Focus on California 8th Grade Physical Science Textbook Chapter 2 The Nature of Matter

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Chapter The Nature of Matter ( Standards Preview ) Elm at the more than too menu of matter has and I distinct structure . All forms of matter are ! one 01 more ! the . As I lasts for this Students know that compounds are at mo ! more and that ( pounds have that ave from thew elements are in which atoms are rearranged into of A I basis lot Students know the idea of atoms the ol mat ter In chemical the num bu at atoms stays who run malt haw they ( slay know ( heat at heat . muons is made by asking questions and a basis lav this mutant and addressing the mutant the other three minds , develop their own and . Students wil a Plan and conduct A to test a thus Junk at an made ! metal tan .

Introduction to Matter ( the BIG Idea What is chemistry ?

Check What You Know Suppose you have a whole cookie . You break the cookie into tiny pieces and crumbs . Then , you weigh all the pieces and crumbs . How do you think the weight of the whole cookie compares to the total weight of all the cookie crumbs ?

Gupta ! 53 EM The Images shown here represent some of the key In this chapter Vou can use this vocabulary skill to help you understand the meaning of some key terms in this chapter . Prefixes A is a word part that is added at the beginning of a root word to ( hange its meaning . For example , the prefix means with , or together . In the word combine , the is added to the root word bind to form , meaning to bind together tie bind or tie together The following prefixes will help you learn new words in this chapter . Prefix Meaning Example Word i i Apply It ! The Greek root therm means Use the table to learn the meaning of the prefix . Then predict the meaning of the adjective . Read Section to see if your predicted definition is accurate or needs to be changed . endothermic change )

Chapter Vocabulary Section was matter chemical property element atom ( bond compound ( formula heterogeneous mixture homogeneous mixture Section an . change law 01 ( of mallet Section energy temperature thermal energy endothermic change ( energy energy energy 701 Build Vocabulary ( Web ( ode ( Owner ! 55

' Reading skin Identify the Main Idea The mam idea as the most bI ( In passage of text Sometimes the mam Idea stated At other you must the mam yourself Here are some tips . Look at the or . the Important a few about the ( State the mam idea of the passage . Read the paragraph on page 58 Identify the main idea and supporting You can keep track of information by using a organizer the one below . Main Idea Matter anything that has mass and takes up space The around you is matter . Apply It ! In your notebook , copy and complete the . As you read the chapter , look for the main ideas and supporting details in paragraphs .

Classify Changes in Matter Look . All sorts changes are taking plate . You might observe a fence rusting or puddle ol water evaporating . As you will learn in this , changes in matter ( an be physical or . In this investigation , you will keep a log of the changes that occur around you . Your Goal To identify and observe physical and chemical changes in your daily life and to record evidence lor those ( To the investigation , you must determine what indicates that a change has taken place ( observations of the different you notice your life during one week classify the ( you observe as physical or chemical follow the safety guidelines in Appendix A Plan It ! the chapter to learn what physical and chemical are . with a group , discuss some changes you observe regularly Try to ( if eath change ' is a physical or change .

can Focus Students know that pounds are ( armed by combining two or more diflerent elements and that compounds have ties that are from their constituent elements . What kinds of properties are used to describe matter ?

What are elements , and how do they relate to compounds ?

What are the properties at a mixture ?

Key Terms matter I substance physical property I properly clement atom chemical bond molecule compound I chemical mixture I heterogeneous mixture homogeneous mixture I solution Describing Matter What Is a Mixture ?

row teacher WI give you a handful of objects , such as checkers , marbles , and paper clips of different sizes and colors . Examine the objects , Then sort them into at least three groups , Each item should be grouped with similar items . Describe the differences between the unsorted handful and the sorted groups of . Then make a list of the characteristics of each sorted group . Think it Over Forming Operational Definitions The unsorted handful of objects represents a mixture . Vour sorted groups represent substances . Using your observations . infer what the terms mixture and substance mean . You ' aIl ) the word . Think about how you the oi . or i Icy , the ' In science . this word has meaning . Matter is anything that has mass and lakes up space . All the ' you is . and you arc . Aii . glam , paper . and oi these are . Paper . ceramic , wood , metal . and foam are all forms of matter .

