in their nuclei Explain why the elements magnesium and calcium have similar properties ◗ Isotopes of an element differ by the number of neutrons in their nuclei ◗ Elements with full outermost energy levels are highly unreactive ◗ Ions are electrically charged atoms or groups of atoms MAIN Idea Differentiate among the three parts of an atom in terms of their location, charge, and mass Illustrate how a neutral atom becomes an ion Compare and contrast these isotopes: uranium-239, uranium-238, and uranium-235 Think Critically Design an illustration using the concepts of valence electrons and energy levels to explain why oxygen might combine with magnesium Interpret the representation of magnesium in the periodic table Explain why the atomic mass of magnesium is not a whole number MATH in Earth Science As the radioactive isotope radium-226 decays, it emits two protons and two neutrons How many protons and neutrons are now left in the nucleus? What is the atom’s new atomic number? What is the name of this element? Self-Check Quiz glencoe.com Section • Matter 65 Visualizing Bonds Figure 3.12 Atoms gain stability by sharing, gaining, or losing electrons to form ions and molecules The properties of metals can be explained by metallic bonds C S e– Covalent bond Shared electrons fill outermost energy levels and make stable molecular compounds e– e– e– – e– e e– e– e– e– e– e– e– e– + e– e– e– – e– e e– e– e– e– – e e– – e e– e– – – e e– e – e – e– e – e– e e– e– e– – e e– e– – e– e – e– e – e– – e e e– e– e– e– e– e– e– e– – e– e– – e – e e– – e e– e – e e– e– – e– e e– – e– e– e– e – e– e– e – – e e CS2 Ionic bond Once valence electrons are gained or lost to fill outermost energy levels and form stable ions, the oppositely charged ions are attracted to each other Metallic bond Within metals, valence electrons move freely around positively charged protons + + + Mg+2 e– e– e– + + + + + + e– e– e– e– e– e– + e– e– e– e– e– e– e– + + + e– e– e– e– + e– e– e– e– + e– e– + + e– + O–2 e– e– e– e– e– e– e– e– e– e– e– e– e– MgO To explore more about chemical bonding, visit glencoe.com Section • Combining Matter 69 You have learned that atoms gain, lose, or share electrons to become more stable and that these atoms form compounds Sometimes, compounds break down into simpler substances The change of one or more substances into other substances, such as those in Figure 3.13, is called a chemical reaction Chemical reactions are described by chemical equations For example, water (H2O) is formed by the chemical reaction between hydrogen gas (H2) and oxygen gas (O2) The formation of water can be described by the following chemical equation 2H2 + O2 ➞ 2H2O ■ Figure 3.13 When a copper wire is placed in the solution of silver nitrate in the beaker, a chemical reaction occurs in which silver replaces copper in the wire and an aqua-colored copper nitrate solution forms You can read this chemical equation as “two molecules of hydrogen and one molecule of oxygen react to yield two molecules of water.” In this reaction, hydrogen and oxygen are the reactants and water is the product When you write a chemical equation, you must balance the equation by showing an equal number of atoms for each element on each side of the equation Therefore, the same amount of matter is present both before and after the reaction Note that there are four hydrogen atoms on each side of the above equation (2 × = 4) There are also two oxygen atoms on each side of the equation Another example of a chemical reaction, one that takes place between iron (Fe) and oxygen (O), is represented by the following chemical equation 4Fe + 3O2 ➞ 2Fe2O3 You will examine how compounds form in the Problem-Solving Lab on this page PROBLEM-SOLVING Lab Interpret Scientific Illustrations How compounds form? Many atoms gain or lose electrons in order to have eight electrons in the outermost energy level In the diagram, energy levels are indicated by the circles around the nucleus of each element The colored spheres in the energy levels represent electrons, and the spheres in the nucleus represent protons and neutrons Element A 70 Element B Chapter • Matter and Change Analysis How many electrons are present in atoms of Element A? Element B? How many protons are present in the nuclei of these atoms? Use the periodic table on page 61 to determine the name and symbol of Element A and Element B Think Critically Decide if these elements can form ions If so, what would be the electric charges (magnitude and sign) and chemical symbols of these ions? Formulate a compound from these two elements What is the chemical formula of the