True Solutions NOTES Chemistry Vista Overview

Chemistry Vista

True Solutions

Overview

Students investigate density, buoyancy, and viscosity.

General Time Frame

5-8 lessons (55 minutes each)

Background Information for the Vista

As noted in the chart below, students have prior knowledge of density from grades 4 through 8.

Grade 4

4.7(B)

Grade 5

5.7(A)

Grade 6

6.7(B)

Grade 7

7.7(A)

Grade 8

8.9(A)

The concept of density is introduced in Grade 4. By Grade 8, it is usually defined as mass divided by volume. Middle school students are often asked to calculate density, but are unable to conceptualize the uniqueness and significance of this intrinsic property.

So what is density? The concept of density can be understood by developing a definition based on observations—an operational definition.

An operational definition of density, one applicable to any substance, states that density is the quantity of matter contained in one cubic centimeter of space. Density is often used to describe the nature of a substance. The density of a uniform piece of matter is constant. At the molecular level, density is determined by the amount of space between molecules as well as the mass of the molecules. The more empty spaces between the molecules, the less dense the matter. The marbles used in two of the learning experiences in this vista represent the particles within matter, and help students understand that density is the factor of BOTH mass and volume.

NOTES

Test your students’ understanding of density with the old puzzle, “Which is heavier: a pound of gold or a pound of feathers?” Initially, before giving much thought to the actual question, most students will say gold. What the paradox is really referring to is density. If a visual is added, showing the

The Charles A. Dana Center at UT Austin 1

NOTES drastic difference between the volumes of the two samples, some students may be swayed to say feathers. In this vista, Learning Experience 1 challenges students to break through their misconceptions about density and develop an operational definition.

Buoyancy is also introduced in Grade 4 and is often defined as the ability of an object to float. Quantitatively, buoyancy is the upward force exerted on a body in a fluid. This buoyant force (F b weight (F g

= 9.8 m/s 2

) on a submerged object is equal to the

• mass of object) of the fluid displayed by the object.

The weight of the displaced fluid depends on the volume of the object. The principle operating in this situation is known as the Archimedes’ Principle (see

Figure 1) .

Figure 1: Archimedes’ Principle

An object floats when the weight of the displaced fluid is equal to the weight of the object. An object will sink when the weight of the displaced fluid is less than the weight of the object. Thus, if the object’s density is less than the fluid’s density, the object will float. This principle is useful for determining the volume and, therefore, the density of an irregularly shaped object. Archimedes found that the density of the king’s supposedly gold crown was actually much less than the density of gold.

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In the above picture, cubes of cork, aluminum and lead with densities of

.2g/cm 3 , 2.7g/cm 3 , and 11.3g/cm 3 were placed into a container of distilled water. Each cube has a volume of 10 cm 3 , causing each to displace 10 g of water (density of distilled water is 1g/ml). Therefore, the buoyant force (F b acting on each object is the same. Using the data, the mass of each sample

)

Integrated Physics and Chemistry Institute – Fall 2004 The Charles A. Dana Center at UT Austin

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NOTES can be calculated: mass of cork 2g; mass of aluminum 27 g; mass of lead 113g.

Differences in the way each sample behaves in water can be explained by the differences in their masses. Different masses mean different weights (F g

). The cork floats, the aluminum sinks, and the lead sinks faster than the aluminum.

Viscosity is an internal property of a fluid that offers resistance to flow.

High viscous fluids resist flow; low viscous fluids flow easily. The tenacity with which a moving layer of fluid drags adjacent layers of fluid along with it determines its viscosity. A fluid’s viscosity is usually measured with a viscometer, a container with a standard-sized hole in the bottom. The rate at which the fluid flows through the orifice is its viscosity. In Learning

Experience 3, we will measure the flow of the “Oozing-goo” as it rests on a horizontal surface.

