Issues and Physical Science, 2nd Edition - Lab Aids Act 15-17... · Section Preview of the...

Section Preview of the Teacher’s Edition for

The Chemistry of Materials, Issues and Physical Science, 2nd Edition

Activities 15-17

Suggested student responses and answer keys have been blocked

out so that web-savvy students do not find this page and have access to answers.

To experience a complete activity please request a sample found in the footer at lab-aids.com

240- to 50-minute sessi

ons

B-39

ACTIVITY OVERVIEW

Students compare physical and chemical properties of 13 elements and sort theminto groups based on common properties. They then compare their classificationswith groups—or families—of elements as defined by scientists and displayed in thePeriodic Table of the Elements.

KEY CONCEPTS AND PROCESS SKILLS

(with correlation to NSE 5–8 Content Standards)

1. Elements have characteristic physical and chemical properties. Substances oftenare placed in categories or groups if they react in similar ways; metals are anexample of such a group. (PhysSci: 1)

2. Scientists classify elements into families, based on their properties. (PhysSci: 1)

3. Students develop descriptions based on evidence. (Inquiry: 1)

KEY VOCABULARYatom

atomic mass

element

family (of elements)

metal

Periodic Table of the Elements

15Families of Elements

INVEST IGAT

ION

MATERIALS AND ADVANCE PREPARATION

For the teacher

aluminum, iron, copper, and carbon samples from Activity 14, “Physical and Chemical Properties of Materials”

1 Transparency 15.1, “Information on Element Cards”

8 sets of 4 Element Family Cards

1 transparency of Student Sheet 16.1, “Periodic Table of the Elements”

* 1 overhead projector

* various samples of elements, such as sulfur, silver, and tin (optional)

1 Scoring Guide: UNDERSTANDING CONCEPTS (UC) and/or

1 Scoring Guide: GROUP INTERACTION (GI)

For each group of four students

1 set of 14 Element Cards

* 4 half-sheets of paper of various colors

* chart paper (optional)

* markers (optional)

For each student

1 copy of Scoring Guide: UNDERSTANDING CONCEPTS (UC) (optional)

1 copy of Scoring Guide: GROUP INTERACTION (GI) (optional)

1 copy of Group Interaction Student Sheet 2, “Developing Communication Skills”

*Not supplied in kit

You may wish to collect samples of elements such as sulfur, silver, and tin for display inTeaching Suggestion 1.

Prepare the half-sheets of paper. Students will place the Element Cards on these inTeaching Suggestion 2 as they group them according to physical and chemical prop-erties. In Teaching Suggestion 2, consider asking groups to write their sorts on chartpaper for display around the classroom.

Group Interaction Sheets are in Teacher Resources II: Diverse Learners. Masters forScoring Guides are in Teacher Resources III: Assessment.

Activity 15 • Families of Elements

B-40

Families of Elements • Activity 15

B-41

TEACHING SUMMARYGetting Started

1. Introduce elements as the building blocks of matter.

Doing the Activity

2. (GI ASSESSMENT) Students sort elements based on characteristic physical andchemical properties.

Follow-Up

3. Introduce the the Periodic Table of the Elements.

4. (UC ASSESSMENT) Students compare classification systems and examine the periodic table.if this works)

BACKGROUND INFORMATIONProperties of the Elements

The Element Cards contain information about fourteen of the more simple elements(lowest atomic number and weight) from four columns on the periodic table. Theproperties chosen for the element cards are both physical and chemical. Atomic num-bers are not included because this property of the elements, which depends on thenumber of protons in an atom of the element, was not known to the Russian scientistDmitri Mendeleev when he grouped the elements to create the first periodic table.Were this information included on the cards, students would be likely to use it to sortthe elements, rather than looking at the other properties. Students can usually bestconceptualize the significance of the atomic number when they are introduced to thesubatomic particles in the atom at the high school level.

Atomic mass is a physical property, but it is difficult for students to understand theidea of a particle of such small mass. The atomic masses given on the periodic tableare relative masses based on the mass of carbon 12, which is defined as exactly 12.00.The atomic masses on the periodic table also take into account the abundance of dif-ferent isotopes of an element. Isotopes have various numbers of neutrons, and are notdiscussed in the student materials. The atomic masses given on the Element Cards arethe most common isotopes rounded to the nearest whole number. These are techni-cally called mass numbers.


B-42

TEACHING SUGGESTIONS

GETTING STARTED

1. Introduce elements as the building blocksof matter.

Remind students that in the last activity, theygrouped materials and sorted them into categoriesbased on their properties. Tell them that efforts ofscientists and philosophers to classify matter go farback in history. More than 2,000 years ago, theGreeks introduced the idea that there were somebasic building blocks of matter, called elements.Today‘s scientists know that there are 90 naturallyoccurring elements—substances that cannot be bro-ken down by any normal chemical means, such asheating, reacting them with acids or other chemi-cals, or exposing them to electrical currents. Eachvisible sample of an element is made of many bil-lions of small particles called atoms. Introduce theidea that each kind of element is made of a particu-lar kind of atom. One way in which the atoms varyis in their mass. Students will learn more aboutatoms in Activities 16–19.

Display the aluminum, iron, copper, and carbonsamples from Activity 14, “Physical and ChemicalProperties of Substances.” Tell students that, of thematerials they tested in Activity 14, these four areelements. In fact, they were among some of the firstelements early scientists identified. You may wish todisplay any other element samples you have.

Tell students that in this activity, they will view dataon 14 elements and investigate how these can bedivided into subgroups based on their properties.

DOING THE ACTIVITY

2. (GI ASSESSMENT) Students sort elementsbased on characteristic physical andchemical properties.

Have students read the introduction and Chal-lenge. Review the definition of an element, a sub-stance that cannot be broken down into simplersubstances by heating it or causing it to react withother chemicals. Project Transparency 15.1, “Infor-mation on Element Cards,” and explain the infor-

mation shown on each card. If necessary review thedistinction between chemical and physical proper-ties, as both are included on the Element Cards. Dis-tribute the Element Cards.