compound? Tim Courlas Chemical Reactions Mixtures and Solutions Unlike a compound, in which the atoms combine and lose their identities, a mixture is a combination of two or more components that retain their identities When a mixture’s components are easily recognizable, it is called a heterogeneous mixture For example, beach sand, shown in Figure 3.14, is a heterogeneous mixture because its components are still recognizable—shells, small pieces of broken shells, grains of minerals, and so on In a homogeneous mixture, which is also called a solution, the component particles cannot be distinguished, even though they still retain their original properties A solution can be liquid, gaseous, or solid Seawater is a solution consisting of water molecules and ions of many elements that exist on Earth Molten rock is also a liquid solution; it is composed of ions representing all atoms that were present in the crystals of the rock before it melted Air is a solution of gases, mostly nitrogen and oxygen molecules together with other atoms and molecules Metal alloys, such as bronze and brass, are also solutions Bronze is a homogeneous mixture of copper and tin atoms; brass is a similar mixture of copper and zinc atoms Such solid homogeneous mixtures are called solid solutions You will learn more about solid solutions in Chapters and ■ Figure 3.14 Not all mixtures of beach sand and shells are alike Mixtures from the Atlantic Ocean will contain components that are different from mixtures that form in the Pacific Ocean Reading Check Describe three examples of solutions Acids Many chemical reactions that occur on Earth involve solutions called acids and bases An acid is a solution containing a substance that produces hydrogen ions (H+) in water Recall that a hydrogen atom consists of one proton and one electron When a hydrogen atom loses its electron, it becomes a hydrogen ion (H+) The pH scale, shown in Figure 3.15, is based on the amount of hydrogen ions in a solution This amount is referred to as the concentration A value of is considered neutral A solution with a pH reading below is considered to be acidic The lower the number, the more acidic the solution Interactive Figure To see an animation of the pH scale, visit glencoe.com ■ Figure 3.15 The pH scale is not only reserved for science class All substances have a pH value, as you can see by the common household substances shown here Tomato pH Distilled water pH Lemon pH Household ammonia pH 11 Milk pH More acidic Antacid pH 10 Neutral Drain cleaner pH 13 10 11 12 13 14 More basic Section • Combining Matter 71 (tr)Gregor Schuster/zefa/CORBIS, (l to r)Studiohio, (2)Mark Burnett, (3)Studiohio, (4)Matt Meadows, (5)Amanita Pictures, (6)Studiohio, (7)Aaron Haupt Careers In Earth Science Geochemistry Some geochemists study the interaction of rocks, minerals and the environment They can help mining companies reduce the amount of contamination from waste piles by understanding how the rocks and minerals break down and how toxic the byproducts might be For more information on Earth science careers, visit glencoe.com The most common acid in Earth’s environment is carbonic acid (H2CO3), which is produced when carbon dioxide (CO2) is dissolved in water (H2O) by the following reaction H2O + CO2 ➞ H2CO3 Some of the carbonic acid (H2CO3) in the water ionizes, or breaks apart, into hydrogen ions (H+) and bicarbonate ions (HCO3), as represented by the following equation H2CO3 ➞ H+ + HCO3‒ These two equations play a major role in the dissolution and precipitation of limestone and the formation of caves, discussed in Chapter 10 Many of the reaction rates involved in geological processes are very slow For example, it might take thousands of years for enough carbonic acid in limestone to dissolve in groundwater and produce a cave Bases When a solution contains hydroxide ions (OH‒), the solution is called a base A base can neutralize an acid because hydrogen ions (H+) from the acid react with the hydroxide ions (OH‒) from the base to form water through the following reaction H+ + OH‒ ➞ H2O Refer again to Figure 3.15 A solution with a reading above is considered to be basic The higher the number, the more basic the solution Distilled water usually has a pH of 7, but rainwater is slightly acidic, with a pH of 5.0 to 5.6 The pH values of some common substances are shown in Figure 3.15 Section Assessment Section Summary Understand Main Ideas ◗ Atoms of different elements combine to form compounds ◗ Covalent bonds form from shared electrons between atoms Calculate the number of atoms needed to balance the following equation: CaCO + HCl ➞ CO2 + H2O + CaCl ◗ Ionic compounds form from the attraction of positive and negative ions ◗ There are two types of mixtures— heterogeneous and homogeneous ◗ Acids are solutions containing hydrogen ions Bases are solutions containing hydroxide ions MAIN Idea Explain why molecules not have electric charges Differentiate between molecules and compounds Diagram how an acid can be neutralized Compare and contrast mixtures and solutions by using specific examples of each Think Critically Design a procedure to demonstrate whether whole milk, which consists of microscopic fat globules suspended in a solution of nutrients, is a homogeneous or heterogeneous mixture Predict what kind of chemical bond forms between nitrogen and hydrogen atoms in ammonia (NH3) Sketch this molecule Earth Science Antacids are used to relieve indigestion and upset stomachs Write an advertisement for a new antacid product Explain how the product works in terms that people who are not taking a science class will understand 72 Chapter • Matter and Change Self-Check Quiz glencoe.com (tl)Biophoto Associates/Photo Researchers, (tr)Charles D Winters/Photo Researchers, (br)Mark A Schneider/Photo Researchers, (bkgd)Doug Martin/Photo Researchers Section 3.3 Objectives ◗ Describe the states of matter on Earth ◗ Explain the reasons that matter exists in these states ◗ Relate the role of thermal energy to changes in state of matter Review Vocabulary chemical reaction: the change of one or more substances into another substance New Vocabulary crystalline structure glass evaporation plasma condensation sublimation ■ Figure 3.16 This granite is composed of mineral crystals that fit together like interlocking puzzle pieces The minerals that make up the rock are composed of individual atoms and molecules that are aligned in a crystalline structure States of Matter MAIN Idea All matter on Earth and in the universe occurs in the form of a solid, a liquid, a gas, or plasma Real-World Reading Link When your skin is wet, even on a hot day, it usu- ally feels cool — especially if it is windy How can warm air feel cold? When the water evaporates, it absorbs heat from your skin The harder the wind blows, the more water evaporates and the colder your skin becomes Solids Solids are substances with densely packed particles, which can be ions, atoms, or molecules Most solids are crystalline structures because the particles of a solid are arranged in regular geometric patterns Examples of crystals are shown in Figure 3.16 Because of their crystalline structures, solids have both a definite shape and volume Perfectly formed crystals are rare When many crystals form in the same space at the same time, crowding prevents the formation of perfect crystals with smooth boundaries The result is a mass of intergrown crystals called a polycrystalline solid Most solid substances on Earth, including rocks, are polycrystalline solids Figure 3.16 shows the polycrystalline nature of the rock granite Some solid materials have no regular internal patterns Glass is a solid that consists of densely packed atoms arranged randomly Glasses form when molten material is chilled so rapidly that atoms not have enough time to arrange themselves in a regular pattern These solids not form crystals, or their crystals are so small that they cannot be seen Window glass consists mostly of disordered silicon and oxygen (SiO2) Biotite mica Quartz Pink feldspar Section • States of Matter 73 Liquids ■ Figure 3.17 Each of these containers has the same volume of liquid in it Explain why the liquids are not all at the same level in the containers At any temperature above absolute zero (−273°C), the atoms in a solid vibrate Because these vibrations increase with increasing temperature, they are called thermal vibrations At the melting point of the material, these vibrations become vigorous enough to break the forces holding the solid together The particles can then slide past each other, and the substance becomes liquid Liquids take the shape of the container they are placed in, as you can see in Figure 3.17 However, liquids have definite volume Reading Check Explain the effect that increasing temperature has on the atoms in solids Gases FOLDABLES Incorporate information from this section into your Foldable The particles in liquids vibrate vigorously As a result, some particles can gain sufficient energy to escape the liquid This process of change from a liquid to a gas at temperatures below the boiling point is called evaporation When any liquid reaches its boiling point, it vaporizes quickly as a gas In gases, the particles are separated by relatively