In the True Solutions Vista, students are asked to participate as members of a talented design team at Rainbow Scapes, a design firm that specializes in liquid art displays for indoor use. The team is charged with the task of designing a permanent multicolored display for a client of the firm. To complete this assignment, the team has to investigate the necessary chemistry concepts of density, buoyancy, and viscosity. The final assessment will be a laboratory report that outlines the procedure to develop the new product.

Students may harbor many misconceptions about density, buoyancy, and viscosity. Teachers need to be cognizant of the misconceptions that students have and not assume that students understand the concepts based on their correct usage of formulas or terms. Merely introducing scientists’ definitions and formulas is not enough. Traditional hands-on approaches do not necessarily address the ideas and views that students bring to the class. For instance, a common misconception is that mass is the most important factor in determining whether an object will sink or float. Teachers need to determine what students think they already understand and then, using proper scientific principles, clarify the misconceptions.

NOTES

2 Integrated Physics and Chemistry Institute – Fall 2004 The Charles A. Dana Center at UT Austin 3

NOTES

Materials

Printed Materials Included in this Vista:

True Solutions Vista TEKS Correlation Chart

True Solutions Scenario

Examining Density investigation pages

Eureka! investigation pages

Ooze Factor investigation pages

Fluid Rainbow Assessment Task pages

Pretest/Posttest questions

Materials for the Teacher to Gather:

Each learning experience has a list of all necessary equipment and materials.

However, it is not the intention of TEXTEAMS to dictate the types and quantities of materials/equipment to use for the learning experiences. All the materials/equipment that are listed in the learning experiences are suggestions.

Teacher’s notes give specific instructions for areas where the author has experienced problems. Substitutions for materials/equipment should be based on local budgets, availability, and facilities.

Correlation to the National Science

Education Standards (NSES)

9–12 Abilities necessary to understand scientific inquiry

9–12 Understandings about scientific inquiry

9–12 Structure and properties of matter

K–12 Change, constancy, and measurement


NOTES


NOTES

True Solutions Scenario

You are a member of a talented design team at Rainbow Scapes, a design firm that specializes in liquid art displays for indoor use. This is a highly successful and profitable firm. A client has requested that the firm design a multicolored display using more than one medium. The art display will be made of glass blocks containing five colored layers and four beads suspended at different levels. Since the economy has been declining, this account is extremely important to your firm, and it is essential that a winning display be designed.

All of the design teams have been given the same challenge, with the winning team receiving a bonus. You and your team have no background in the chemistry concepts necessary to make this display. Therefore, your design begins with researching density, buoyancy, and viscosity by analyzing the results of a teacher demonstration.

Prepare a student journal entry for the teacher that describes your procedures to develop the liquid and bead display. To ensure sales, you must provide a quantitative explanation of your results and explain the relationship between density, buoyancy, and viscosity within your design. Your entries must also include the answers to each of the questions in your research (Learning

Experiences: Examining Density, Eureka!, and Ooze Factor).

NOTES


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NOTES

Integrated Physics and Chemistry Institute – Fall 2004

Examining Density

Learning Experience 1

Description:

This learning experience is designed to help students understand the TEKS concept of density.

Time Frame:


Materials:

Plastic aquariums, at least 4 L and 20 cm deep (2 for the teacher and 1 for each student group)

Distilled water 1 (to fill aquariums)

Snack-size, zipper-type plastic bag (1 for the teacher and 1 for each student group)

Glass marbles, same size and color (approximately 300)

12-ounce flat-bottomed plastic container with lid 2 (1 for the teacher and

1 for each student group)

12-ounce can of regular soda 3 (1 for the teacher and 1 for each student group)

12-ounce can of diet soda 3 (1 for the teacher and 1 for each student group)

Table salt 4 (170 g for the teacher)

Balance (1 per student group)

Overflow can (optional)

Graduated cylinder (1 for each student group)

Plastic film canisters with lids (2 for the teacher)

Graphing calculator (optional, 1 per student group)

Corn syrup (1 bottle for student observation)

Sucrose (sugar) (4 packets for the teacher and 1 packet per student group)

Aspartame 5 (2 packets for the teacher and 1 packet per student group)