Make sure students understand that each cardbegins with the one- or two-letter symbol for eachelement and its name. Next come two physicalproperties: whether the element is metal or non-metal, and is a solid, liquid, or gas at room temper-ature. The next line tells the color of the mostcommon form(s) of the element. The atomic massrefers to the mass of one atom (the smallest bit ofeach element) as based on hydrogen, which has thelightest atom of all the elements. Hydrogen’satomic mass is 1, and the masses of the other atomsare expressed as multiples of the mass of hydrogen.

To further explain the concept of atomic mass, tellstudents that scientists have been able to figure outthe mass of each type of atom, even though theycan’t weigh them directly. Point out that there areno units given on the cards: atomic masses aregiven in relative units called atomic mass units(amu). This is because atoms are so extremelysmall that it doesn’t make sense to express theirmasses in grams, or even milligrams or micro-grams.

The last two lines refer to chemical properties. Reac-tivity refers to how likely the element is to interactchemically, or react, with other elements. Studentsmay know, for example, that pure oxygen is veryreactive, so its reactivity is listed as high. The lastline shows the number of bonds to hydrogen. Thereason for using the formula with hydrogen on thecards, rather than some other element, is that it isthe simplest element and can only make one bond.Students are likely to know that oxygen and hydro-gen are the elements in water: H2O. This formula isbased on the fact that oxygen bonds to two hydro-gens, as noted on the oxygen Element Card.

Distribute the element cards. Have student groupscomplete the Procedure. Before they begin working,consider incorporating some of the sentencestarters from Group Interaction Student Sheet 2,“Developing Communication Skills.” Encourage


B-43

them to use these as they work. Consider providingfeedback on student work using the GROUP INTERAC-TION (GI) Scoring Guide. Groups should worktogether to organize the various Element Cards andrecord the groupings they have formed. Their goalis to form at least three categories, with two similarcharacteristics within each. Most importantly, stu-dents should record the characteristics they chosefor forming each of the categories. If students arehaving problems, suggest that they choose only onecriterion to begin their sorting, but allow them towork as independently as possible. Students arelikely to sort the elements based on the number ofbonds each forms with hydrogen, the state at roomtemperature, and the element’s reactivity.

For Procedure Step 5, hold a brief class discussionabout how students classified the elements. Allowmembers of each group to briefly show their systemand describe the choices they made. You could alsoprovide chart paper and markers for students to dis-play their systems. Highlight the similarities anddifferences between the systems that the studentgroups used by listing them on the board or over-head.

n Teacher’s Note: Students are likely to grouphydrogen with the Halogen Family of Elementsbased on the physical and chemical properties ofhydrogen shown on its element card. This is a rea-sonable classification with the information they areprovided. Scientists also incorporate informationabout valence electrons when grouping elements.For this reason hydrogen is placed on top of Group 1because it has one valence electron in an s orbital,similar to the other elements of Group 1. This infor-mation is beyond the scope of this activity, but willbecome apparent when students see the PeriodicTable of Elements in Teaching Step 3.

Do not hand out the sets of Element Family Cards toeach group until Procedure Step 6. Explain that sci-entists look for patterns in their observations anduse the same data students used plus additionaldata to categorize the elements into groups calledfamilies. Students have investigated elements infour families, and now they will compare their clas-

sification schemes to scientists’ schemes. (Note thatthe four family names are not included as keyvocabulary. Students will use them in this activity,but are not expected to memorize them unless thatis a local or state requirement.) The activity stressesthat there are families of elements and that theyare based on chemical and physical properties.Before students begin this step, it may be helpful toreview with them the names and characteristics ofeach family shown on the Element Family Cards.Then hand out the Element Family Cards to eachgroup.

FOLLOW-UP

3. Introduce the Periodic Table of theElements.

Make sure students understand that the cards showonly 14 of the more than 100 known elements. Tellthem that scientists have taken a similar approachto classify and organize all of the elements onto atable called the Periodic Table of the Elements.Explain to students that the categories for the Ele-ment Family Cards are four of the accepted scien-tific classifications. Display the transparency ofStudent Sheet 16.1, “Periodic Table of the Elements,”and point out the four families (alkali metals, alka-line earth metals, halogens, and noble gases)included in this activity. You may want to tell stu-dents that the term noble gases refers to the factthat these elements only very rarely react, or “asso-ciate,” with other elements. They were once calledinert gases, but this name was discarded becausethey do react under some circumstances.

Lead students to notice that the periodic tableorganizes a large number of elements into columnsand rows and provides atomic numbers and atomicmasses for each. Do not go into too much detailnow; the next activity provides more informationabout the periodic table.

Emphasize the importance of systems for classifica-tion and organization, such as the periodic table.They allow scientists to organize and make sense ofvast amounts of data. They also allow scientistsfrom all over the world to communicate with each


B-44

other and exchange information in a common sci-entific vocabulary. As scientists gather more data, aclassification system will develop further. This hashappened with the periodic table: as new elementshave been discovered, new rows have been addedand other modifications have been made.

Discuss some of the additional properties shown onthe Element Family Cards. These include the physi-cal properties of density and melting point and spe-cific examples of chemical reactivity, such as thevigorous reactions of alkali metals with water. Stu-dents can refer to these properties to characterizeelements.

Prompt students to compare their sorts with thePeriodic Table of Elements shown on the trans-parency of Student Sheet 16.1. Ask them to identifysimilarities between their sorts and the acceptedconvention of sorting the elements as shown in thePeriodic Table.

4. (UC ASSESSMENT) Students compareclassification systems and examine theperiodic table.

You may score Analysis Question 5 with the UNDER-STANDING CONCEPTS (UC) Scoring Guide to assesswhether students understand the main idea of theactivity. Here students must apply the characteris-tics of a family to an additional element—stron-tium. This element is in the same family as calciumand magnesium, so students should predict that itis likely to be a solid, silvery white metal that makestwo bonds with hydrogen. Its reactivity is likely tobe very high, since it is closer to calcium than mag-nesium. Students who look closely should predict amass greater than 80, since they would see that theelement will come after bromine, which has a massof 80.

Analysis Question 5 focuses on the characteristics ofthe families. Review with your students your expec-tations for their responses, and let them know thatyou will use the UC Scoring Guide to give them feed-back. If appropriate, distribute copies of the UCScoring Guide to students. For more informationabout scoring guides, see Teacher Resources III:Assessment.

