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Glencoe Science

Chapter Resources

Chemical Reactions

Includes:

Reproducible Student Pages

ASSESSMENT

✔ Chapter Tests

✔ Chapter Review

HANDS-ON ACTIVITIES

✔ Lab Worksheets for each Student Edition Activity

✔ Laboratory Activities

✔ Foldables–Reading and Study Skills activity sheet

MEETING INDIVIDUAL NEEDS

✔ Directed Reading for Content Mastery

✔ Directed Reading for Content Mastery in Spanish

✔ Reinforcement

✔ Enrichment

✔ Note-taking Worksheets

TRANSPARENCY ACTIVITIES

✔ Section Focus Transparency Activities

✔ Teaching Transparency Activity

✔ Assessment Transparency Activity

Teacher Support and Planning

✔ Content Outline for Teaching

✔ Spanish Resources

✔ Teacher Guide and Answers

Glencoe Science

Photo CreditsSection Focus Transparency 1: Richard Megna/Fundamental Photographs;Section Focus Transparency 2: Reuters NewMedia Inc./CORBIS

Copyright © by The McGraw-Hill Companies, Inc. All rights reserved.Permission is granted to reproduce the material contained herein on the conditionthat such material be reproduced only for classroom use; be provided to students,teachers, and families without charge; and be used solely in conjunction with theChemical Reactions program. Any other reproduction, for use or sale, is prohib-ited without prior written permission of the publisher.

Send all inquiries to:Glencoe/McGraw-Hill8787 Orion Place Columbus, OH 43240-4027

ISBN 0-07-867152-3

Printed in the United States of America.

1 2 3 4 5 6 7 8 9 10 079 09 08 07 06 05 04

Chemical Reactions 1

ReproducibleStudent Pages

Reproducible Student Pages■ Hands-On Activities

MiniLAB: Observing the Law of Conservation of Mass. . . . . . . . . . . . . 3MiniLAB: Try at Home Identifying Inhibitors . . . . . . . . . . . . . . . . . . . 4Lab: Physical or Chemical Change? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Lab: Design Your Own Exothermic or Endothermic? . . . . . . . . . . . . . . 7Laboratory Activity 1: Chemical Reactions. . . . . . . . . . . . . . . . . . . . . . 9Laboratory Activity 2: Reaction Rates and Temperature . . . . . . . . . . 13Foldables: Reading and Study Skills. . . . . . . . . . . . . . . . . . . . . . . . . . 17

■ Meeting Individual NeedsExtension and Intervention

Directed Reading for Content Mastery . . . . . . . . . . . . . . . . . . . . . . . 19Directed Reading for Content Mastery in Spanish . . . . . . . . . . . . . . 23Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Enrichment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Note-taking Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

■ AssessmentChapter Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Chapter Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

■ Transparency ActivitiesSection Focus Transparency Activities . . . . . . . . . . . . . . . . . . . . . . . . 42Teaching Transparency Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Assessment Transparency Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

2 Chemical Reactions

Hands-OnActivities

Hands-On Activities

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Observing the Law ofConservation of Mass

Procedure1. Place a piece of steel wool into a medium test tube. Seal the end of the test

tube with a balloon.

2. Find the mass.

3. Using a test tube holder, heat the bottom of the tube for two minutes in a hot water bath provided by your teacher. Allow the tube to cool completely.

4. Find the mass again.

Analysis1. What did you observe that showed a chemical reaction took place?

2. Compare the mass before and after the reaction.

3. Why was it important for the test tube to be sealed?

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Identifying InhibitorsProcedure1. Look at the ingredients listed on packages of cereals and crackers in

your kitchen.

2. Note the preservatives listed. These are chemical inhibitors.

3. Compare the date on the box with the approximate date the box was purchased to estimate shelf life.

Analysis1. What is the average shelf life of these products?

2. Why is increased shelf life of such products important?

Hands-On Activities

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Lab PreviewDirections: Answer these questions before you begin the Lab.

1. How can you tell if a chemical change has taken place?

2. What material in this activity can cause skin and eye irritation?

Matter can undergo two kinds of changes—physical and chemical. Aphysical change affects the physical properties. When a chemical changetakes place, a new product is produced.

Physical or Chemical Change?

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Real-World QuestionHow can a scientist tell if a chemical changetook place?

Goals■ Determine if a physical or chemical change

took place.

Safety Precautions

WARNING: Vinegar (acetic acid) may causeskin and eye irritation.