Properties of Matter Even though air and plastic are both matter . no one has to tell you they are materials . Matter can have many ent properties . or characteristics . Materials can be hard or soft , rough or smooth . hot or cold . liquid . solid . or gas , Some rials catch easily . but others do not burn . Chemistry is the study of the properties and how matter changes . The properties and changes of any type of matter depend on its makeup . Some types of matter are substances and some are not . chemistry , a is a single kind of matter that is pure . meaning it always has it a set of properties . For example , table salt has the same composition and properties no matter where it comes or a salt mine . On the other hand . think about the batter for blueberry . contains , butter , sugar , salt , blueberries . and other ingredients shown in Figure . While some of the ingredients . such as sugar and salt . are pure substances . the batter is not . It consists of eral ingredients that can vary with the recipe . Every form of matter has two kinds of properties and chemical properties . A physical property of oxygen is that it is a gas all room temperature . chemical property of oxygen is that it reacts with iron to form read more about physical and chemical in the next two pages . Pun substances Table salt , table sugar , and baking soda are put substances . Haunt Substances or Not ?

Making muffin batter involves mixing together different kinds of matter . The batter itself is not a pure substance . Classifying Why are salt . sugar . and baking soda pure substances ?

Not substances Flour , baking powder , milk , eggs , and are not pure substances .

Flaunt Physical Properties The physical properties of matter help you identify and classify matter in its different forms . Applying Concepts Why is melting point a physical property ?

Interpreting Data Melting point is the ture at which a solid becomes a liquid . Boiling point isthe temperature at which a liquid becomes a gas . look at the data listed below . Identify each substance physical state at room temperature ( approximately 200 . Is it a gas . a liquid , or a solid Explain your conclusions . Melting Bolling ( Water 100 Ethanol 79 Propane Table salt 301 600 A Density and Melting Point . The density 01 ice at is grin . Above , ice will liquid water . Texture and Color Bumpy texture and bright colors are physical properties of this hungry chameleon . A Metal becomes a shiny , flexible toy when shaped into a flat wire and coiled . Physical Properties of Matter A physical property is a characteristic of a pure substance that can be observed without it intu substance . For , a property of water is that it freezes at a temperature of ' hi liquid water . it to ice . but it is still water . texture . and color are some other physical properties of matter . you describe a substance as a solid . at liquid . or a gas , you are stating another physical property . Whether or not a substance dissolves in water is at physical property . too . Sugar will dissolve in water . but iron will not . Stainless steel is mostly iron . so you can stir into tea with a stainless steel spoon . Physical properties can be used to classify matter . For . two properties of metals are luster and the ability to conduct heat and electricity . Some metals . such as iron . can be ' by a magnet . are also . which they can be bent into shapes . They can also be pressed into sheets and pulled into long , thin wire . materials such as glass . brick . and will break into small pieces ifyou try to bend them or press them .

Flaunt Chemical Properties The chemical oi different forms of matter can not be observed without changing a substance into a new substance . Flammability Wood fire , producing heal . gases , and ash . Ability to Run iron can form turning a once shiny car into a crumbling relic . Chemical Properties of Matter physical ties of matter . some properties ca be observed just by ing at or touching a substance . A property is a characteristic of a pure substance that describes its ability to change into substances . To the properties of a substance , you must try to change it to another substance . Like physical properties . chemical properties are used to classify substances . For , a chemical property ( natural gas ) is that it can catch tire and burn in air , When it burns . it with in the air and forms new substances . water and carbon . Burning , or . is a chemical property methane as well as the substances in wood or gasoline . One chemical property is that it will combine slowly with oxygen in air to turm a . rust . Silver will react with in the air to form tarnish . in contrast . a ical property gold is that it does mat react easily with oxygen 01 ' Bakers make use of a chemical properly the stances in bread dough . With the help of ) added to the dough , some of these substances can produce a gas . which muses the bread to rise . What is property ?

New Substances . New Properties Gases produced during baking create spaces In freshly made bread , Gupta ! Examples of Elements Some elements have familiar uses . Many elements are at room temperature , but some are gases or liquids . bat Tungsten wire I Elements What is matter ?

Why is one kind of matter from another kind of matter ?

Educated people in ancient Greece debated these questions . Around 450 ( a Greek named Empedocles proposed that all matter was made of four elements , earth . lire . and water . lle thought that all other matter was a combination of two or more ofthese four elements . The idea of four elements was so convincing that people believed it for more than ! years . What Is an Element ?

In the late . experiments by Lhe earliest chemists began to show that matter was made up of many more than four elements . Now , scientists know that all matter in the universe is made more than ferent substances , still called elements . An element is a pure substance that can not be broken down into any other stances by chemical or physical means . Elements are the simplest substances . Each element can be by its physical and chemical properties . You are already familiar with some elements . Aluminum . which is used to make foil and outdoor furniture . an ment . Pennies are made from zinc . another element . Then the ! pennies are given it coating of copper , also an element . With each breath . you inhale the elements oxygen and nitrogen . which make up 99 percent of atmosphere . Elements are For Links on matter often represented by or symbols . such as for carbon . for oxygen , for hydrogen . and for zinc .