SUGGESTED ANSWERS TO QUESTIONS

1. Which of the properties listed on the Element Cards

are:

a. physical properties?

The color, atomic mass, whether the sub-stance is a metal or nonmetal, and whether itis solid, liquid, or gas are physical properties.

b. chemical properties?

The substance’s reactivity and number ofbonds with hydrogen are chemical proper-ties because they involve reactions with othersubstances.

2. How did your first classification system

compare to the second classification with

the Element Family Cards?

Answers will vary, and should be based on stu-dents’ recognition of differences between theirsystems and the system provided on the ElementFamily Cards. For example, students may haveput all gases together, divided the materials intoonly two groups (metals and nonmetals), or putthe alkaline earth metals with the halogensbecause both groups bond with one hydrogen.

3. In what ways could grouping elements help scientists understand their properties?

Grouping elements into families helps scientistsbecause they can remember the properties of afew families, rather than for each separate ele-ment, and because it helps them to organize alarge amount of data. They can then look forcomparisons within and between groups.

4. Use the table of elements you constructed to find the

family or families of elements that are:

a. not usually reactive. noble gases

b. highly reactive. alkali metals, halogens (alkaline earth metals are also acceptable)

c. all metals. alkali metals and alkalineearth metals

d. all solids. alkali metals and alkalineearth metals

e. all gases. noble gases

Sample responses removed for preview


B-45

5. (UC ASSESSMENT) The element strontium (Sr) is

below calcium (Ca) in Column 2 on the periodic

table. Design an Element Card that shows the prop-

erties you predict for strontium.

Sr

Strontium

metal

solid

silvery white

Atomic mass: over 80

reactivity: high

# of bonds to hydrogen: 2

Issues and Physical Science • Transparency 15.1

©20

15 T

he R

egen

ts o

f th

e U

nive

rsity

of

Cal

iforn

ia

B-47

Information on Element Cards

HHydrogen

non-metalgascolorlessAtomic mass: 1Reactivity: highNumber of bonds to hydrogen: 1

Element symbolElement name

Chemical characteristics

Physical characteristics

TEACHER RESOURCES • ASSESSMENT III

123

Scoring GuideLEVEL DESCRIPTION

Level 4 Above and beyond

Student accomplishes Level 3 AND goes beyond in some significant way, such as: • using relevant information not provided in

class to elaborate on your responsee. • using a diagram to clarify scientific concepts. • relating the response to other scientific

concepts.

Level 3Complete and correct

Student accurately and completely explains or uses relevant scientific concepts.

Level 2Almost there

Student explains or uses scientific concepts BUT has some omissions or errors.

Level 1On your way

Student incorrectly explains or uses scientific concepts.

Level 0 Student’s response is missing, illegible, or irrelevant.

X Student had no opportunity to respond.

4. UNDERSTANDING CONCEPTS (UC)

What to look for: • Student’s response identifies and describes scientific concepts relevant to a particular

problem or issue.

ISSUES AND PHYSICAL SCIENCE

126

9. GROUP INTERACTION (GI)

What to look for: • Group members work together as a team and the ideas of all members were valued

and weighed in working toward the common goal.



Group members accomplish Level 3 and go beyond in some significant way, such as: • actively asking questions about each others’

ideas. • actively helping each other accomplish the

task. • building on each other’s ideas.


All group members participate and respectfully consider each others’ ideas.

Level 2Almost there

Unequal group participationOR group respectfully considered some, but not all, ideas.

Level 1On your way

Significantly unequal group participationOR group totally disregarded some members’ comments and ideas.

Level 0 Members do not work togetherOR single individual does entire task.


COMMUNICATING SENTENCE STARTERS

To better understand One point that was not clear to me was . . . Are you saying that . . . Can you please clarify . . .

To share an idea Another idea is to . . . What if we tried . . . I have an idea. We could try . . .

To disagree I see your point, but what about . . . Another way of looking at it is . . . I’m still not convinced that . . .

To challenge How did you reach the conclusion that . . . What makes you think that . . . How does it explain . . .

To look for feedback What would help me improve . . . Does it make sense, what I said about . . .

To provide positive feedback One strength of your idea is . . . Your idea is good because . . .

To provide constructive feedback

The argument would be stronger if . . . Another way to do it would be . . . What if you said it like this . . .

Developing Communication Skills

©20

15 T

he R

egen

ts o

f the

Uni

vers

ity o

f Cal

iforn

ia

ISSUES AND PHYSICAL SCIENCE GROUP INTERACTION STUDENT SHEET 2

NAME ___________________________________________________________________________________ DATE __________________________


ons

B-49

ACTIVITY OVERVIEW

Students read about the history and organization of the Periodic Table of the Ele-ments and are introduced to the difference between elements and compounds. Thereading also introduces atoms, molecules, and chemical formulas. Students use theStopping to Think literacy strategy while reading to improve their reading compre-hension.



1. Elements do not break down under ordinary laboratory reactions involving suchtreatments as heating, exposure to electrical current, or reaction with acids.(PhysSci: 1)

2. There are more than 115 chemical elements that combine in a multitude of waysto produce compounds. (PhysSci: 1)

3. Elements combine with each other in characteristic ways to form new substances(compounds) with different characteristic properties. (PhysSci: 1)

4. Substances are often placed in categories or groups if they have similar proper-ties. Metals are an example of such a group. (PhysSci: 1)

5. Scientists communicate their findings and build on each other’s work. (HistSci: 2, 3)

6. Studying Mendeleev provides insights into scientific inquiry and the nature ofscience. (HistSci: 3)

KEY VOCABULARYatom

atomic mass

chemical formula

compound

element

family

molecule

16Elements and the Periodic Table

READIN

G


For the teacher


* 4 different colored transparency markers (optional)

For each group of four students

1 set of 4 Element Family Cards (optional for Getting Started review)

For each student

1 Student Sheet 16.1, “Periodic Table of the Elements”



1. Review element families and the Periodic Table of the Elements.

Doing the Activity

2. (LITERACY) Students read the text and answer Stopping to Think questions.