large distances and they travel at high speeds in one direction until they bump into another gas particle or the walls of a container Gases, like liquids, have no definite shape Gases also have no definite volume unless they are restrained by a container or a force such as gravity For example, Earth’s gravity keeps gases in the atmosphere from escaping into space Plasma When matter is heated to a temperature greater than 5000°C, the collisions between particles are so violent that electrons are knocked away from atoms Such extremely high temperatures exist in stars and, as a result, the gases of stars consist entirely of positive ions and free electrons These hot, highly ionized, electrically conducting gases are called plasmas Figure 3.18 shows the plasma that forms the Sun’s corona You have seen matter in the plasma state if you have ever seen lightning or a neon sign Both lightning and the matter inside a neon tube are in the plasma state ■ Figure 3.18 The Sun’s temperature is often expressed in kelvins; –273 K is equal to 0°C The Sun’s corona, which is a plasma, has a temperature of about 15,000,000 K Compare the temperature of the corona to lightning, which is 30,000 K 74 Chapter • Matter and Change (t)John Evans, (b)SOHO/NASA PhotoAlto/SuperStock Changes of State Solids melt when they absorb enough thermal energy to cause their orderly internal crystalline arrangement to break down This happens at the melting point When liquids are cooled, they solidify at that same temperature and release thermal energy The temperature at which liquids solidify is called the freezing point When a liquid is heated to the boiling point and absorbs enough thermal energy, vaporization occurs and it becomes a gas When a gas is cooled to the boiling point it becomes a liquid in a process called condensation, shown in Figure 3.19 Energy that was absorbed during vaporization is released upon condensation Evaporation can occur below the boiling point when thermal vibrations enable individual atoms or molecules to escape from a solid You might have noticed that even on winter days with temperatures below freezing, snow gradually disappears This slow change of state from a solid (ice crystals) to a gas (water vapor) without an intermediate liquid state is called sublimation Conservation of Energy The identity of matter can be changed through chemical reactions and nuclear processes, and its state can be changed under different thermal conditions You have learned that a chemical equation must be balanced because matter cannot be created or destroyed This fundamental fact is called the law of conservation of matter Like matter, energy cannot be created or destroyed, but it can be changed from one form to another For example, electric energy might be converted into light energy This law, called the conservation of energy, is also known as the first law of thermodynamics Section 3.3 Figure 3.19 As the hot, moist air from the shower encounters the cool glass of the mirror, the water vapor in the air condenses on the glass Predict What would happen if the glass were the same temperature as the air? ■ Assessment Section Summary Understand Main Ideas ◗ Changes of state involve thermal energy ◗ The law of conservation of matter states that matter cannot be created or destroyed Apply what you know about thermal energy to compare evaporation and condensation ◗ The law of conservation of energy states that energy is neither created nor destroyed Infer how the boiling point of water (100°C) would change if water molecules were not polar molecules MAIN Idea Explain how thermal energy is involved in changes of state Evaluate the nature of the thermal vibrations in each of the four states of matter Think Critically Consider glass and diamond—two clear, colorless solids Why does glass shatter more easily than diamond? MATH in Earth Science Refer to Figure 3.18 Calculate the corona’s temperature in degrees Remember that 273 K is equal to 0ºC Self-Check Quiz glencoe.com Section • States of Matter 75 Digital watch displays are made possible through LCD technology The inset photograph shows a polarized light micrograph of a LCD What is a liquid crystal? You know that liquids and crystals are two states of matter; but how is it possible to be both a liquid and a crystal? Recall that particles in a liquid can slide past each other in a container, while particles in a solid are packed together and cannot move separately Liquid crystals are long molecules that keep their orientation — if they were oriented side-to-side in a thin layer on a glass plate, they would keep that side-to-side orientation