Particles of What is the smallest piece of an element ?

Suppose you could keep tearing a I piece of aluminum foil in half over and over again . Would you ' led made . graphite . a form of carbon . reach a point where you have the smallest possible piece of , aluminum ?

The answer is yes . Since the early , scientists in this book are shown have known that all matter is made of atoms . An atom is the ' basic particle from which all elements are made . Different have properties their atoms are . Experiments in the early showed that an atom is made of even smaller parts . at the diagram ofa carbon atom in Figure . The atom has a positively charged center . or nucleus . that contains smaller particles . It is surrounded by a cloud of negative charge . You will learn more about the structure of atoms in Chapter . Spherical model of a carbon atom when Atoms Combine Atoms of most elements have the ability to combine with other atoms . When atoms combine . they form a chemical bond . which is a force of attraction Nucleus between two atoms . many cases . atoms combine to form larger particles molecules ( uh ) of two or more atoms held together by chemical bonds . A of water . for example . consists of an oxygen atom cally bonded to two hydrogen atoms . Two atoms of the same ment can also combine to form a molecule . Oxygen molecules Electron cloud consist of two atoms . Figure shows models of three mod of molecules . You will see similar models throughout this book . atom electron cloud and the particles in the nucleus . What is molecule ?

Hours Modeling Molecules Models of molecules often consist of colored spheres that stand for different kinds of atoms . How many atom are In a molecule of carbon dioxide ?

molecule oxygen molecule Carbon one carbon atom Two hydrogen One oxygen atom Two oxygen atoms Two oxygen atoms Gunner ! no Ratios A ratio compares two numbers . it tells you how much you have of one item compared to how much you have of another . For example , a cookie recipe calls for cups of every cup of sugar . You can write the ratio of flour to sugar as to , or I . The chemical formula for rust , a compound made from the elements iron ( Fe ) and oxygen ( Oi . may be written as , In this compound , the ratio of iron atoms to oxygen atoms is . This compound is from . a compound in which the ratio of iron atoms to oxygen atoms is I . Practice Problem What is the ratio of nitrogen atom ( to oxygen atoms ( in a compound with the formula ?

Is it the same as the compound , Explain . how Compounds From Elements This shell is made mostly of calcium a compound made from calcium . carbon . and oxygen . 640 Compounds matter is made of elements . but most elements in are found combined with other . A compound is a pure substance made of two or more elements chemically in a set ratio . A compound may be represented by zi , which shows the in the pound and the ratio . For example , part of the gas you exhale is carbon dioxide . its chemical is ( 203 . The number below the symbol for oxygen tells you that the ratio of carbon to oxygen is I to . If there is no number after the symbol , the number I is understood ) If a different ratio of carbon atoms and oxygen atoms are seen in , you have a different compound . For example . carbon gas produced in car the formula ( Here . the ratio atoms to oxygen atoms is to When elements chemically combined , they form compounds having properties that are different from those of the uncombined elements . For example , the element sulfur is El yellow solid , and the clement silver is at shiny metal . But when silver and sulfur ) form it compound called silver , You would call this black compound . sugar ( is a compound made of the elements carbon . hydrogen , and oxygen . sugar crystals do not . the gases oxygen and hydrogen or the black bon you see in charcoal . what does a formula tell you , compound ?

Calcium carbonate ( oxygen ( 02 ) Mixtures ' and compounds are pun ) but most of the you see every day are not . Instead . they are mixtures . A mixture is made of two or more . compounds . or are together in the some place hut are not combined . Mixtures from in two ) Each substance in a mixture keeps its properties . Also . the parts of a mixture are not in at set ratio . Think ofa handful of moist mil as that in Figure ti . If you look at the soil through I ' will ( ind particles of sand . bits oi clay . pit ' ul plants . It you squeeze the soil . you might force out a few drops of water . A sample of soil from different place probably wont contain the same amount of , clay , or water Heterogeneous Mixtures A cam be or homogeneous . In heterogeneous mixture ( het Ur uh the nee us . you can see the different parts . The damp soil described above it one of mixture . So is a salad . think of how ca ' is to we the pieces , tomatoes , uL ) and other that cooks put together in countless ' a ) and amounts . Homogeneous Mixtures The ( in homogeneous mixture ( huh muh . us ) are so evenly mixed that you can see the different parts . Suppose you stir a teaspoon of sugar into glass of water stirring , for a little while . the , and you can no longer we crystals of sugar in the water . You know the sugar is there . though , because the sugar solution tastes sweet , A solution is an example of a homogeneous mixture . A solution docs not have to be a liquid . however . is a solution of nitrogen gas ( and oxygen gas ( plus small amounts ota few other gases . A solution can even be solid . Brass is a solution of the ( copper and . Homogeneous A swimmer blows bubbles of a homogeneous mixture of gases . I Heterogeneous Mixture Soil a flowerpot in your home may be very different from the soil in a nearby park . Interpreting Photographs What tells you that the soil is a heterogeneous mixture ?