Follow-Up

3. (UC ASSESSMENT) The class applies concepts from the reading to their use of theperiodic table and chemical formulas.

BACKGROUND INFORMATIONThe Elements

Elements 1 (hydrogen) through 92 (uranium) are generally referred to as the naturalelements, although two of these elements—43 (technetium) and 84 (polonium)—arenot actually found naturally on earth. Elements 43, 84, and all elements beyond 92are referred to as artificial, or synthetic, elements. They have been produced throughnuclear reactions in laboratory settings. Since nuclear reactions are generally a partof high school science curriculum, this course focuses on the 90 natural elements thatare the building blocks for matter on earth. At the time of this writing, elements 93through 111 have been verified by the International Union of Pure and AppliedChemistry (IUPAC) and named by the laboratories that first synthesized them. Evi-dence for the synthesis of elements 112, 113, 114, 115, 116, and 118 has also beenreported, and it is expected that most or all of these will eventually be verified byIUPAC. Since the status of these elements makes it difficult to give an exact number,we indicate in the student materials that more than 115 elements are known. Recentversions of the periodic table differ slightly depending on what reports of elementsthey choose to accept. Although additional elements may be synthesized in nuclearlaboratories, the basic number of elements found naturally stays the same.

Activity 16 • Elements and the Periodic Table

B-50

Elements and the Periodic Table • Activity 16

B-51

When two or more elements are held together by chemical forces, or bonds, they forma compound. These bonds can be ionic, which occurs when electrons are transferredfrom one atom to another, or covalent, which occurs when atoms share electrons.Compounds have none of the characteristics of the original elements. Hydrogen (H)for example is a colorless, odorless gas that is very light and highly explosive when itmeets air, and oxygen (O) is also a clear, colorless gas that is very flammable. How-ever, when these two elements bond and form a molecule, that compound is a non-flammable liquid—water (H2O). Water illustrates another defining characteristic ofcompounds: the elements in a compound are in a fixed ratio. In water this ratio is 2hydrogens to 1 oxygen, as expressed in the formula H2O. Water cannot be separatedinto hydrogen and oxygen by physical methods—only a chemical reaction can sepa-rate it.

Mixtures are combinations of two or more substances (elements and/or compounds)that are held together by physical forces. They can be separated by physical methods,such as filtering or evaporation. A solution of solids in water, for example, is a mix-ture. In a saltwater solution, the water can be evaporated, leaving the salt. The ratioof substances in a mixture can vary greatly because they are not chemically bondedand can combine in various proportions.

n Teacher’s Note: This activity continues a discussion on the nature of elements,atoms, compounds, molecules, and mixtures to build students’ understanding of theParticulate Theory of Matter. Understand that the treatment of these topics in thisunit is very basic and does not explore ions and subatomic particles. This will be takeplace in greater detail in Unit C, “Water,” of Issues and Physical Science.


B-52


GETTING STARTED

1. Review element families and the PeriodicTable of the Elements.

Review the four chemical families thatstudents explored in Activity 15, “Fami-lies of Elements.” To each group, pass

out a set of Element Family cards used in Activity 15.Help students locate each of the families on StudentSheet 16.1, “Periodic Table of the Elements.” Youmight also outline each of the four families – alka-line metals, alkaline earth metals, halogens, noblegases – using different colored transparency mark-ers on a transparency of Student Sheet 16.1. Toreview the properties of each group prompt stu-dents with such questions as, Of the four familiesyou investigated, which two seem the most alike?Which one seems most different from the others?What kinds of properties can you use to distinguishgroups of elements? Also review some of the proper-ties used to categorize the elements: such physicalproperties as their color, whether they are metals ornot, whether they are solid, liquid, or gas at roomtemperature; and such chemical properties as theirreactivity and the number of bonds they form withhydrogen.

Point out to students that although color is not acharacteristic of such mixtures as plastic products,which can have coloring agents added, color is acharacteristic of pure elements, such as the charac-teristic yellow of sulfur or the characteristic colors ofcopper and gold.

Have students read the introduction and Chal-lenge. Review, as introduced in Activity 15, “Fami-lies of Elements,” the fact that everything on earthis made of elements, either in pure form or in chem-ical combinations of the elements, which are calledcompounds. Also reiterate that all elements aremade of smaller particles, or bits of matter. Thesmallest particle that is characteristic of an elementis an atom.

DOING THE ACTIVITY

2. (LITERACY) Students read the text andanswer Stopping to Think questions.

This activity is supported by a Directed ActivitiesRelated to Text (DART) strategy called Stopping toThink. The Stopping to Think questions prompt stu-dents to think about what they are reading and insome cases to apply what they have read. Thesequestions do not require a written response, and aredifferent from the Analysis Questions found at theend of the activity. Stopping to Think questions areintended to focus students’ attention on importantideas in the text as they read. They may require stu-dents to identify the main idea of a previous para-graph or to synthesize ideas presented in two ormore preceding paragraphs. Sample responses tothe questions are listed below. For more informa-tion on this strategy, see the Literacy section ofTeacher Resources II: Diverse Learners.

Stopping to Think 1

In what way were the ancient Greek philosophers right

about elements?

The early Greeks were right in that they thoughteverything was made of elements.

In what way were the ancient Greek philosophers

wrong?

They thought the elements were earth, air,water, and fire.

Stopping to Think 2

How did Mendeleev build on other scientists’ work?

He analyzed the data other scientists collectedabout the properties of the 63 elements thatwere known at the time.

How did other scientists build on Mendeleev’s work?

They predicted and found other elements basedon the periodic table and revised the arrange-ment of the table to fit new discoveries. Scientistsstill use the table first arranged by Mendeleev topredict the properties and existence of newlycreated elements.

Sample responses removedfor preview

Elements and the Periodic Table • Activity 16

B-53

Stopping to Think 3

Use the Periodic Table of the Elements on the next page

to decide whether each of the following is a metal or

nonmetal: lithium (Li), carbon (C), sulfur (S), calcium

(Ca), titanium (Ti), and bromine (Br).

Li, metal; C, nonmetal; S, nonmetal; Ca, metal;Ti, metal; Br, nonmetal

Stopping to Think 4

Find magnesium on the periodic table.

What is magnesium’s chemical symbol?