Because of their liquid property, the crystals can move around almost like a school of fish Therefore, they share characteristics with both solids and liquids This unique property makes them useful for a variety of electronic applications How LCDs work? Consider a digital watch, for example If you look closely at it, you can see the numbers, even when they are not darkened These are the tracks that are engraved in the middle layer of a display “sandwich.” Two plates of glass make up the outer portion of this sandwich The inner portion of the sandwich, the tracks, contains liquid crystals that are in their natural, “relaxed” state In the relaxed state, light passes through the plates of glass, and is reflected out 76 Chapter • Matter and Change If an electric current is applied across a track of liquid crystals, the crystals lose their original orientation As long as a small current passes through them, light entering the plates of glass will not be reflected In other words, that track will appear black Seems simple enough, right? That is why LCD displays are becoming more and more popular They can be all black or color There are, however, some flaws with LCD technology that need to be corrected For example, it has a narrow viewing angle; if you tilt your watch slightly you can no longer see the numbers as clearly, if at all With further research, however, LCD might just become the vision of the future Earth Science Diagram Visit glencoe.com to research the different layers of an LCD Create a drawing showing all the different layers and how they fit together (l)Hugh Threlfall/Alamy Images, (r)Michael W Davidson/Photo Researchers You wake up in the morning, glance at your alarm clock, and get ready for school You microwave your breakfast, grab your music player and dash out the door, checking your wristwatch as you go Once at school, you pull out your calculator and get ready for the big math exam Did you know you have used liquid crystal display (LCD) technology five times already? LCD is common display technology, used often because it is thin, lightweight, and energy efficient PRECIPITATE SALTS Background: Many rocks on Earth form from salts precipitated from seawater Salts precipitate when a salt solution becomes saturated Solubility is the ability of a substance to dissolve in a solution When a solution is saturated, no more of that substance can be dissolved Question: Under what conditions salt solutions become saturated, and under what conditions does salt precipitate out of solution? Suggested materials Place the beaker on the hot plate, and turn on the hot plate Stir the solution until the last few grains of sodium chloride dissolve The salt solution will then be saturated Pour 50 mL of the warm, saturated solution into the second 250-mL glass beaker, and cover it with plastic wrap so that it forms a seal Put this beaker in the refrigerator Pour 50 mL of the saturated solution into the glass baking dish Place the dish on the hot plate and heat the salt solution until all the liquid evaporates WARNING: The baking dish will be hot Handle with care Place the original beaker with 50 mL of the remaining solution on a shelf or windowsill Do not cover the beaker Observe both beakers one day later If crystals have not formed, wait another day Once crystals have formed in all three containers, observe the size and shape of the crystals Write your observations in your data table Analyze and Conclude Materials halite (sodium chloride) 250-mL glass beakers (2) distilled water plastic wrap laboratory scale hot plate shallow glass baking dish refrigerator glass stirring rod Safety Precautions Procedure Read and complete the lab safety form Make a data table to record your observations Pour 150 mL of distilled water into a 250-mL glass beaker Add 54 g of sodium chloride and stir until only a few grains remain on the bottom of the beaker Describe the shape of the precipitated crystals in the three containers Does the shape of the crystals alone identify them as sodium chloride? Infer how heating the salt solution affected the solubility of the sodium chloride Interpret what effect cooling has on the solubility of salt What effect does evaporation have on the solubility of salt? Evaluate the relationship between rate of cooling and crystal size INQUIRY EXTENSION Use Other Substances Design an experiment to investigate other soluble substances Test to see how much of the substance can be dissolved in a given amount of water, how long it takes for the solution to evaporate, and what crystal shapes form Prepare a short report to share with your class GeoLab 