Materials500-mL Erlenmeyer flask1000-mL graduated cylinderone-hole stopper with 15-cm length of glass

tube inserted1000-mL beaker45-cm length of rubber (or plastic) tubingbalancestopwatch or clock with second handweighing dishbaking sodavinegar

Procedure1. Measure 300 mL of water. Pour water into

500-mL Erlenmeyer flask.2. Weigh 15 g of baking soda. Carefully pour

the baking soda into the flask. Swirl theflask until the solution is clear.

3. Insert the rubber stopper with the glasstubing into the flask.

4. Measure 600 mL of water and pour intothe 1000-mL beaker

5. Attach one end of the rubber tubing to thetop of the glass tubing. Place the other endof the rubber tubing in the beaker. Be surethe rubber tubing remains under the water.

6. Remove the stopper from the flask. Care-fully add 250 mL of vinegar to the flask.Replace the stopper.

7. Count the number of bubbles coming intothe beaker for 20 s. Repeat this two moretimes.

8. Record your data on the Data Table.


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Data Table

Hands-On Activities

Communicating Your Data

Compare your results with those of other students in your class.

Conclude and Apply1. Describe what you observed in the flask after the acid was added to the baking soda solution.

2. Classify Was this a physical or chemical change? How do you know?

3. Analyze Results Was this process endothermic or exothermic?

4. Calculate the average reaction rate based on the number of bubbles per second.

Number of Bubbles

First Test

Second Test

Third Test

(continued)

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Lab PreviewDirections: Answer these questions before you begin the Lab.

1. Why should you wash your hands after completeing the lab?

2. What happens to energy in an exothermic reaction?

Energy is always a part of a chemical reaction. Some reactions need energyto start. Other reactions release energy into the environment. Think aboutthe difference between these two types of reactions.

Design Your Own

Exothermic or Endothermic?

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Real-World QuestionWhat evidence can you find to show that a reac-tion between hydrogen peroxide and liver orpotato is exothermic or endothermic?

Form a HypothesisMake a hypothesis that describes how you canuse the reactions between hydrogen peroxideand liver or potato to determine wether a reac-tion is exothermic or endothermic.

Goals■ Design an experiment to test whether a

reaction is exothermic or endothermic.■ Measure the temperature change caused by

a chemical reaction.

Possible Materialstest tubes (8) raw potatotest-tube rack thermometer3% hydrogen stopwatchperoxide solution clock with second hand

raw liver 25-mL graduated cylinder

Safety Precautions

WARNING: Hydrogen peroxide can irritateskin and eyes and damage clothing.Be careful when handling glass thermometers.Test tubes containing hydrogen peroxide should be placed and kept in racks. Dispose of

materials as directed by your teacher.Wash your hands when you complete this lab.

Test Your HypothesisMake a Plan1. As a group, look at the list of materials.

Decide which procedure you will use totest your hypothesis, and which measure-ments you will make.

2. Decide how you will detect the heat releasedto the environment during the reaction.Determine how many measurements youwill need to make during a reaction.

3. You will get more accurate data if yourepeat each experiment several times. Eachrepeated experiment is called a trial. Use theaverage of all the trials as your data for sup-porting your hypothesis.

4. Decide what the variables are and whatyour control will be.

Follow Your Plan1. Make sure your teacher approves your plan

before you start.2. Carry out your plan.3. Record your measurements immediately

in the table in the Data and Observationssection.

4. Calculate the averages of your trial resultsand record them.


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Data and Observations

Hands-On Activities

Communicating Your DataCompare the results obtained by your group with those obtained by other groups. Arethere differences? Explain how these might have occurred.

Analyze Your Data1. Can you infer that a chemical reaction took place? What evidence did you observe to support this?

2. Identify what the variables were in this experiment.

3 Identify the control.

Conclude and Apply1. Do your observations allow you to distinguish between an exothermic reaction and an

endothermic reaction? Use your data to explain your answer.

2. Where do you think that the energy involved in this experiment came from? Explain your answer.

Total

Temperature afterAdding Potato (˚C)

Starting

1

2

3

4

Temperature afterAdding Liver (˚C)Trial

Average

After min Starting After min

(continued)

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Chemical Reactions

The changes that occur during a chemical reaction are represented by a chemical equation. Anequation uses chemical symbols to represent the substances that change. The reactants, on the leftside of the equation, are the substances that react. The products, on the right side of the equation,are the substances that are formed from the reaction.

In the following reaction, two reactants form one product. Water and oxygen are the reactants.The product is hydrogen peroxide.

H2O + 1–2O2 → H2O2

A chemical reaction may have two products from the breakdown of a single reactant. In thisexample water is the reactant. Hydrogen and oxygen are products.

2H2O → 2H2 + O2

Two reactants can also combine to make two products. In the following reaction, carbon dis-places the hydrogen in water and hydrogen and carbon monoxide are released as gases.