Graph paper

Student laboratory notebook (1 per student)

Safety goggles (1 pair per student)

Laboratory apron (1 per student)

True Solutions Scenario (included in the Blackline Masters section at the end of this vista)

Examining Density investigation pages (included in the Blackline Masters section at the end of this vista)

The Charles A. Dana Center at UT Austin

NOTES

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NOTES Teacher notes:

1 Distilled water is preferred, but tap water allowed to sit undisturbed for 24 hours will suffice.

2 The size and shape of the container are critical to the learning experience.

The 12 oz flat-bottomed container is the same volume as the soda cans, but with a larger surface area.

3 Coke® and Diet Coke® are the preferred combination; Dr. Pepper® is not recommended.

4 Salt may be added to aquarium during class. However, this would have to be repeated for each class, thus requiring a large quantity of salt and water.

5 Any brand of aspartame can be used, including store brands. Check the label to be sure the product is aspartame.

Advance Preparation:

1. Place the teacher’s aquariums in the display position and fill both with distilled water.

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2. Prior to class, test sodas for buoyancy. If buoyancy difference is not notable, add water. It helps to use cold water and warm soda, but it may be necessary to use a larger aquarium or a stopped sink.

3. Add 170g of salt to one of the teacher aquariums.

4 Enough salt should be added to cause the regular soda can to float or bounce off the bottom. Test with soda cans in saltwater prior to class. Be sure to stir solution before each class demonstration.

4. Fill the snack-size, zipper-type plastic bags with glass marbles. The bags should be completely filled, which represents half of the necessary number of marbles needed for the investigation. Check the seal on each bag for leakage.

5. Add the same number of glass marbles to the plastic containers. Check the seal on each container for leakage.

6. Prepare copies of the True Solutions Scenario and Examining Density investigation pages for each student group.

Procedures:

SAFETY: Caution students about the danger of chemical splashes. Students must wear safety goggles and chemical-resistant aprons during this activity.

All chemicals must be disposed of properly. (See Texas Safety Standards for

Kindergarten–Grade 12).

1. Have students read the True Solutions Scenario.

2. Display the two filled aquariums, the two soda cans, the marble-filled bag, and the plastic container with marbles.


NOTES

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NOTES

Integrated Physics and Chemistry Institute – Fall 2004

3. Distribute the investigation pages. Ask students to predict whether each of the objects will sink or float when placed in the aquarium filled with water only. Have students record their predictions.

4. Tell students that you will place the objects in the aquarium filled with water only, one by one. Ask them to observe whether the object floats or sinks and, if it sinks, the rate at which it sinks.

Teacher note: Each object should remain in the aquarium after being released.

5. Gently place the can of regular soda in the aquarium. It should drop to the bottom of the aquarium. Have students record what they observe.

6. Next, gently place the can of diet soda in the aquarium. It should float. Have students record what they observe and write an explanation of what occurred.

7. Place the marble-filled bag slowly in the water.

Teacher note: Prior to releasing the bag, be sure all students are observing the difference in the rate of sinkage.

8. Place the marble-filled plastic container in the water.

Teacher note: For dramatic results, release the container under the water.

The container will bounce to the surface.

9. Remove the objects from the water and place in the saltwater aquarium. Keep the salt solution aquarium for the density calculation in the Eureka! Learning Experience.

Teacher note: If you add more salt to the water, you demonstrate to students that as the concentration of salt increases, the density of the saltwater solution increases.

10. Scientists claim that aspartame is sweeter than sugar, so it takes only a little aspartame to equal the taste of sugar. One packet of aspartame has the equivalent sweetness of 2 teaspoons of sugar. Put equal amounts of water into two film canisters. Add two packets of aspartame into one of the canisters, close and shake to dissolve. Add four packets of sugar to the second film canister, close and shake to dissolve. Place the two canisters in the aquarium that contains the fresh water. Have students observe the behavior of the two film canisters.

11. Have students complete the Examining Density investigation pages.

Formative Assessment: Observe students’ ability to predict the density of objects before making their observations and measurements.