hunter 65 Form 10 Separating a Mixture The properties of iron , sulfur , and table salt help in separating a mixture of these substances . Iron is removed when a magnet attracts the Iron . Mixture Iron . sulfur . and table salt compose a mixture . Using a Magnet Video Held Trig ) Introduction to Matter 660 The is isolated when it is trapped in the filter paper . Water is added , dissolving the salt but not the sulfur . Filtering the Mixture Separating Mixtures Compounds and mixtures differ in yet another . A compound can difficult in separate into its . But . an is easy to separate into its because each component keeps ils proper ties . Figure ) illustrates few of the ways you can use the properties of to them . These methods include . and . In the . filings . and table salt start of ?

mixed in pile . Iron is attracted to a magnet . while sulfur and salt arc nut . Salt can be dissolved in water . but sulfur will not dissolve . So . pouring mixture of salt , sulfur . and water through paper removes the sulfur . the remaining solution can be distilled . In distillation . a liquid solution is boiled . of the mixture that have boiling will boil away al different . As most 01 the water boils in Figure it is cooled and then collected in . Once the remaining salt water is allowed to dry . or evaporate . only the salt is left .

When the salt water is boiled , very salty water is left behind in ' wam The mixture cools Inside has been the tube . separated The very salty into its water is poured components Water id into a beaker the vapor . water evaporates , i We ask leaving the salt on , behind . Table salt Sulfur a Liquid Solution Evaporation section Vocabulary Skill I low does . Identifying How does a heterogeneous HUT the meaning of the lu ' and homo help mixture differ a mixture ?

you remember the Key Terms . Drawing Why is it correct to say and ?

that seawater is a mixture ?

Solving you stir a little baking soda into water until the water looks clear again . How could you prove to someone Reviewing Key Concepts . I . Explaining What is the difference between Chemical i and Physical ?

that the clear material is solution . not . Classifying A metal melt . Is this ?

property ofthe ( as chemical or physical ?

Explain your choice . man ! Making Judgments Helium does not lead with any other substance . in it accurate to say ia has no Chemical ?

Ratios Look at the following chemical ' HO I a . Reviewing Huw are elements and , as compounds similar ?

How do ?

Applying Concepts Plants make a sugar with formula What make up this compound ?

Standards What is a physical change ?

What is a chemical change ?

Changes in Matter Students know the Idea of NEW Substance Formed ?

535 ! I ' I . Obtain a piece of chalk about the size of a pea . Observe it number of atoms stays the same no rem ! mam , On a piece of clean paper , crush the piece of chalk with the their total mass my the same . back of a metal spoon . Describe the changes that occur . Place some of the crushed chalk into the bowl of the spoon . Add about drops of vinegar . Describe what happens . Think it Over Drawing Conclusions Chalk is mostly a single substance , calcium carbonate . Do you think a new substance was formed when the chalk was crushed ?

Do you think a new substance was termed when vinegar was added Provide evidence for your answers . Key Terms physical change I chemical change I law oi conservation of matter You look up from the sand sculpture you your friends have working on all . Storm clouds are gathering . and you know the sand castle may not last long . You pull on to cover start sunburn and begin to pack up . The of storm clouds , the ( lI of sand art , and your sunburn arc of in is about changes in matter . In this section , you will read about some changes . Sand has been transformed Into art .

Physical Change in can matter ?

A physical change is any change that alters the form or ul matter but does not any in the matter into i . lot example . sand artist may change pile ind a . the made ul ' sand . A substance that undergoes a physical change is still the same substance after the change . Changes of Stale ( matter occurs in three , liquid . and gas . Suppose yuu leave small puddle ol liquid water un the kitchen When you come two puddle is . Has the liquid water ?

physical change happened The liquid water water vapor in gas ) and mixed with the air . A change in state , such rum it solid In liquid in ( at liquid to at inn , is an example ulu . Changes in Shape or Form physical change when you teaspoon sugar in ?

he sure . you need to know or not the been changed in . For example . you know that sugar taste weet . just like the singer . you pour the sugar into AI pan and let the water dry nut , the sugar will remain at a crust at the of the pain . The cruel may not look exactly like the before you dissolved it . but it still sugar . 50 , dissolving is . physical changes are bending . breaking . chopping . and the that ( the shape or form of matter . The ( of and di , that you read about in Section also involve changes . Why is the mailing of an in ( uh called a physical , change ?