77 Matt Meadows Download quizzes, key terms, and flash cards from glencoe.com BIG Idea The variety of substances on Earth results from the way that atoms are arranged and combined Vocabulary Key Concepts Section 3.1 Matter • atomic number (p 62) • electron (p 61) • element (p 60) • ion (p 64) • isotope (p 62) • mass number (p 62) • matter (p 60) • neutron (p 60) • nucleus (p 60) • proton (p 60) MAIN Idea Atoms are the basic building blocks of all matter • Atoms consist of protons, neutrons, and electrons • An element consists of atoms that have a specific number of protons in their nuclei • Isotopes of an element differ by the number of neutrons in their nuclei • Elements with full outermost energy levels are highly unreactive • Ions are electrically charged atoms or groups of atoms Section 3.2 Combining Matter • acid (p 71) • base (p 72) • chemical bond (p 67) • chemical reaction (p 70) • compound (p 66) • covalent bond (p 67) • ionic bond (p 68) • metallic bond (p 68) • molecule (p 67) • solution (p 71) Atoms combine through electric forces, forming molecules and compounds Atoms of different elements combine to form compounds Covalent bonds form from shared electrons between atoms Ionic compounds form from the attraction of positive and negative ions There are two types of mixtures—heterogeneous and homogeneous Acids are solutions containing hydrogen ions Bases are solutions containing hydroxide ions MAIN Idea • • • • • Section 3.3 State of Matter • condensation (p 75) • crystalline structure (p 73) • evaporation (p 74) • glass (p 73) • plasma (p 74) • sublimation (p 75) 78 Chapter X • Study Guide All matter on Earth and in the universe occurs in the form of a solid, a liquid, a gas, or plasma • Changes of state involve thermal energy • The law of conservation of matter states that matter cannot be created or destroyed • The law of conservation of energy states that energy is neither created nor destroyed MAIN Idea Vocabulary PuzzleMaker glencoe.com Vocabulary PuzzleMaker biologygmh.com Vocabulary Review Fill in the blank with the correct vocabulary term from the Study Guide The electrically neutral particles in the nucleus of an atom are called The of an element is equal to the number of in the nucleus of its atoms Atoms of an element that differ by their mass numbers are called 13 Which element does this atom represent? (Refer to the periodic table of the elements in Figure 3.2.) A helium B beryllium C lithium D nitrogen 14 What ionic compound is formed by the ions Al3+ and O2‒? C Al2O3 A Al3O2 B Al2O D AlO Use the figure below to answer Question 15 Explain how both terms in each set below are related ionic, covalent homogeneous mixture, solution acid, base Arrange each set of vocabulary terms into a meaningful and true sentence solid, glass molecules, ions, plasma, gas evaporation, condensation 10 electrons, metallic bond Understand Key Concepts Use the figure below to answer Questions 11 to 13 e– e– e– 11 What is the atomic number of this atom? A C B D 12 How many valence electrons does this atom have? A C B D Chapter Test glencoe.com 15 The figure shows the arrangement of atoms in a substance What is this substance? A gas B glass C liquid D solid 16 Which is an example of a heterogeneous mixture? A coffee B soil C gelatin D air 17 During the process of sublimation, into what is ice converted? A hydrogen ions and hydroxide ions B hydrogen C water D water vapor 18 Many musical instruments are made of brass, which is a mixture of copper and zinc atoms What is brass an example of? A solid solution B ionic compound C chemical reaction D base Chapter • Assessment 79 19 What happens to the thermal energy of a gas when it condenses and forms a liquid? A It is released B It is absorbed C It increases in temperature D It decreases in temperature Use the figure below to answer Questions 28 and 29 e– p p e– 20 What kind of ion characterizes an acid? A oxygen ion B negative ion C hydroxide ion D hydrogen ion e– p p e– Constructed Response 21 Explain why table salt does not conduct electricity 22 Explain why gases such as neon and argon not react with other elements 23 Illustrate a model atom of potassium (K), indicating the positive charge of the nucleus and the idealized positions of the electrons in the various energy levels Is potassium a metal or nonmetal? Refer to the periodic table of the elements in Figure 3.2 Use the figure below to answer Questions 24 and 25 28 Identify the type of bond shown in the figure Explain your reasoning 29 Compare this bond to a metallic bond Use an illustration to clarify your answer 30 Deduce what the difference would be between water molecules containing deuterium and those containing ordinary hydrogen atoms (Hint: Deuterium is an isotope of hydrogen with mass number two It forms the same chemical compounds as other hydrogen atoms, including water.) 