Mg

What family does magnesium belong to?

Group 2, alkaline earth metals.

Is magnesium a solid, a liquid, or a gas?

A solid

Based on its family, would you expect magnesium to be

very reactive, somewhat reactive, or not reactive at all?

Very reactive since it is in the alkaline earthmetal family.

Stopping to Think 5

What are two ways that compounds are different from

the elements that form them?

First, elements are made of one kind of atom,while compounds are made of molecules thatcontain more than one kind of atom. Second,compounds have different chemical and physi-cal properties from the elements that makethem.

Stopping to Think 6

The chemical formula for baking soda is NaHCO3.

What elements are in baking soda? How many of each

type of atom is represented by the formula for baking

soda?

Baking soda contains 1 sodium, 1 hydrogen, 1carbon, and 3 oxygens.

FOLLOW-UP

3. (UC ASSESSMENT) The class applies conceptsfrom the reading to use of the periodictable and chemical formulas.

Begin by discussing what students have learnedabout the organization of the periodic table. Reviewthe symbols and key for the periodic table in theStudent Book. Refer students to Student Sheet 16.1,“Periodic Table of the Elements.” Stress that groupsof similar elements are often found in columns inthe periodic table, and that these comprise familiesin that their physical and chemical properties aresimilar. The Periodic Table of the Elements is behelpful in that it helps to us predict or categorize anelement’s properties based on its position on thetable. Review the changes that take place as you gofrom left to right across the table, from metals tononmetals.

It is key that students understand that the PeriodicTable of Elements is a reference tool used to describeand help understand elements and interactionswith each other. To this end, analysis Question 2emphasizes the difference in properties of the com-pound NaCl (table salt) from its constituent ele-ments, sodium and chlorine. Explain that it is oftenthe case that compounds are not at all like the ele-ments that make them. For example, sugar con-tains: carbon, the solid that forms coal anddiamonds; oxygen, necessary for human respira-tion; and hydrogen, an explosive odorless gas. Yetsugar is a white, crystalline, edible solid. AnalysisQuestion 3 lets students apply information from thereading—that water and salt are compounds—toconclude that seawater must be a mixture.

3Analysis Question 4 is an opportunity to checkstudents’ understanding of the relationshipbetween an atom and a molecule.


B-54


1. Make a copy the table below into your

science notebook. Use the Periodic Table of

Elements to find out which atoms make up a mole-

cule for each of the substances listed. The first row

has been completed for you.

Chemical Formulas of Common Substances

2. Sodium is a metallic solid, and chlorine is a poison-

ous yellow-green gas. Sodium and chlorine react to

form sodium chloride, which is common table salt.

a. Is table salt an element or a compound? Explain.

It is a compound, because it contains morethan one element.

b. Describe the physical properties of table salt.

It is a white solid that you can eat.

c. How do the properties of table salt compare with

those of sodium and chlorine?

They are very different. Table salt has a dif-ferent color from both sodium and chlorine.It is neither a metal nor a gas. Unlike chlo-rine, it isn’t poisonous. And unlike sodium, itdoes not form a corrosive solution in water.

3. Is seawater an element, compound, or mixture?

Explain your answer.

Seawater is a mixture. It contains more than onecompound—water and salt (and other com-pounds, which students may or may not know).

4. Explain the relationship between an atom

and a molecule.

Students’ answers will vary. A correct answerwill explain that molecules are composed of twoor more atoms held together with chemicalbonds.

SubstanceChemical formula

Atoms that makeup the molecule

Water H2O 2 hydrogen atoms1 oxygen atom

Hydrogen peroxide

H2O22 hydrogen atoms2 oxygen atoms

Carbon dioxide

CO21 carbon atom2 oxygen atoms

Sucrose (tablesugar)

C12H22O11

12 carbon atoms22 hydrogen atoms11 oxygen atoms

Alanine (anamino acid)

C3H7O2N

3 carbon atoms7 hydrogen atoms2 oxygen atoms1 nitrogen atom

Oleic acid (a fat)

C12H24O2

12 carbon atoms24 hydrogen atoms2 oxygen atoms

3

Name Date

Issues and Physical Science • Student Sheet 16.1

©20

15 T

he R

egen

ts o

f the

Uni

vers

ity o

f Cal

iforn

ia

B-55

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54Rb

Sr

Y

Zr

N

b M

o Tc

Ru

Rh

Pd

A

g Cd

In

Sn

Sb

Te

I

Xe

rub

idiu

m

stro

ntiu

m

yttr

ium

zir

coni

um

niob

ium

m

olyb

denu

m te

chne

tium

rut

heni

um

rhod

ium

p

alla

dium

sil

ver

cadm

ium

in

dium

tin

an

timon

y te

lluriu

m

iodi

ne

xeno

n85

.47

87.6

2 88

.91

91.2

2 92

.91

95.9

4 (9

8)

101.1

10

2.9

106.

4 10

7.9

112.4

114

.8

118.7

12

1.8

127.6

12

6.9

131.3

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36K

Ca

Sc

Ti

V

Cr

Mn

Fe

Co

Ni

Cu

Zn

Ga

Ge

As

Se

Br

Krp

otas

sium

ca

lcium

sc

andi

um

titan

ium

va

nadi

um

chro

miu

m

man

gane

se

iron

cob

alt

nicke

l co

pp

er

zinc

ga

llium

ge

rman

ium

ar

seni

c se

leniu

m

bro

min

e kr

ypto

n39

.10

40.0

8 44

.96

47.8

7 50

.94

52.0

0 54

.94

55.8

5 58

.93

58.6

9 63

.55

65.3

9 69

.72

72.6

4 74

.92

78.9

6 79

.90

83.8

0

55

56

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86Cs

Ba

Lu

H

f Ta

W

Re

O

s Ir

Pt

A

u H

g Tl

Pb

Bi

Po

A

t Rn

cesi

um

bar

ium

lu

tetiu

m

hafn

ium

ta

ntal

um

tung

sten

rh

eniu

m

osm

ium

iri

dium

p

latin

um

gold

m

ercur

y th

alliu

m

lead

b

ism

uth

pol

oniu

m

asta

tine

rado

n13

2.9

137.