Fawn 12 Change in Form Crushing aluminum soda can does change the aluminum into another metal ( left ) When table sugar dissolves in a glass of water , it is still sugar ( light ) FIGURE 11 Change of State At room temperature , the element iodine is a purple that easily becomes a gas . Classifying Why is the change in the iodine as physical change ?

Table sugar ( Go ' Links on chemical changes Visit sory Web Finns 13 Four examples ol chemical change are listed in the table . Interpreting Photographs What fuel is undergoing combustion in the photograph Combustion Rapid combination of a fuel , Combustion with oxygen produces heat , light . and new substances Use of electricity to break a down Electrolysis compound into elements or water into hydrogen ( at . cam In US my an substance with oxygen fence Slow combination of a bright ol brass metal with sulfur or another Chemical Change A second kind of change occurs when a substance is formed into a different substance . A change in matter that produces one or more new substances is chemical change , ora chemical reaction . In some chemical changes . a single substance simply changes to one or more other . For example , when hydrogen peroxide is poured on a cut on your skin . it breaks down into water and oxygen gas . in other chemical changes . two or more substances bine to different substances . For example , iron metal combines with oxygen from the air to form the substance iron oxide . which you call rust . Unlike a physical change . a chemical change produces new substances with properties different from those of the original substances . Examples of Chemical Change One familiar chemical change is the burning ol natural gas on a gas stove . Natural gas is mostly the compound methane . When it burns . ane combines with oxygen in the air and forms new substances . These new substances include dioxide gas , and water vapor , which mix with air and are carried away . Both of these new substances can be by their ties . which are different front those of the methane . The ical change that occurs when fuels such as natural gas . wood . candle wax . and gasoline burn in air is called . Other processes that result in chemical change include , oxidation . and tarnishing . The table in Figure 13 describes each of these kinds of chemical changes . Examples of Chemical Change Desolation substance . producing a dark coating on the metal

Conservation of Matter A candle may seem to go away II when it is burned . or water may seem to dis when it ! changes to a gas . scientists long ago ?

a ' me . el used In many ranges . wise . In the I a , when bu , no is out in which he made accurate oli mass both and alter a chemical change . data showed that no mass was lost or gained during the change . The fact that matter is not created or destroyed in any chemical or ical change is calla the law of conservation of matter . that mass the amount of matter . So . this law is sometimes called the law of conservation of mass . Suppose you could collect all carbon ( and water produced when burns , and you the ma of all of this matter . You would that it the mass of the original plus the mass of tho oxygen that was used in the burning . mug is lost . during a chemical change . atoms are not lost or gained . for this reaction is shown in Figure IS . Why is as a chemical change ?

Mun 15 , Conserving Matter act The of atoms the law of conservation of matter . For every molecule of For Mam , methane that burns , two molecules at oxygen are used . The atoms are rearranged in the web ( but they do not disappear . Mo oxygen Two molecule molecules I carbon atom carbon atom It hydrogen atoms hydrogen atoms oxygen atoms I oxygen atoms Output ! 671

) Data Is Matter Conserved ?

Propane ( is a fuel that is often used in camping stoves . when propane burns . it reacts with oxygen , producing carbon dioxide gas and water vapor . The data table shows how much carbon dioxide is produced when different amounts of propane burn in oxygen . Interpreting Data Based on the data in the table , how do you know that carbon dioxide is not the only substance formed in this chemical change ?

Calculating Copy the data table and add a new column on the right . In the new column , enter how much water vapor is produced for each amount of propane burned . Section . Graphing Use the data in the table to . Reading Graphs Use the graph to predict Assessment Math Algebra and Equations , at Produced ( make a graph . Plot the mass of , reacted on the horizontal axis , and the mass of ( produced on the vertical axis . how much CO , would be produced it 100 grams oi propane burned in oxygen . leading nu , nu Target Reading Identify Main Ideas Review the text about uf Matter on page . Identify or three details that support the main idea that matter is . Reviewing Key Concepts i a . Listing Identify three different kinds of i physical change that could happen to a plastic spoon . Explaining Why is the boiling of water considered at physical change ?

Making Which processes is not physical change drying wet clothes . cutting ( ai ( out of paper . lighting a match from a ?

What evidence would you for to whether it change has occurred ?

HINT Applying Concepts Why is the of water as ii chemical change but the freezing of water is not ?