31 Evaluate the statement: Plasma is usually hotter than gas Think Critically Hydrogen Lithium Sodium 11 Potassium 19 H Li Na K 1.008 6.941 22.990 39.098 24 Detect What these elements have in common? 25 Explain why the atomic masses of these elements are not whole numbers 26 Distinguish which kind of chemical bond produces a solid that readily conducts heat and electricity 27 Compare and contrast the physical properties of the elements helium and neon 80 Chapter • Assessment Use the figure below to answer Question 32 e– e– e– e– e– e– 32 Deduce The figure shows an atom of carbon-14 This radioactive isotope decays by converting one of its neutrons to a proton What element and isotope is produced by the radioactive decay of carbon-14? Chapter Test glencoe.com 33 Illustrate Use an illustration to show why water is effective in dissolving ionic solids such as table salt 34 Group and list some of the properties that all metals have in common 35 Assess the correctness of the following statement: Snow that covers the ground can disappear on cold days even when the temperature remains below 0°C 36 Arrange When hydrochloric acid (HCl) is added to the sedimentary rock limestone (CaCO3), carbon dioxide (CO2), calcium chloride (CaCl2) and water (H2O) are given off Arrange the chemical compounds listed above into a balanced equation that shows this chemical reaction 37 Hypothesize Earth’s upper atmosphere—the ionosphere — conducts electricity Hypothesize about the state of matter in the ionosphere 38 Careers in Earth Science Assess the importance of understanding chemical reactions in order to interpret the conditions of rocks and minerals that are present on other planets 39 Estimate Air at sea level has a density of 0.13 g/L Estimate how much air, in kilograms, fills your classroom (Hint: to start, multiply the length, width, and height of your classroom to calculate the room’s volume.) Concept Mapping 40 Create a concept map using the following terms or phrases: ionic bond, covalent bond, metallic bond, shared electrons, gain or lose electrons, a sea of electrons, molecule, and compound Challenge Question 41 An atom is mostly empty space A typical atom has a diameter of 10‒10 m with a nucleus of diameter 10‒14 m To visualize this, enlarge this atom by a factor of 108 (100 million) so that its nucleus has the size of a marble (1 cm) What would be the diameter of this enlarged atom? Would this atom fit into a football field? Chapter Test glencoe.com Additional Assessment 42 Earth Science Prepare a news release reporting on the discovery of a new chemical element The element has 121 protons in its nucleus Be sure to include the characteristics of this element and its location in the periodic table Document–Based Questions Data obtained from: Mineral resource of the month: magnesium Geotimes: 50, no 11 (November 2005): 57 Magnesium is lightweight and has a high strengthto-weight ratio It constitutes about percent of the crust and its concentration in seawater is 0.13 percent Magnesium is present in more than 60 minerals and is produced from magnesium-bearing ores, seawater, and brines Magnesium is made into an alloy with aluminum to increase strength and corrosion resistance, especially in beverage cans Its light weight makes it useful in aircrafts, cars, chain saws, lawn mowers, and other machine parts Annual world magnesium production is 584,000 metric tons China produces the most at 426,000 metric tons Yearly production in the United States, is 43,000 metric tons and U.S consumption is 140,000 metric tons per year Canada, China, Israel, and Russia supply 92 percent of U.S magnesium imports Recycling covers about 15 percent of U.S magnesium consumption 43 Determine the amount of magnesium in m3 of seawater Express your answer in kilograms 44 Analyze and explain the role of magnesium in the manufacture of cars and beverage cans 45 Compare and contrast the production of magnesium in the United States and other countries How does U.S dependence on imports affect these other countries? Cumulative Review 46 Why is the concept of time and scale in the study of Earth science difficult to understand? (Chapter 1) 47 In the collection of data, measurements must follow what general guidelines? (Chapter 1) Chapter • Assessment 81 Standardized Test Practice Multiple Choice Use the table below to answer Questions 1–3 Atomic Structure