3 17

5.0

178.

5 18

0.9

183.

8 18

6.2

190.

2 19

2.2

195.

1 19

7.0

200.

6 20

4.4

207.2

20

9.0

(209

) (2

10)

(222

)

87

88

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118Fr

Ra

Lr

Rf

D

b Sg

Bh

H

s M

t D

s Rg

Cn

U

ut

Uuq

U

up

Uuh

U

us

Uuo

franc

ium

ra

dium

law

renc

ium

ruth

erford

ium

dub

nium

se

aborg

ium

b

ohriu

m

hass

ium

m

eitn

eriu

m da

rmst

adtiu

m ro

entg

eniu

m co

per

nici

um un

untr

ium

unun

quad

ium

un

unp

entiu

m

unun

hexi

um un

unse

ptiu

m un

unoc

tium

(223

) (2

26)

(262

) (2

67)

(268

) (2

71)

(272

) (2

77)

(276

) (2

81)

(280

) (2

85)

(284

) (2

89)

(288

) (2

93)

( )

(294

)

57

58

59

60

61

62

63

64

65

66

67

68

69

70La

Ce

Pr

N

d Pm

Sm

Eu

G

d Tb

D

y H

o Er

Tm

Y

bla

ntha

num

ce

rium

pras

eody

miu

m ne

odym

ium

pro

met

hium

sam

ariu

m

euro

piu

m

gado

liniu

m

terb

ium

dy

spro

sium

ho

lmiu

m

erb

ium

th

uliu

m

ytte

rbiu

m13

8.9

140.

1 14

0.9

144.

2 (14

5)

150.

4 15

2.0

157.

3 15

8.9

162.

5 16

4.9

167.

3 16

8.9

173.

0

89

90

91

92

93

94

95

96

97

98

99

100

101

102

Ac

Th

Pa

U

Np

Pu

Am

Cm

Bk

Cf

Es

Fm

M

d N

oac

tiniu

m

thor

ium

p

rota

ctin

ium

ur

aniu

m

nep

tuni

um p

luto

nium

am

eric

ium

cu

rium

b

erke

lium

ca

lifor

nium

ei

nste

iniu

m

ferm

ium

m

ende

leviu

m

nob

eliu

m(2

27)

232.

0 23

1.0

238.

0 (2

37)

(244

) (2

43)

(247

) (2

47)

(251

) (2

52)

(257

) (2

58)

(259

)

11 12

13

14

15

16

17

18

Na

Mg

Al

Si

P S

Cl

Ar

sodi

um

mag

nesi

um

alum

inum

si

licon

p

hosp

horu

s su

lfur

chlo

rine

argo

n22

.99

24.3

1

26

.98

28.0

9 30

.97

32.0

7 35

.45

39.9

5

3 4

5 6

7 8

9 10

Li

Be

B C

N

O

F N

elit

hium

b

eryl

lium

b

oron

ca

rbon

ni

troge

n ox

ygen

fl u

orin

e ne

on6.

941

9.01

2

10

.81

12.0

1 14

.01

16.0

0 19

.00

20.182 He

heliu

m4.

003

1 Hhy

drog

en1.0

08

Lanthan

ides

Actinides

Perio

dic

Tabl

e of

the

Ele

men

ts

solid

at ro

om

tem

pera

ture

liqui

d at r

oom

te

mp

eratu

re

gas

at roo

m

tem

pera

ture

A A ASHA

DIN

G K

EY

2

1

3 4

5 6

7 8

9 10

11

12

13

14

15

16

17

18


ons

B-57

ACTIVITY OVERVIEW

Students continue their exploration of the organization of atoms and molecules as they use models to investigate atoms, elements, chemical bonds, molecules, andcompounds.



1. There are more than 115 known elements that react in a multitude of ways to pro-duce compounds, which account for the living and nonliving substances that weencounter. (PhysSci: 1)

2. An element is a substance made up of only a single type of atom. (PhysSci: 1)

3. Molecules are combinations of atoms held together by forces of attraction calledbonds. (PhysSci: 1)

4. A compound is a substance made up of atoms of more than one kind of element,bonded together to form molecules. (PhysSci: 1)

5. Scientists often use models to demonstrate scientific concepts. (Inquiry: 2)

KEY VOCABULARYatom

chemical bond

chemical formula

compound

element

molecule

17Modeling Molecules

MODELIN

G


For the teacher


1 Literacy Transparency 3, “Reading Scientific Procedures”

1 Scoring Guide: UNDERSTANDING CONCEPTS (UC)

* overhead projector

For each pair of students

1 molecular model set containing:

32 white “atoms”

18 black “atoms”

14 red “atoms”

4 blue “atoms”

54 white “bonds”

* 1 set of red, blue, and black pencils (optional)

For each student

1 Student Sheet 16.1, “Periodic Table of the Elements”

1 copy of Scoring Guide: UNDERSTANDING CONCEPTS (UC) (optional)


Provide colored pencils if you would like students to use them when they draw theirmodels of molecules. Prepare Literacy Transparency 3 which can be found in the Literacy section of Teacher Resources II: Diverse Learners.


1. Introduce the molecular model set as a tool for studying atoms and molecules.

Doing the Activity

2. Introduce strategies for reading scientific procedures

3. Students build models of molecules.

Follow-Up

4. (UC ASSESSMENT) The class discusses the principles illustrated by the model-build-ing experience.is)

BACKGROUND INFORMATIONChemical Bonding

In this unit, there is no discussion of subatomic particles and only a brief mention ofthe nucleus, as these concepts are usually taught in depth in high schools. The follow-ing background is provided in case your local standards require you to go into moredepth in middle school.

Activity 17 • Modeling Molecules

B-58

Modeling Molecules • Activity 17

B-59

Atoms consist of a nucleus, which contains positively charged protons and unchargedneutrons, and a cloud of negatively charged electrons. The number of protons is theatomic number and determines the identity of the element. In a neutral atom, thenumber of positively charged protons and negatively charged electrons is equal. Thenumber of neutrons, however, can vary, forming different isotopes of the atom.