NOTES

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Materials:

Can of regular soda, can of diet soda, snack-size plastic bag filled with marbles, aquarium, distilled water, plastic container filled with marbles, balance, graph paper, sucrose (sugar) packet, aspartame packet, corn syrup, student laboratory notebook, graphing calculator (optional), safety goggles, laboratory aprons

Procedures:

1. Predict the rankings of the mass, volume, and density of each object used in the teacher demonstration.

Predictions

Mass Volume Density

Least

Greatest

2. Measure with precision the mass, volume, and density of each object used in the teacher demonstration.

Construct three tables to record the data you collect on mass, volume, and density.

3. Write, in sequential order, the procedures you followed to measure the mass, volume, and density of the demonstration objects.

4. Describe the difference in ranking between the mass, volume, and density and your predictions.

5. Construct a graph of the data in each table. A graphing calculator may be used.

6. Using your graph, describe the relationship between the mass and volume of the densest object, and the least dense object.

7. Examine the plastic bag of marbles and the plastic container of marbles. The marbles represent what part of density?

8. What percentage of the plastic bag’s total volume (capacity) is composed of marbles? What occupies the remaining volume?

9. Compare and contrast all of the label information on the soda cans, the corn syrup, and the packets of sugar and aspartame, including nutrition contents, weight, and descriptions. Why are the contents listed in a certain order?

Record this information.

10. Study the molecular drawings of sucrose and aspartame shown below. Use your collected data to hypothesize how the molecular structure correlates to the density of the sodas.

Integrated Physics and Chemistry Institute – Fall 2004 The Charles A. Dana Center at UT Austin 11

Sucrose molecule

C

12

H

22

O

11

Aspartame molecule

C

14

H

18

N

2

O

5

11. Using your observations of the film canister demonstrations and your answer from the previous questions, what is one cause for the difference in density between the two types of soda?

12. What happened when the teacher added the soda cans to the saltwater aquarium? Provide a quantitative explanation.

13. Using the results of your investigation and any new information you have gathered, explain in your own words what is responsible for the difference in the behaviors of the four objects.

14. Define density.


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NOTES

Eureka!


Description:

This learning experience is designed to help students understand the TEKS concept of buoyancy.

Time Frame:


Materials:

Internet article on Archimedes’ discovery of density, which can be found at: http://www.mcs.drexel.edu/~crorres/Archimedes/Crown/

CrownIntro.html (1 per student)

Plastic aquariums, at least 4 L and 20 cm deep (2 for the teacher and 1 for each student group)

Distilled water (to fill each aquarium)

Snack-sized, zipper-type plastic bag (1 for the teacher and 1 for each student group)

Glass marbles, same size and color (approximately 300)

12-ounce flat-bottomed plastic container with lid (1 for the teacher and 1 for each student group)



Student laboratory notebook (1 per student)


Eureka! investigation pages (included in the Blackline Masters section at the end of this vista)


1. Prepare copies of the Eureka! investigation pages for each student group.

2. Make copies of the Internet article on Archimedes’ discovery of density, which can be found at: http://www.mcs.drexel.edu/~crorres/Archimedes/Crown/CrownIntro.html

, for each student.

Teacher note: TEXTEAMS does not have copyright privileges for the article.

Copies may be made for students to read, but must be collected and destroyed afterwards.


NOTES

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NOTES

Background Information for the Teacher:

In this learning experience, students examine the physical properties—weight, size, shape, etc.—of objects as those properties relate to the buoyancy of the objects. The story of Archimedes’ discovery is read in the article “Eureka,” giving students insight into the historic relevance of the force of buoyancy.

Refer to the vista background information for a more detailed explanation.

Procedures:

Safety: Caution students about the danger of chemical splashes. Students must wear safety goggles and chemical-resistant aprons during this activity. All chemicals must be disposed of properly. (See Texas Safety Standards for Kindergarten–Grade 12.)