Element Atomic Number Atomic Mass Beryllium 9.01 Calcium 20 40.08 Silicon 14 28.09 Scandium 21 44.96 Titanium 22 47.88 Zirconium 40 91.22 If titanium has 22 protons in its nucleus, how many neutrons are present in the nucleus of its most common isotope? A 26 B 28 C 48 D 60 If the most common isotope of scandium has 24 neutrons in its nucleus, how many protons does scandium have? A 13 B 21 C 45 D 66 If calcium’s most common isotope has 20 neutrons in its nucleus, how many neutrons can be found in another naturally occurring isotope of calcium? A 21 B 30 C 41 D 60 Determine the number of valence electrons that oxygen has A B C D 82 Chapter • Assessment How should a city that is located between two time zones establish a time? A Have two different times within the same city B Allow the people to choose what time zone they want to go by C Move the time zone split outside of the city D Divide the time in half to split the difference of the two times Use the illustration below to answer Questions 6–8 0°C 120°C In a cup, an ice cube melts in liquid water Which is true at the moment the ice melts? A The water has less thermal energy than the ice B The water has more thermal energy than the ice C The water is at a higher temperature than the ice D The water is at the same temperature as the ice According to the illustration, what happens to water molecules when water is heated? A Their energy levels decrease B They move farther apart C They move more slowly D They stop moving In order for a liquid to change to a gaseous state, what must it reach? A its freezing point B its condensation point C its melting point D its boiling point Which is the most acidic? A banana (pH 4.7) B celery (pH 5.9) C grape (pH 3.0) D lettuce (pH 6.9) Standardized Test Practice glencoe.com Reading for Comprehension Short Answer Use the graph below to answer Questions 10–12 Anthocyanin Pigments Temperature (°C) Heating Curve Evaporation/ condensation 100°C Red cabbage contains a pigment molecule called flavin (an anthocyanin) This water-soluble pigment is also found in apple skin, plums, poppies, cornflowers, and grapes Acidic solutions will turn anthocyanin a red color Neutral solutions result in a purplish color Basic solutions appear in greenishyellow Therefore, it is possible to determine the pH of a solution based on the color it turns the anthocyanin pigments in red cabbage juice Gas Liquid Melting 0°C Solid Thermal energy How to make red cabbage pH indicator About: Chemistry (Online resource accessed February 12, 2007.) 10 The diagram represents a sample of water What does it demonstrate? 17 How does red cabbage act as an acid/base indicator? A Its pigment changes color based on the acid or base with which it comes in contact B Its pigment will not change when it comes into contact with a neutral solution C It always stays red D Its pigment releases water when it comes in contact with an acid or base 11 At which point does the water have the least amount of thermal energy? 12 What the level lines in the diagram represent? 15 Does silicon have any isotopes? Explain your answer 18 What can be inferred from this passage? A Red cabbage is the only food that can act as an indicator of acids and bases B Anthocyanin pigments in red cabbage juice change color when exposed to acids or bases C It is safe to eat the cabbage after using it for an acid/base experiment D The change in color does not indicate an acid or base 16 Ethical scientific researchers accurately report the data on which they base their conclusions Why is this important? 19 What color does the cabbage become when exposed to a base? A purplish color C blue color B red color D greenish-yellow color 13 Differentiate between a theory and a hypothesis 14 Why would a geologic map be important to a scientist studying earthquakes? NEED EXTRA HELP? If You Missed Question Review Section 10 11 12 13 14 15 16 3.1 3.1 3.1 3.1 2.1 3.3 3.3 3.3 3.2 3.3 3.3 3.3 1.3 2.2 3.1 1.3 Standardized Test Practice glencoe.com Chapter • Assessment 83 ... the universe, as shown in Figure 3.6 Analyses of the composition of rocks and minerals on Earth indicate that the percentages of elements in Earth s crust differ from the percentages in the universe. .. temperature, they are called thermal vibrations At the melting point of the material, these vibrations become vigorous enough to break the forces holding the solid together The particles can then slide... Hypothesize Earth s upper atmosphere the ionosphere — conducts electricity Hypothesize about the state of matter in the ionosphere 38 Careers in Earth Science Assess the importance of understanding