H2O + C → H2 + CO

StrategyYou will recognize the reactants and products of a chemical reaction.You will write a word equation for a chemical reaction.You will write a balanced chemical equation using chemical symbols.

Materials

LaboratoryActivity11

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Part Aaluminum foilburnermatchestongssteel wool

Part Bmatchestest tubespoonbaking soda, NaHCO3

test-tube holderwood splint

Part Ccommon nail, Festeel woolstringbeakercopper (II) sulfate solution,

CuSO4

watch or clockpaper towel

WARNING: Copper (II) sulfate solution is poisonous. Handle with care. Wear goggles and an apron.

ProcedurePart A—Two Reactants→One Product1. Observe the color of the steel wool. Record

your observations in the Data and Obser-vations section.

2. Predict changes in the steel wool when it isheated in the flame. Write your predictionin the Data and Observations section.

3. Protect the table with a sheet of aluminumfoil. Place the burner in the center of thefoil. Light the burner. WARNING: Stayclear of flames.

Steel wool

Figure 1


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Laboratory Activity 1 (continued)

Name Date Class

4. Hold the steel wool (containing iron, Fe)with the tongs over the flame as shown inFigure 1. As the steel wool burns, recordthe changes it goes through.

Part B—One Reactant→Two Products1. Use the burner set up in Part A.2. Place a spoonful of baking soda, NaHCO3,

in a test tube. Use the test-tube holder toheat the test tube in the flame, as shown in Figure 2. Do not point the mouth of the testtube toward anyone. In the Data and Obser-vations section, write your prediction ofwhat will happen as the baking soda isheated.

3. Record the description and colors of theproducts formed inside the tube as it isheated.

4. Test for the presence of CO2. Light awooden splint. Insert the flaming splintinto the mouth of the test tube. If theflame of the splint goes out, CO2 is present.Record your observations of the productsof this reaction.

Part C—Two Reactants→Two Products1. Carefully rub the nail with a piece of steel

wool until the nail is shiny. Tie a stringaround the nail. Fill a beaker about halffull with the CuSO4 solution. Record thecolors of the nail and the CuSO4 solution inTable 1.WARNING: Use care when handling sharpobjects. Wash hands immediately after coming in contact with copper(II) sulfatesolution.

2. Dip the nail in the CuSO4 solution. (SeeFigure 3.) Predict what changes will hap-pen to the appearance of the nail and thesolution. After 5 min, pull the nail from thesolution and place it on a paper towel.Record the colors of the nail and the solu-tion in Table 1.

3. Put the nail back into the solution andobserve further color changes.

Hands-On Activities

Splint

Baking soda

Figure 2 Figure 3

Data and Observations

Part A—Two Reactants→One Product1. Color of steel wool before burning:

2. Prediction of changes in the heated steel wool:

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3. Color of burned steel wool:

Part B—One Reactant→Two Products4. Prediction of changes in the heated baking soda:

5. Description of deposits inside heated test tube:

6. Observations of flaming splint:

Part C—Two Reactants→Two Products7. Prediction of changes in nail and CuSO4 solution:

Table 1

Questions and Conclusions1. Identify the two reactants in the heating of steel wool.

2. How does the heat from the flame affect the reactants when steel wool is heated?

3. What evidence suggests that at least two reactants were formed when NaHCO3 was heated?

4. Was the heating of NaHCO3 an endothermic or exothermic reaction? Explain your answer.

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8.

Observation time Color of nail

Before reaction

Color of CuSO4 solution

After reaction 10.

9.

11.


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5. From your observations, does the reaction of an iron nail with the copper(II) sulfate yieldmore than one product?

6. Was the addition of the iron nail to the copper(II) sulfate solution an endothermic or exothermic reaction?

Strategy Check

Can you identify the reactants and products of a chemical reaction?

Can you write a word equation for a chemical reaction?

Can you write a balanced chemical equation using chemical symbols?

Hands-On Activities

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Reaction Rates and Temperature

Not all chemical reactions occur at the same rate. Some chemical reactions are very fast; others arevery slow. The same chemical reaction can happen at several different rates depending on the temper-ature at which the reaction occurs

In this experiment, you will investigate the effect of temperature on a decomposition reaction.Household bleach is a solution of five percent sodium hypochlorite (NaClO). This compounddecomposes to produce sodium chloride and oxygen gas.

2NaClO→2NaCl +O2

Materials beaker (400-mL)thermometerpipette, plastic microtip2.5 percent NaClO solutionmicroplate (24-well)

Co(NO3)2 solutionpipette, plasticwashers, iron or lead (3 or 4)clock with second handimmersion heater or hot plate

LaboratoryActivity22

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WARNING: Handle both solutions with care. Solutions can harm clothes and skin.Rinse spills with plenty of water.