1. Have students read the history of Archimedes’ discovery of density.

2. Review the data from Learning Experience 1, “Examining Density.”

Use any necessary equipment to provide documentation on why the four objects are or are not buoyant. Complete the Eureka! student investigation.

Teacher note: Students may need to repeat some of the procedures from the Examining Density Learning Experience.

Formative Assessment:

1. Observe students ability to answer Internet questions (brainteasers) found at http://www.pbs.org/wgbh/nova/lasalle/buoyancy.html

NOTES


14

Eureka!

Materials:

Internet article on Archimedes’ discovery of density, aquarium, distilled water, snack-size plastic bag, marbles, plastic container, student laboratory notebook, graphing calculator (optional), safety goggles, laboratory aprons

Procedures:

1. What did Archimedes discover?

2. How did he confirm his observations?

3. Review your student journal entries from the Examining Density Learning Experience. Use the data to explain how the addition of the salt to the water changed the buoyant force acting on the four objects.

4. Choose one of the four objects from “Examining Density.” Calculate the buoyant force of the fresh water on the object. Calculate the buoyant force of the salt water on the object. Explain why the buoyant forces differ.

Use your observations to support your answer.

5. How many marbles are in the bag? In the container? Manipulate the materials to determine how many marbles it takes to change the buoyancy of the marble-filled bag and the marble-filled container.

6. Write in sequential order the procedures you used in step 5.

7. Suggest another variable that determines if an object will float or sink. Use your observations to support your answer.

8. How does buoyancy relate to Newton’s Laws of Motion?

9. Internet Questions:

Submarine:

Boat:

Balloon:

10. Define buoyancy.


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14 Integrated Physics and Chemistry Institute – Fall 2004

Ooze Factor


Description:

This learning experience is designed to help students understand the TEKS concept of viscosity.

Time Frame:

55 minutes

Materials:

Sodium borate (Borax) (2 g per student group)

Graduated cylinder (1 per student group)

Water

Test tube (1 per student group)

Test tube rack (1 per student group)

Elmer’s ® school glue (1 bottle per student group)

250 mL beaker (1 per student group)

Food coloring (1 box of assorted colors for the teacher)

Stirring rods or wooden craft sticks (2 per student group)

Wax paper

Plastic drinking straw (1 per student group)

Metric ruler (1 per student group)

Balance (1 per student group)

Overflow cans (optional)

Clock or stopwatch (1 accessible to each student group)




Ooze Factor investigation pages (included in Blackline Masters section at the end of this vista)


Prepare copies of the Ooze Factor investigation pages for each student group.

Background Information for the Teacher:

Elmer’s ® school glue contains, among other ingredients, a polymer known as polyvinyl acetate, which at least in part accounts for its relatively high viscosity.

Sodium borate dissolves in water into sodium ions (Na+1) and borate ions


NOTES

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NOTES

(BO3-3). The borate ions act as cross-linking agents and hook the polyvinyl acetate chains together when they come into contact with each other.

This action results in a network of chains called a “cross-linked polymer,” represented in Figure 1. A fishing net is a common analogy for this type of network; however, a fishing net is too orderly and systematic. Most crosslinked polymers are more randomly networked.

�

��

��

� ��

��

��

��

Figure 1

Cross-linked polymer

The dilution of the glue is necessary to spread apart the polyvinyl acetate chains prior to cross-linking. If the polyvinyl acetate chains are too close, the cross-linking caused by the borate ions will be too extensive, and the fluid nature of the product will be lost. If the dilution is too great, the polyvinyl acetate chains will be too far apart, so little or no cross-linking will occur and the product will be too runny.

Teacher note: The emphasis of the learning experience is on the testing of the product, not the creation. However, students will notice that the quality of the product will vary from group to group. Therefore, it is important to compile class data as part of the conclusion.

Procedures:

Safety: Caution students about the danger of chemical splashes. Students must wear safety goggles and chemical-resistant aprons during this activity. All chemicals must be disposed of properly. (See Texas Safety Standards for Kindergarten–Grade 12.)