Problem Solving Explain why the mass of nail would be greater than the mass of the nail before it rusted . Assume that all the rust is still attached to the nail . Him The nail rusts when exposed to the air . Writing in Science Persuasive latter Write it letter to persuade a of necessarily mean theta chemical change has occurred .

Standards Focus Students know chemical usually liberate heat or absorb heat , What are some forms ol energy that are related to ( hinges in matter ?

How is chemical energy related to chemical ( hinge ?

Key Terms energy temperature I energy change I change energy energy I energy Energy and Matter Where Was the Energy ?

Add 20 of tap water to an empty soda ( an Measure the temperature of the water with a thermometer ( Hint ' the can about 45 degrees to ( over the bulb of the thermometer with water . Bend a paper clip into the shape shown in the photograph . Stick a small ball of modeling ( lay into the center of an aluminum pie pan . Then stick the straight end of the paper dip Into the ball , Place one marshmallow on the flat surface formed by the top of the paper ( lip , Light the marshmallow with a match . Use tongs to hold the can about over the burning marshmallow until the flame goes out . Measure the water temperature . Think It Over Drawing ' How can you account for any hange in the water temperature ?

What of a ( hange did you observe Du you as if you are lull ol energy ?

Energy is the ability to do work or cause change . livery or change in matter includes change in energy . A change as as . I ' clip ' energy . In liquid water , it ! a the . When candle wax burns . it ' Ill , is ' or ( in chemical . Energy can only he ( is , limit one form In . charcoal burns . minus energy in the forms of heat and light . Chapter ) 73

Flow at Energy Thermal energy from a hot cup at cocoa can warm ( old hands on a chilly day . Developing Hypotheses How will the flow of thermal energy affect the cocoa ?

Flat ) 17 An Endothermic Change An iceberg melting in the ocean absorbs thermal energy from the surrounding water . Forms of Energy How do you know when has ?

You might think that a has energy because it keeps a wristwatch working . And you would be right . Maybe you would think that the sun has energy because it gives off light . Again you would be right . Energy is all around you , and it comes in many forms . of energy related to changes in matter include thermal energy , chemical energy , electromagnetic energy , and electrical energy Thermal Energy Think of how it feels when you walk inside an building from the outdoors on a hot day . Did you exclaim about the change in temperature ?

Temperature is a measure of average energy of random motion of particles of matter . The particles of gas in the warm outside air have average energy of motion than the in the cool building . Thermal energy is the total energy of all of ' particles in an object . Most often . you experience thermal energy when you describe as air in a hot or cold . Temperature and energy are not the same thing . but temperature is related to the amount of thermal energy an object has . Thermal energy always from warmer matter to cooler matter . matter changes . the most common form energy released or absorbed is thermal . For example . absorbs thermal energy from its surroundings when it That why you can pack food and drinks in an picnic to cold . The inciting of ice is an endothermic change . a change in which energy is taken in . Changes in matter can also occur when energy is given off An change energy Combustion is a chemical change that releases energy in the form of heat and light You taken advantage of an mic change if you vu your hands at wood .

Reviewing Math Algebra and Functions Data Comparing Energy Changes A student observes two different chemical reactions , one in beaker A and the other in beaker . The student measures the temperature ' A of each reaction every minute . The student then , plots the time and temperature data and creates ' the following graph . Reading Graphs What do the numbers on the tell you about the length of the experiment ?

Comparing and Contrasting How did the change in temperature in beaker differ from . that in beaker A ?

Interpreting Data which reaction is exothermic ?

Explain your reasoning , I lo . Calculating Which reaction results in a greater ( change in temperature over time ?

Chemical Energy The energy stored in the chemical bonds between atoms is a form of energy called chemical energy . Chemical energy is stored in the foods you eat , in the gasoline used to fuel cars , and even in the cells of your body . When a chemical change occurs . chemical bonds are and new bonds are formed . If change is . some of the chemical energy is transformed and released in a . variety of other . Chemical changes usually involve formations chemical energy and thermal energy . For example . when a match bums . some of the chemical energy contained in the compounds of the match is transformed into thermal energy . inJ Where is chemical energy stored ?

18 Chemical Energy The particles in these grapes contain chemical energy . Your body can use this energy after you eat them .

, For Links on matter and energy Visit Web haunt ' Electrolysis of Water Electrical energy can be used to break down water . into its elements . Bubbles of oxygen gas and hydrogen gas form at separate electrodes . Drawing Conclusions Why is the volume of hydrogen formed twice that of oxygen ?