ProcedurePart A—Reaction at Room Temperature

1. Safety goggles and a laboratory apron must be worn throughout this experiment.Look at the equation of the decompositionreaction. In the Data and Observationssection, write a prediction of what youmight observe during this reaction. Write a hypothesis describing how temperaturewill affect this reaction rate.

2. Allow 400 mL of tap water to come toroom temperature.

3. At the top of Table 1, measure and recordthe temperature of the water to the nearest0.5°C.

4. Using the microtip pipette, place 30 dropsof 2.5 percent sodium hypochlorite solution in well A1 of the microplate.

5. Rinse the microtip pipette twice with dis-tilled water. Discard the rinse water.

6. Using the rinsed pipette, place 10 drops of cobalt nitrate solution into well C1 ofthe microplate.

7. Rinse the microtip pipette twice with dis-tilled water. Discard the rinse water.

8. Draw up the sodium hypochlorite solu-tion in well A1 into the bulb of the plasticpipette. Be sure that no solution remainsin the stem of the pipette.

9. Place three or four iron or lead washersover the top of the stem of the pipette, asin Figure 1.

10. Turn the pipette upside down and squeezeand hold the pipette to expel the air fromthe bulb of the pipette.

11. While squeezing the pipette, bend the stemof the pipette over into the cobalt nitratesolution in well C1, as shown in Figure 2.Be prepared to start timing the reaction assoon as you complete the next two steps.

12. Release the pipette bulb and draw thecobalt nitrate solution into the pipette.The two solutions will mix. Record anychanges you observe.

StrategyYou will observe the amount of oxygen produced from the decomposition of household bleach

at various temperatures.You will graph the reaction data.You will determine the relationship between reaction rate and temperature for this reaction.


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13. While holding the pipette in place, quicklysubmerge the pipette bulb and washerassembly into the beaker of water asshown in Figure 3. Begin timing. If neces-sary, hold the pipette upright.

14. Count the number of bubbles producedby the reaction as they escape from thestem of the pipette every 15 s for 3 min.rRcord in Table 1 the total number ofbubbles counted for each 15s interval.

15. Use Figure 4 to graph the data from PartA. Plot time on the X axis and the totalnumber of bubbles on the Y-axis. Draw aline that best fits the data points.

Part B—Reaction at a Higher Temperature1. Place the beaker of water in the immersion

bath or on the hot plate. Heat the wateruntil its Celsius temperature is 10° higherthan that of the room temperature water.

2. Repeat steps 3–14 in Part A, using thewater bath at this higher temperature.

3. Plot your data from Part B on the samegraph as Part A, but use a different coloredpen or pencil.

Part C—Reaction at a Lower Temperature1. Fill the beaker with tap water. Add ice to lower

the Celsius temperature of the water 10° belowthat of the room temperature water.

2. Repeat steps 3–14 in Part A, using thewater bath at this lower temperature.

3. Plot your data from Part C on the samegraph as Part A, but use a third color.

Hands-On Activities WashersPlastic pipette

Sodiumhypochloritesolution

24-wellplate

Beaker

Figure 1

Figure 3

Figure 2

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Data and Observations1. Prediction of reaction:

2. Hypothesis relating reaction rate and temperature:

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Table 1

Time (s)

A. Total number of bubbles

(room temperature)

____________ ˚C

0

15

30

45

60

75

90

105

120

135

150

165

180

C. Total number of bubbles

(lower temperature)

____________ ˚C

B. Total number of bubbles

(higher temperature)

____________ ˚C


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Questions and Conclusions1. How does raising the temperature affect the shape of the graphs that you plotted in Figure 4?

2. Describe the relationship between reaction rate and temperature for the decomposition ofsodium hypochlorite.

3. Why is it important that there be no sodium hypochlorite solution in the stem of the pipette instep 8 of the procedure?

4. Soft drinks contain carbonic acid (H2CO3). Carbonic acid decomposes to form water and carbondioxide as shown below H2CO3→ H2O + CO2. Two soft drink bottles are opened, and one is placedin a refrigerator while the other is left at room temperature. The carbonic acid in both bottlesdecomposes, but one bottle goes “flat” faster than the other. Which bottle will go flat first? Explain.

Strategy CheckCan you collect data on the amount of oxygen produced by the decomposition of household bleach?

Can you determine from a graph of the data how the reaction rate differs when the temperature is changed?

Hands-On Activities

Tota

l num

ber o

f bub

bles

Figure 4

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Chemical Reactions

Directions: Use this page to label your Foldable at the beginning of the chapter.

How is a chemical reaction different from a physical change?