The atoms of most elements, except the noble gases found in Column 18 of the peri-odic table, are chemically unstable because their outer electron orbital is not full. As aresult, most atoms tend to bond with other atoms to form compounds. Bonding causeseach atom involved to have a filled outer orbital, making each atom more stable inthe bonded state.

Chemical bonds are typically categorized as covalent or ionic. In this unit, only cova-lent bonds are modeled. In general, a covalent bond is formed when two atoms sharethe same electrons. Groups of atoms held together by covalent bonds tend to formmolecules. The resulting compounds are called molecular compounds. An example ofthis is water. Covalent bonds can be single, double, or triple, referring to the numberof electrons that are shared between the atoms. In single bonds, two electrons (onefrom each atom) are shared. Double bonds have four shared electrons. Triple bondshave six shared electrons.

In ionic compounds, electrons are transferred from one atom to another. The resultingpositively and negatively charged particles, called ions, are held together by theattraction between their opposite charges. However, they do not form distinct mole-cules. For example, a crystal of table salt has positive sodium ions and negative chlo-ride ions in a 1:1 ratio. Atoms held together by ionic bonds tend to form matrices, andthe resulting compounds are generally referred to as nonmolecular compounds. Acommon example is NaCl, table salt.

Ionic bonds are formed when one atom “borrows” one or more electrons from anotheratom, forming two ions, each having an electrical charge opposite to the other. Theseopposing charges cause the ions to be attracted to each other.

“Sharing” and “borrowing” of electrons between atoms can be more accuratelydescribed using the concept of electronegativity. Electronegativity is a measure of theattraction between an atom’s nucleus and bonded electrons. This property deter-mines the type of bond formed between atoms. If the difference in electronegativitybetween two atoms is great, the bond they form is ionic, which means that the elec-trons involved in the bond spend more of their time orbiting the more electronegativeatom. If the difference in electronegativity is not so great, the bond is considered cova-lent, because the electrons spend approximately equal amounts of time orbiting eachatom.

In this activity, the atomic models are presented as spheres with spikes representingtheir bonding sites. At a more sophisticated level, students would view the models asthe spherical center representing the nucleus and the spikes as unpaired electrons.They would see covalent bonding as the sharing of previously unpaired electrons witheach bonding tube representing a pair of electrons.


B-60


GETTING STARTED

1. Introduce the molecular model set as a toolfor studying atoms and molecules.

Ask students to recall that an atom is the smallestbuilding block of matter, and an element is com-posed of only one type of atom. Familiarize studentswith the molecular model that they will first use inthis activity. Distribute a molecular model set toeach pair of students. A complete set should contain4 elements (black, white, blue, and red) and 64atoms (32 white, 18 black, 14 red, 4 blue). The setalso contains 54 white “bonds.” Once they beginthe activity, students will see in their Student Booksthat white represents hydrogen, black representscarbon, red represents oxygen, and blue representsnitrogen. Impress on students that the colors do notcorrespond to actual physical properties of theatoms, and so should not be viewed as important.In this unit they are only used to distinguishbetween atoms having different numbers of bond-ing sites.

Tell students that the spherical center of each modelrepresents the center of the atom, while the pro-truding “sticks” represent the bonding sites. If yourstudents are familiar with nuclei and electrons, youcan explain that the center of the model representsthe nucleus and the protruding sticks representelectrons that can be shared with another atom toproduce a bond. The white tubes, which connect, orbond, atoms together, fit over the “sticks” of theatoms.

n Teacher’s Note: The holes in the atoms are arti-facts of the manufacturing process and are not to beused when making molecules.

Be sure to point out that the models represent someaspects of the structure and behavior of atoms, butthat they are not at all to scale in their representa-tion of the size of the center and bonding sites of anatom or in showing the differences between atomsof different elements, other than the usual numberof bonding sites. Also stress that a bond is not anobject, but a force of attraction that holds atomstogether to form a molecule.

DOING THE ACTIVITY

2. Introduce Strategies for Reading ScientificProcedures

Reading scientific procedures is a genre of readingunique from other types of reading in that its goal isto complete a series of steps in a specific order tocomplete a task. The most frequent obstacle thatarises when student read a scientific procedure isthat they do no understand what the procedurestep is asking him or her to do. This impedes theirability to complete the investigation. To strengthentheir ability to read and understand procedures,introduce the strategies shown on Literacy Trans-parency 3, “Reading Scientific Procedures.” Modelhow these reading strategies, if used frequently, willincrease students’ ability to read and work inde-pendently.

In introducing these strategies is it important thatyou model how they can be used. Act them out. Finda complicated scientific procedure that you are notfamiliar with and show students how you might getstuck, and then model how you might use thestrategies to independently determine what to donext. Show them how you would use the strategiesto figure out what to do. Provide many opportuni-ties for students to practice the strategies. Reinforcethe use of the strategies when students are workingwith procedures that are challenging. Most impor-tantly, continue to reinforce student use of thestrategies to foster independent reading skills.

3. Students build models of molecules.

For Procedure Step 3 review with students the nota-tion for writing chemical formulas. Students willneed to understand that elements are written usingthe capitalized chemical symbols shown on theperiodic table. The number of atoms in one mole-cule is noted by writing the number as subscriptafter the atomic symbol. Point out that when thereis one atom in a molecule, such as the one oxygenmolecule in H2O, the one is not written, it is implied.

This activity is exploratory in nature and will helpstudents realize that each type of atom can bejoined to others only in certain ways. In some cases,atoms of the same element can form single or multi-ple bonds with each other. It is all right if students


B-61

come up with combinations that do not take placein nature. Here it is important for them to see thebonding possibilities and to discover that doubleand triple bonds can form. At this point, allow stu-dents to build all possible molecules when combin-ing different atoms according to the rules provided.Students may come up with actual compounds,such as HNO3 (nitric acid) and H2O2 (hydrogenperoxide).

You may wish to stop after students have completedProcedure Part A , “Making Simple Molecules,” anddiscuss what they have discovered so far. Encouragegreater independence as they move on to Part B,“Making More Complex Molecules.”

Sample student diagrams and answers to the proce-dure steps follow.

Procedure Steps 2 and 3

Procedure Step 5

Procedure Step 6

Procedure Step 7

Procedure Step 15

FOLLOW-UP

4. (UC ASSESSMENT) The class discusses theprinciples illustrated by the model-buildingexperience.