Hydrogen gas 76 Electromagnetic Energy You probably know that energy reaches Earth in the form of sunlight . Energy front the sun can increase the temperature of the surface of a sidewalk or change your skin by burning it . Visible light is one example of electromagnetic energy ( or electromagnetic radiation ) at of energy that travels through space as waves . Radio waves , infrared rays from heat lamps . the waves that heat food in a microwave oven , ultraviolet rays , and are other types of electromagnetic energy . Chemical changes can give electromagnetic energy . such as the light front a wood . Also , both chemical and physical changes in matter may be caused by electromagnetic energy . For example . a microwave oven can change a block of spaghetti and sauce into a hot me physical change . what is energy ! Electrical Energy Recall from Section I that an atom of a positively charged nucleus surrounded by a negatively charged cloud This cloud moving , negatively charged particles called electrons . Electrical energy is the energy of electrically charged particles moving from one place to another . Electrons more from one atom to another in many chemical changes . chemical change you first read about in Section electrical energy . 111 electrolysis . two metal strips called electrodes are placed in a tion . but the electrodes do not touch . Each electrode is attached to a wire . The wires are connected to at source of electrical energy . such as a battery . As electric current flows through the wires , atoms of one kind lose electrons at one electrode in the tion . At the other electrode . atoms of at ferent kind gain electrons . New substances form at both of the electrodes as a result . Oxygen gas

Transforming Energy The of at fuel is a that and releases it as energy and energy . When you push hike ( and yourself ) up a hill . chemical energy from foods you are is into energy tit . Similarly , other forms tit energy can he , or , into energy . During chemical change , chemical energy may be changed to other for of energy . Other forms of energy may also be changed to chemical energy . One of the energy on Earth that energy is . ing photosynthesis , plants transform energy from the sun into chemical energy as they make molecules of sugar . plants . with animals and other living things that all plants . this chemical energy once again . It the energy needed to carry out life ties . The you have for supply the energy you need to go for walk or read this book . What type or energy occurs during photosynthesis ?

Assessment Section Vocabulary Skill Lise what ) about the and ' to explain the difference between and . Reviewing Key Concepts um MINT ti a . Listing What are ( to changes in ?

Explaining What is ?

How can you tell whether one glass has more thermal energy than . identical glass ul ' Inferring How might you cause an change to and keep ?

Reviewing What to ( energy during chemical ?

Relating Cause and Effect What are the two main of energy given when paper hunts . and where the energy conic ?

Sequencing Describe the link to your ability to turn a page in this hook . 333 Photosynthesis Photosynthesis is a series or chemical changes in which plants convert electromagnetic energy from the sun lnto chemical ' Reading . Maui Tracking Energy Changes Volunteer to help cook a meal tor your family . As you work , point out energy transformations , especially those that involve chemical energy . Explain to a member what chemical energy is and what other terms of energy it can be changed into . Talk about energy sources for cooking and other tools and appliances used to prepare food . Try to identify foods that change chemically when they are cooked . Chapter 17

Isolating Copper by Electrolysis Problem How can electrical energy be used to isolate copper metal ?

Skills Focus making models , inferring , observing , interpreting data . Repeat Step I with another paper clip so that the paper clips are about apart . The , am , 250 paper clips serve as your electrodes . I two metal paper clips . Pour enough copper chloride ( even battery tion into a jar to cover at least half the index card length of the paper clips when the index I wires with alligator clips or a battery holder card is set on top of the jar . CAUTION with wires per chloride solution can be irritating to the copper chloride solution ( 100 skin and eyes . Do not touch it with your hands or get it into your mouth . The solution Procedure can stain skin and clothes . dip and may a hook snap . Place the index card on top of the jar . If the as shown in the diagram . Push the long end 07 19 ' through an index card until the hook just at least half covered by the copper chloride touches the card . solution , add more solution . Attach a wire to one pole of a battery . Attach a second wire to the other pole . Attach each of the other ends of the wires to a separate paper clip , as shown ! the diagram . Do not allow the paper clips to touch one another . Predict what you think will happen if you allow the setup to run for to minutes . Hint What elements are present in the per chloride solution ?

Let the setup run tor to minutes or until you see a deposit forming on one of the . Also look lor bubbles . I . Disconnect the wires from both the battery and the paper clips . Bring your close to the jar and gently wave your hand toward your nose . Note any odor .

, Note whether the color of the solution has . Inferring Based on your observations , does since you began the procedure . electrolysis produce a chemical change ?