What substances are needed for a chemical reaction?

Are atoms ever lost in a chemical reaction?

How can a chemical reaction be speeded up?

Name Date Class

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Meeting Individual Needs


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ContentMastery

OverviewChemical Reactions

Directions: Use the following terms to complete the concept map below. Note that one term will be used morethan once.

concentration reactant endothermic heat energy

rate of reaction catalysts temperature

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Directed Reading for

Content Mastery

Chemical reactions

and release and result in a and absorb

can be can be

1. 2.

at a

exothermic

product4.

5.

3.

6.

particle size

7. 8.

that is affected by

start with a

Name Date Class


Section 1 ■ Chemical Formulasand Equations

Directions: Use the clues given below to complete the crossword puzzle.

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Content Mastery

1 2 3

7

12

1413

10

5

4

6

15

16

9

8

11

Across1. A process that produces a chemical

change (two words)6. Substances produced by a chemical

reaction8. Thermal energy9. Substances on the left side of a

chemical equation11. These structures break in reactants15. Equal numbers of each kind of

atom on each side of the arrow16. The first modern chemist

Down1. Shorthand form for describing a

chemical reaction (two words)2. Reactions that require energy3. Reactions that produce energy4. Neutral subatomic particle5. Change in size, shape, or state

(two words)7. The arrow in a chemical equation

reads as this.10. Tells you the number of atoms of

each element12. Is released or absorbed13. Refers to heat14. The law of conservation of ______

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Section 2 ■ Rates of ChemicalReactions

Directions: Write the word true in the space next to each statement that is true. If the statement is false,rewrite the statement to make it true on the lines provided.

1. A change in state is a physical change.

2. Catalysts speed chemical reactions but are not changed by them.

3. Heat, light, or change in odor can indicate a physical change.

4. Activation energy is the minimum for reactions to start.

5. Cold usually speeds up reaction rates.

6. A low concentration of a chemical slows reaction rate.

7. Chemical reactions occur at the same rate no matter what the size of the

reactant particles.

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Key TermsChemical Reactions

Directions: Write the letter of the correct term in Column II next to its description in Column I.

Column I

1. speeds up a reaction

2. slows down a reaction

3. a reaction that releases heat

4. a reaction that absorbs heat

5. a process that produces a chemical change

6. substance formed by a chemical reaction

7. substance that exists before a reaction begins

8. how fast a reaction occurs

9. the minimum amount of energy needed to start any chemical reaction

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Content Mastery

Column II

a. rate of reaction

b. exothermic reaction

c. product

d. reactant

e. activation energy

f. inhibitor

g. endothermic reaction

h.chemical reaction

i. catalyst

Directions: Circle the terms from Column II in the word search puzzle below.

E

C

T

E

T

N

J

E

S

Y

O

A

E

D

R

H

E

R

O

E

C

U

D

A

N

O

N

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Nombre Fecha Clase

Reacciones químicas 23

ContentMastery

SinopsisReacciones químicas

Instrucciones: Usa los siguientes términos para completar el mapa de conceptos. Observa que uno de los térmi-nos se usa más de una vez.

concentración reactivo endotérmica energía calórica

taza de reacción catalizadores temperatura

Lectura dirigida para

Dominio del contenido

Las reacciones químicas

y liberar y resultan en un y absorber

pueden ser pueden ser

1. 2.

a un(a)

exotérmicas

producto4.

5.

3.

6.el tamaño de las

partículas

7. 8.

afectada por

comienzan con un

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Nombre Fecha Clase

24 Reacciones químicas

Sección 1 ■ Fórmulas y ecua-ciones químicas

Instrucciones: Usa las pistas para completar el crucigrama.

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Horizontales

1. Partícula subatómica neutra2. Esto es lo que significa la flecha en

una reacción química8. Proceso que produce un cambio

químico (dos palabras)10. El primer químico moderno11. Se libera o se absorbe12. El cambio de tamaño, forma o

estado es un cambio _______13. Reacciones que producen energía15. Reacciones que absorben energía

Verticales

1. Te dice el número de protones en elátomo de un elemento

3. Igual número de cada tipo deátomo a ambos lados de la flecha deuna ecuación

4. Sustancias en el lado izquierdo de laflecha de una ecuación

5. Estas estructuras activan a losreactivos

6. Se refiere al calor7. Sustancia que es producida en una

reacción química9. Energía térmica

11. Forma corta y clara para describiruna reacción

14. Ley de conservación de la _______

Satisface las necesidades individuales

N E U T R O N

U P R O D U C E

M R Q

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R R E A C C I

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O N Q U I M I C A R

O C A L L A V O

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O V R E N E R G I A C

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Reacciones químicas 25

Sección 2 ■ Velocidad de unareacción química

Instrucciones: Escribe la palabra verdadero en el espacio al lado de cada afirmación si ésta es verdadera. Si laafirmación es falsa, vuelve a escribir en las líneas de abajo la oración de forma que sea verdadera.