Ask students, What information do the models showabout atoms, elements, and molecules? The modelset includes models of the atoms for four elements.Students should comment that each model atomshows the number of bonds that a particular atomcan make. From this information students can pre-dict the molecules the atom can form and the for-mulas of compounds that will result. Ask them tochoose one of the atoms and describe what themodel shows about its chemical properties and itsbonding to hydrogen. For example, nitrogen tendsto make three bonds and hydrogen tends to makeone bond. Thus one nitrogen atom will combinewith three hydrogen atoms, and the formula of theresulting compound is NH3. Relate these to the for-mulas given on the Element Cards students used inActivity 15, “Families of Elements.”

Point out that some elements, such as oxygen andnitrogen, can also form molecules. The oxygen andnitrogen in air are elements, but they are present asmolecules with two atoms. Even though they areelements, their formulas as they exist in nature areO2 and N2. Hydrogen also exists as a molecule (H2).

Project the transparency of Student Sheet 16.1,“Periodic Table of the Elements,” and ask studentsto consult their copies of the periodic table either onStudent Sheet 16.1, or in the Student Book. Note theplacement of the elements that the students havebeen working with. Remind them that each columncontains elements that have similar chemical prop-erties. Point out that these chemical properties arerelated to the ability of an atom to form bonds withother atoms. Ask, Given that nitrogen forms threebonds with hydrogen to make NH3, how many hydro-gen atoms do you think will bond with an atom ofphosphorus? Students should be able to predict thatphosphorus would bond with three hydrogenatoms to form PH3. Based on observations theymade when using the molecular model sets, andbecause phosphorus is in column 15 underneaththe element nitrogen, a phosphorus atom, like

Water, H2O

H

O

H

HH

Methane, CH4

C

H

Ammonia, NH3

N

HH H H

Oxygen, O2

O O

Carbon Dioxide, CO2

OCO


B-62

nitrogen, would bond with three hydrogen atoms.Similarly, and using the same thinking, studentsshould also predict that sulfur, like oxygen, wouldbond with two hydrogen atoms; and sodium, likehydrogen, with one. Use this line of questioning toreinforce that the Periodic Table is a tool that can beused to predict and describe the properties of ele-ments and the bonds that form between elements.

Analysis Question 6 presents an opportunity for stu-dents to show their understanding of the relation-ship between an atom and a molecule by making adrawing. Encourage them to include labels and anexplanatory written description of what theiranswer shows about the relationship. Let studentsknow that you will be scoring this with the UNDER-STANDING CONCEPTS (UC) Scoring Guide. Review withstudents your expectations for this assessment item.You might have partners review each other’s dia-grams for clarity and accuracy, and allow them toimprove their diagrams based on that feedbackbefore you collect and score them.

Analysis Question 7 asks students to think about thestrengths of a molecular drawing versus a struc-tural formula. To stress the point that eachdescribes stresses different information, ask severalstudents to share their sketches with the class. Pointout variations among students’ sketches. Explainthat scientists have agreed on a standardizedmethod of representing molecules called a “struc-tural formula.” Using a standardized approachhelps scientists avoid miscommunication.


1. How many different elements were you

working with?

We were working with four different elements(carbon, hydrogen, oxygen, and nitrogen).

2. What was the role of the “sticks” on each

atom model?

Each stick represented a site that could make achemical bond.

3. Was it possible for an atom to make more than one

bond? Explain, and give an example.

All of the atoms except hydrogen could makemore than one bond. For example, oxygen couldmake two bonds because it had two projections.(Nitrogen could make 3 bonds, and carboncould make 4.)

4. How many bonds could each of the following to

make with hydrogen? Copy the table below into your

science notebook. Use the atomic numbers to help

you find the elements on the periodic table.

a. Si (Atomic # 14) 4

b. Se (Atomic # 34) 2

c. I (Atomic #53) 1

d. As (Atomic # 33) 3

5. If you had two oxygen atoms and one hydrogen

atom, could you form a molecule? Explain.

No. If you had two oxygen atoms and one hydro-gen atom, you could join the two oxygens andhave a hydrogen at the end, but one of the oxy-gens would have an unbonded site. There is noway to put them together so that all bondingsites are bonded.

6. (UC ASSESSMENT) Make a drawing of the models

to show the difference between an atom and a mole-

cule.

A complete and correct answer will show anatom as a part of a molecule as shown in the fig-ure below.

Level 3 Response

A molecule is made of more than one atom. Itcan be more than one of the same atom, like amolecule of oxygen contains two oxygen atoms.Or, it can be composed of more than one. Like amolecule of water is made up of two differenttypes of atoms, hydrogen and oxygen.

AtomH

O

H

Molecule


B-63

7. Which model provides more information—a chemi-

cal formula or a sketch of the molecule?

It depends on the information you need about acompound. In general, a sketch provides moreinformation about what a molecule looks like,because the bonds between each atom areshown clearly. A chemical formula is useful ifyou need to know what type of atoms and theiramounts are contained in a molecule.

TEACHER RESOURCES • ASSESSMENT III

123



Student accomplishes Level 3 AND goes beyond in some significant way, such as: • using relevant information not provided in

class to elaborate on your responsee. • using a diagram to clarify scientific concepts. • relating the response to other scientific

concepts.


Student accurately and completely explains or uses relevant scientific concepts.

Level 2Almost there

Student explains or uses scientific concepts BUT has some omissions or errors.

Level 1On your way

Student incorrectly explains or uses scientific concepts.

Level 0 Student’s response is missing, illegible, or irrelevant.


4. UNDERSTANDING CONCEPTS (UC)

What to look for: • Student’s response identifies and describes scientific concepts relevant to a particular

problem or issue.

©20

15 T

he R

egen

ts o

f the

Uni

vers

ity o

f Cal

iforn

ia

ISSUES AND PHYSICAL SCIENCE LITERACY TRANSPARENCY 3

Issues and Physical Science, 2nd Edition - Lab Aids Act 15-17... · Section Preview of the...

Documents

Transcript of Issues and Physical Science, 2nd Edition - Lab Aids Act 15-17... · Section Preview of the...