1. Have students complete the Ooze Factor investigation pages.

Formative Assessment: Observe students as they conduct the learning experience. Check student data at the completion of the investigation.

2. Compile class data from each test. Class discussion should focus on the forces and properties being investigated, and to what may have caused the differences between each group’s data. Emphasize the importance of controlling variables, and repeating investigations to obtain valid results.


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NOTES

3. Focus the discussion on the data collected from the density, buoyancy, and viscosity tests and the patterns within each group’s data. Students should notice that regardless of shape or size, density and buoyancy remain constant.

NOTES


Ooze Factor

Materials:

Sodium borate (borax), graduated cylinder, water, test tube, test tube rack, Elmer’s® school glue, food coloring, 250 mL beaker, stirring rods or craft sticks, plastic drinking straw, overflow can, clock or stopwatch, balance, metric ruler, wax paper, safety goggles, laboratory aprons, graphing calculator (optional)

Procedures:

SAFETY: Caution students about the danger of chemical splashes. Students must wear safety goggles and chemical-resistant aprons during this activity. All chemicals must be disposed of properly.

1. Prepare the Oozing-goo using the following recipe: a) Tape a piece of wax paper to laboratory workplace.

b) Measure 2.00 g of sodium borate and place it in a test tube. c) Add 15.0 mL of water, combining the water with the sodium borate by covering the end of test tube with the thumb and shaking the test tube vigorously for 15 seconds. d) After shaking, place the test tube in a rack, allowing any undissolved particles to settle. Record your observations.

e) Pour approximately 20 mL of Elmer’s® school glue into a 250 mL beaker.

f) Add 20 mL of water. g) Add 3 drops of food coloring (optional) to the glue. h) Mix thoroughly using the stirring rod/craft stick. The materials must be mixed thoroughly or the resulting substance will not be useable. i) Record your observations.

j) Pour the liquid portion of the sodium borate solution into the beaker of diluted glue. k) Leave any undissolved granules in the test tube. l) Stir the mixture in the beaker slowly for 15–20 seconds with a clean stirring rod/craft stick. m) Observe the mixture. Record your observations.

n) Remove as much of the “Oozing-goo” as possible from the beaker and place it in a pile on the wax paper on a laboratory table. o) Knead the Oozing-goo into a workable consistency.

2. Test the substance for the following properties, and record your observations in a data table.

a) Elasticity: Record what happens when the Oozing-goo is stretched quickly and when it is stretched slowly.

For each trial, measure and record the length of the Oozing-goo before it breaks into pieces.

b) Inflatability: Shape the Oozing-goo into a ball around one end of a drinking straw. Inflate the ball by blowing into the opposite end of the straw. Measure and record the size of the largest “balloon.”


c) Resilience: Shape the Oozing-goo into a ball and test its ability to bounce when dropped onto a tabletop.

Measure and record both the height from which it is dropped and the height at which it bounces.

d) Viscosity: Roll the Oozing-goo into a ball and place it on the table. Measure the diameter of the ball. Then, at one-minute intervals, measure the changes in diameter for five minutes. Divide the sample in half. Use the balance to make sure each half has the same mass. Repeat viscosity test for the each sample.

e) Buoyancy: Shape the Oozing-goo into a ball and measure the water’s buoyant force for the entire Oozinggoo sample. Flatten into a “pancake” and repeat procedure to find the buoyant force for this new shape. f) Density: Calculate the density of the entire Oozing-goo sample. Divide the sample in half. Use the balance to make sure each half has the same mass. Calculate the density of each sample.

Conclusions:

In a short paragraph, summarize your results, including what you learned about viscous substances. Include some observations and data. Compare and contrast your data with the data from another group. Discuss what may have caused the differences in the substances.


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NOTES

Fluid Rainbow

Assessment Task

Description:

This assessment task is designed to help students use the TEKS concepts of density, viscosity, and buoyancy to create a product.

Time Frame:

55 minutes

Materials:

Marking pencil (1 per student group)

250 mL beakers (2 per student group)

Water


Variety of containers (graduated cylinders, test tubes, flasks, etc.)