1. Un cambio de estado es un cambio físico.

2. Los catalizadores aumentan la velocidad de las reacciones químicas sin

que ellos mismos cambien.

3. El calor, la luz y el olor indican un cambio físico.

4. La energía de activación es la energía mínima necesaria para iniciar una

reacción.

5. Las tasas de reacción se hacen más rápidas con el frío.

6. La baja concentración de una sustancia química hace más lenta la tasa

de reacción.

7. Las reacciones químicas ocurren a la misma tasa sin importar el tamaño

de las partículas de los reactivos.



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Nombre Fecha Clase

26 Reacciones químicas

Términos clavesReacciones químicas

Instrucciones: Escribe la letra del término correcto de la Columna II a la izquierda de su descripción en la Columna I.

Columna I

1. hace más rápida la reacción

2. hace más lenta la reacción

3. reacción que libera calor

4. reacción que absorbe calor

5. proceso que produce un cambio químico

6. sustancia que se forma en una reacción química

7. sustancia que existe antes de que comience una reacción química

8. la rapidez con que se da una reacción

9. la cantidad mínima de energía que se necesita para comenzar una reacción química

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Columna II

a. tasa de reacción

b. reacción exotérmica

c. producto

d. reactivo

e. energía de activación

f. inhibidor

g. reacción endotérmica

h.reacción química

i. catalizador

Instrucciones: Encierra en un círculo los términos de la Columna II en la siguiente sopa de letras

Satisface las necesidades individuales

E

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Directions: Complete the following sentences by writing the correct terms in the blanks.

1. Chemical changes in a substance result in

2. Physical changes in a substance result in

3. A chemical reaction begins with substances called ____________________ and ends with

substances called ____________________.

4. In a word equation, the substances on the left of the arrow are the ____________________,

and the substances on the right side of the arrow are the ____________________. The arrow

should read as ____________________.

Directions: Answer the following questions on the lines provided5. Give two reasons why scientists prefer to use chemical equations instead of word equations.

a.

b.

6. What do the subscripts in a chemical equation tell about the equation?

7. Suppose you have a holiday celebration and over the evening six logs are burned in a fireplace.All that’s left is ashes, but you know that there are just as many atoms as there were before—they’re just in a different form. Explain how you know that.

8. The fire in the fireplace is an example of an exothermic reaction. Explain what happens in anexothermic reaction.

9. In one of the lab experiments you observed, water was split into hydrogen and oxygen in anendothermic reaction. Explain what happens in an endothermic reaction.

10. If the equation below is balanced, write Yes on the line provided. If it is not balanced, write No.

a. 2Na + 2H2O→2NaOH + H2

b. 4Al + 3O2→Al2O

c. NH4OH + HC2H3O2→NH4C2H3O2 + H2O

d. 2A1 + 6NaOH→2Na3AlO3 + 2H2

Chemical Formulasand Equations

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Rates of Chemical Reactions

Directions: Use the clues to complete the puzzle.

Reinforcement22


1

5

6

4

8

2

3

11

9

10

7

Across

2. It speeds up a reaction but is not perma-nently changed

3. It slows down a chemical reaction

7. The minimum amount of energy neededto start any reaction (2 words)

9. By decreasing this, you can speed up achemical reaction (2 words)

10. Increasing this speeds up most chemicalreactions

11. Enzymes that break down proteins

Down

1. Amount of substance present in a certainvolume

4. They are broken before a chemical reaction takes place

5. Measure of how fast a reaction occurs(two words)

6. These must be strong in order to cause achemical change to take place

8. Catalysts at work in the body

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Playing with Copper

Pennies aren’t made of copper alone, but they are part copper. That copper allows you to dosome pretty amazing chemical experiments with a penny. Here are a few you can try.

Part AAfter a new penny has been left outside for a while it loses its shine. The oxygen in the air

causes it to change color. The result is a new compound, copper oxide, which coats the surface ofthe penny.

1. Write an equation to show what happens.

Part BPut a few pinches of salt in a small bowl, add about 60 mL of vinegar, and stir until the salt

dissolves. Hold an old penny halfway into this salt and vinegar solution and count slowly to 30.Pull the penny out of the mixture.

2. Describe the appearance of the penny.

3. In your own words, describe what happened to the copper oxide.

Part CPut a square piece of paper towel on a small plate. Place several pennies on the paper towel and

pour the salt and vinegar mixture over the pennies. Wait several hours and then observe the penny.