10 . Note the color of the ends of the electrodes . i . Write a paragraph ing what you think happened to the copper chloride solution as the electric current flowed through it . 11 . Discard the solution as directed by your teacher , and wash your hands . Analyze and Conclude . Making Models Make a labeled diagram of Design an Experiment your laboratory setup . Indicate which trode is connected to the positive ) side of the battery and which is connected to the What do you think would happen if you switched the connections to the battery without side disturbing the rest of the equipment ?

Design an experiment to answer this question . Obtain your . Inferring Based on your observations , what , before ( substances do you think were produced at , the electrodes ?

On which electrode was each substance produced ?

Recall that one of the substances was a solid you could see and the other was a gas you could smell . Observing Compare the properties of the substances produced to those of the copper chloride in solution . Interpreting Data If the color of the solution changed . how can you explain the change

i ' Study Guide is the study of the properties ol and how matter changes ' Describing Matter ?

Key Concepts ( EV COME ?

at ) um . in mall and ( Include . II are the . IIn ( of . I are ' combined , they ( rum uf ' Key Terms huh ' in , of no ! HI AL ! Key terms , uh i , bum ! Changes in Matter Key ( 351 I A that ' i is . mu . Unlike . from those or the original substances . Key . law or ?

BOO Review and Assessment Go KI For Visit Web ( ode ( Target Reading Skill identify Main Idea Review on Energy and Matter . Tim ) the nI ' in right . Mam Idea Energy carries in many forms Reviewing Key Terms Choose the letter of the best answer . Complete the sentences so that ' I . Thu ability to ' in and lo ym ea phi me key are ( ii . The pencil yuu write with is an uf ?

matter , whi ( it anything that . Ul . an iv ! by their ' chemical properties . in properties that ' I . Water is an ni . All is made up more than ?

different elements . which are pure ' that ' i . lil mall ?

law of Turin uf released or min electrical energy . 10 . The melting ! ice is an at endothermic chan at a lull in whi ' HINT energy . arr always when a a . in . in Science . In . Paragraph Suppose you are preparing for a long journey on the ocean or . Write a journal entry that describes I . I . hem your plan for having fresh , drinkable water oi . unred in the bonds between atoms . ni moving . that travels through space as . throughout your entire trip . Introduction to Matter Chapter !

Review and Assessment Checking Concepts 11 . What are three watts that and mi differ ?

12 . How docs ( hangs differ from clunge ?

13 . How are changes in to changes in ?

14 . How do you know that the candle wax is an exothermic ?

Thinking Critically 15 . Classifying following is pure ' milk in a bowl ?

how you know . 16 . Problem Solving you ' mine sail in glass of water . you prove to ( was . not el chemical change ?

17 . Interpreting Graphs student has two liquids ! same . liquids react with one ' when mixed . The graph the change in alter the two liquids are . Did the energy ?

your answer . Reaction Temperature Time 28 an . 319 Math Practice 18 . Ratios The elements and oxygen form El with fUl ' What is the ratio ul alums lu in the ?

Applying Skills Use the information and the diagrams below to answer Questions it kind all . mi . Hulls ' calm ' IH the kind . 19 . Interpreting Diagrams A single element ?

classifying , pure ' 21 . Interpreting Data the molecules in diagram dill thin in I ) 22 . Interpreting Diagrams Which represents a ?

Standards Investigation Performance Assessment ( the changes you in your lay , with those of . Defend your opinions AIS to or not your physical ur chemical changes .

' Standards Practice Choose the letter of the best answer . What is the best title for the chart below ?

A Chemical Properties of Some Compounds I Physical of Some Elements The Periodic Table of the Gases Found in Air Helium Colorless less dense than air Iron to a magnet melting point of ' Odorless gas at room temperature Oxygen A scientist did an experiment . described by the words and symbols below . Use the information to answer Questions to hydrogen oxygen energy . The scientist Found that grams of ' hydrogen reacted completely with grams of oxygen , What was the total mass of water ?

A grams It ! grams I 14 grams 32 grams . The properties of the water produced by the reaction are A from the properties of both and . the same as the properties hydrogen and oxygen . the same as the properties of . hut from the properties . the same as the . but from the properties of hydrogen . Which pair of terms best the type of change that occurred in the reaction ?

A chemical and chemical and endothermic ( physical and exothermic physical and endothermic Success if Oran at The fact that matter in neither created not destroyed in any chemical or physical change is called the A law of change . law of endothermic change . law of thermal change . law of conservation of matter . How would you classify the buming of natural gas ?

A exothermic chemical change endothermic chemical change exothermic physical change endothermic physical change . Which diagram best represents a mixture of two kinds molecules ?

of ! Water is a compound with the chemical . Compare a physical change involving water with a chemical change involving water . How do differ ?

Chapter ! 003