4. Describe the results of this experiment.

5. Where else have you seen something that looks like the bluish-green copper compound in malachite?

Enrichment11

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Slow and Fast

Materials plain steel wool candletongs glass or plastic dish

Procedure

Part A. Fast Reaction1. Measure the mass of your piece of steel

wool to the nearest 0.01 g. Record the massin the data table on this page.

2. Predict what you think will happen to themass of the steel wool when it is heated in aflame. Record your prediction and reasonsin the data table. WARNING: Use carearound open flames.

3. Use the tongs to hold the steel wool in thecandle flame for several minutes.Take the steel wool out of the flame and let it cool. Record your observations.

4. Measure the mass of the steel wool andrecord it in the data table.

5. Repeat steps 3 and 4 until you do notdetect any further change in mass.

Part B. Slow Reaction1. Measure the mass of the second piece of

steel wood to the nearest 0.01 g. Record themass in the data table.

2. Wet the steel wool thoroughly with water.Place the steel wool in the dish for severaldays at room temperature.

3. Predict what you think will happen to themass of the steel wool. Record your predic-tion and reasons in the data table.

4. After the steel wool has completely dried,measure and record its final mass.

Enrichment22


Initial mass

Prediction

Reasons

Observations

Final mass

Part A Part B

Questions1. What happened to the mass of the steel wool in part A?

2. What happened to the mass of the steel wool in part B?

3. Explain your results for parts A and B.

4. Why was the reaction more rapid in Part A?

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Chemical Reactions

Section 1 Chemical Formulas and Equations

A. Matter can change physically or chemically; a process that produces a chemical change is achemical __________________.

B. A chemical __________________ is a shorthand form of what reactants are used and whatproducts are formed in a chemical reaction.

1. Some equations use _______________ or chemical ________________to identify reactantsand products.

2. Chemical __________________ represent chemical names of substances in a chemicalequation.

C. The mass of reactants and mass of products in a chemical reaction is always the same due to

the law of ______________________________.

D. Chemical equations are __________________ when the number of atoms is the same on eachside of the equation.

E. ________________ is released or absorbed during a chemical reaction.

1. When reactions release energy (____________________ reactions), the products havebonds with less energy than those of the reactants.

2. When reactions absorb energy (_____________________ reactions), the reactants aremore stable and their bonds have less energy than those of the products.

3. ______________ energy may be absorbed or released; the rate of heat release can be rapidor slow.

4. The word energy can be written in a ___________________equation as a reactant or aproduct.

Section 2 Rates of Chemical Reactions

A. Different chemical reactions take different amounts of ______________.

B. ____________________ energy—the amount of energy needed to start a chemical reaction

C. The rate of __________________ measures how quickly a reactant is disappearing or howquickly a product is appearing.

1. Tells how quickly the amount of a ___________________ changes per unit of time

2. Importance in industry: the faster a product can be made, the lower its _______.

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3. _____________________ can change the rate of reaction.

4. _______________________, the amount of a substance present in a specific volume, affectsthe rate of reaction.

5. _______________________ affects the speed of a reaction.

D. ___________________—a substance that slows down the rate of a chemical reaction

E. __________________—a substance that speeds up a chemical reaction; enzymes are specialprotein molecules that act as catalysts in the body.


Note-taking Worksheet (continued)


Assessment

Assessment

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Chapter Review

Name Date Class

Chemical Reactions

Part A. Vocabulary ReviewDirections: Match the items in Column II with the definitions in Column I. Write the letter of the correct term inthe blank at the left.

Column II

a. activation energy

b. catalyst

c. chemical reaction

d. endothermic reaction

e. exothermic reaction

f. inhibitor

g. product

h. rate of reaction

i. reactant

Column I

1. process that produces chemical change

2. substance that slows down a chemical reaction

3. reaction in which heat energy is absorbed

4. substance that exists before a chemical reaction begins

5. minimum amount of energy needed in order for a reaction to begin

6. substance formed by a chemical reaction

7. substance that speeds up a chemical reaction

8. reaction in which heat energy is released

9. a measure of how fast a reaction occurs

Part B. Concept ReviewDirections: In the space before each equation, write a B if the equation is balanced or a U if the equation is unbalanced.

1. MgCO3 + 2HCl→MgCl2 + H2CO3

2. 2H2 + O2→H2O

3. CaCl2→2Ca +Cl2

4. Zn + 2HCl→ZnCl2 + H2

Directions: In the space at the left, write the letter of the answer that best completes the statement or answersthe question.

5. Evidence that a chemical change has occurred includes a ______.a. change in state c. change in shapeb. change in size d. change in color

6. An oven’s high temperature speeds up chemical reactions because heat ______.a. lowers the activation energyb. activates catalystsc. makes more molecules collide with each otherd. reduces the particle size of the reactants

Asse

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Chapter Review (continued)


7. You can slow down the rate of a reaction by ______.a. increasing concentration c. decreasing particle sizeb. increasing temperature d. adding an inhibitor

8. Which of the following is not an example of an exothermic reaction?a. the splitting of water into hydrogen and oxygenb. fireworks explodingc. fish that emit lightd. propane and oxygen changing into carbon dioxide and water

9. In an exothermic reaction, heat is ______.a. absorbed c. releasedb. conserved d. destroyed

10. Activation energy is necessary for a chemical reaction to occur because ______.a. breaking bonds requires energyb. some reactions happen at cold temperaturesc. all reactions are endothermicd. forming bonds requires energy

11. A chemical that keeps food from spoiling is an example of ______.a. a catalyst c. a reactantb. an enzyme d. an inhibitor

12. Presence of a catalyst ______.a. stops a reaction c. slows down a reactionb. raises the activation energy needed d. reduces the activation energy needed

13. To check whether an equation is balanced, ______.a. add the number of reactants to the number of productsb. make sure the masses of the reactants and products are the samec. count the number of each type of atom on each sided. check to see if the reaction is endothermic or exothermic

14. Energy is usually only shown with the products in an equation for ______.a. an endothermic reaction c. an exothermic reactionb. a synthesis reaction d. activation energy

15. The only balanced equation shown is ______.a. H2 + O2 →H2 O c. Ag + H2S→Ag2S + H2

b. AgNO3 + NaI→AgI + NaNO3 d. Na + Cl2→NaClAssessm

ent

Transparency Activities


Tran

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Section FocusTransparency Activity11


This copper penny is immersed in nitric acid. Nitric acid is made of nitrogen, oxygen, and hydrogen. Most of the bubbles consist ofnitrogen and oxygen.

I Needed That Penny.

1. Describe what is happening in the picture. Would the same reaction occur if you put the penny in water?

2. What clues do you have that a chemical change is taking place?

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Section FocusTransparency Activity22

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In 1997, a local man in Siberia discovered part of a mammoth sticking out of the ice. In fact, some of it was encased in ground thatnever thaws. Portions of the mammoth’s skin, hair, and organs werepreserved, enabling scientists to study soft parts of the creature thatordinarily disappear quickly after death.

Preserved Mammoth

1. Compare food stored in the freezer to food that is left on thecounter.

2. What advantages does the ice-bound mammoth offer to scientists?

3. Do you think such finds are common? Why or why not?

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Teaching TransparencyActivity11 Reactions Around

the Home

Tabl

e 1

Rea

ctio

ns A

roun

d th

e H

ome

Reac

tant

sPr

oduc

ts

Baki

ng so

da �

Vine

gar

→Ga

s�W

hite

solid

Char

coal

� A

ir→

Ash

� G

as �

Hea

t

Iron

� A

ir→

Rust

Silv

er�

Air

→Bl

ack

tarn

ish

Gas (

kitc

hen

rang

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Air

→Ga

s� H

eat

Tea

� L

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juic

e→

Ligh

ter-

colo

red

tea


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Teaching Transparency Activity (continued)

1. How is a chemical change different from a physical change?

2. Which reactants yield rust as a product?

3. Which reactions have heat among the products?

4. What gas is produced when baking soda and vinegar combine?

5. Use words to describe the reaction between baking soda and vinegar. On the next line, writethe same reaction using chemical formulas.


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AssessmentTransparency Activity

Tran

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Act

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Directions: Carefully review the table and answer the following questions.

Chemical Reactions

1. According to the table, which is the only equation that does notcontain the molecular form of oxygen (O2)?A 1B 2C 3D 4

2. This table shows the equations as being exothermic or endothermic.Based on the information given, a reasonable description ofexothermic reactions would be ___.F reactions that make new compoundsG reactions that need energy to startH reactions that release heatJ reactions that decompose into smaller parts

3. Calcium carbonate has one atom of calcium, one atom of carbon,and three atoms of oxygen. According to the table, which formularepresents calcium carbonate?A CaOB CO2

C CaCO3

D CO

Reactants

1. 4K�O2

2. 2CO�O2

3. 2H2O�heat

4. CaCO3�heat

Products Type of reaction

2K2O�heat

2CO2�heat

2H2�O2

CaO�CO2

Exothermic

Exothermic

Endothermic

Endothermic

chemical reactions - pc\|macimages.pcmac.org/sisfiles/schools/al/limestone... · 2 chemical...

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