Variety of beads (plastic, metal, wax, etc.)

Food coloring (1 box of assorted colors for teacher)

Plastic or paper cups (4 per student group)

Hot plate (1 per student group)

Plastic pipette (1 per student group)

Waste container (1 per student group)

Student Laboratory Notebook (1 per student)



True Solutions Scenario (included in Blackline Masters section at the end of this vista)

Fluid Rainbow Assessment Task pages (included in Blackline Masters section at the end of this vista)

Additional materials based on student investigation:

Corn syrup (50 mL per student group)

Aspartame (5 packets per student group)

Sugar (5 packets per student group)

Table salt (50 g per student group)


Prepare copies of the Fluid Rainbow Assessment Task pages for each student group.


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NOTES

Procedures:

SAFETY: Safety goggles must be worn when working with any chemicals that could damage the eyes. Laboratory aprons must be worn to protect clothing. All chemicals must be disposed of properly. (See Texas Safety Standards for Kindergarten–Grade

12.)

1. Instruct students to reread the True Solutions Scenario.

2. Distribute the copies of the Fluid Rainbow Assessment Task pages to the students. Make sure students are aware of the safety precautions involved.

Teacher note: The students will not have the same designs since each group may color the liquids differently. Students who do not test the density of each liquid prior to making their design will end up with a dark liquid, in which it is obvious that denser liquids have been added on top of less dense liquids.

3. Have students complete the Fluid Rainbow Assessment Task pages.

4. Students will communicate their findings to the class in visual presentations and/or in a written report.

5. Use the assessment criteria checklist to assess each student’s work.

NOTES





Prepare a student journal entry for the teacher that describes your procedures to develop the liquid and bead display. To ensure sales, you must provide a quantitative explanation of your results and explain the relationship between density, buoyancy, and viscosity within your design. Your entries must also include the answers to each of the questions in your research (Learning Experiences: Examining Density, Eureka!, and Ooze Factor).


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Fluid Rainbow

Assessment Task

Materials:

Marking pencil, two 250 mL beakers, water, plastic or paper cups, hot plate, plastic pipette, table salt, sugar, corn syrup, aspartame, waste container, food coloring, variety of containers (graduated cylinders, test tubes, flasks, etc.), variety of beads (metal, plastic, wax, etc.), graphing calculator (optional), student laboratory notebook, safety goggles, laboratory aprons

SAFETY: Safety goggles must be worn when working with any chemicals that could damage the eyes. Laboratory aprons must be worn to protect your clothing. Dispose of chemicals properly.

Procedures:

Design and construct a colorful display of layered solutions and suspended beads. Your teacher must approve additional materials before you make your display.

List all additional materials selected and give their purpose: _______________________________________________

____________________________________________________________________________________________

Project Manager (teacher) sign off on the design:

__________________________________________

All observations, data, data analysis, and conclusions must be recorded in your laboratory notebook.

Conclusions:

Prepare a report that will accompany your display describing the liquids and beads in your display. Include explanations on why you chose your liquids and how you were able to maintain the liquids and beads in different layers.

Make a presentation of your display to the client (class). Use the Solutions Guide to score each display presentation and report.

23 Integrated Physics and Chemistry Institute – Fall 2004 The Charles A. Dana Center at UT Austin


True Solutions

Student Blackline Masters







26


Materials:

Can of regular soda, can of diet soda, snack-size plastic bag filled with marbles, aquarium, distilled water, plastic container filled with marbles, balance, graph paper, sucrose (sugar) packet, aspartame packet, corn syrup, student laboratory notebook, graphing calculator (optional), safety goggles, laboratory aprons

Procedures:

1. Predict the rankings of the mass, volume, and density of each object used in the teacher demonstration.

Predictions

Mass Volume Density

Least

Greatest

2. Measure with precision the mass, volume, and density of each object used in the teacher demonstration.

Construct three tables to record the data you collect on mass, volume, and density.

3. Write, in sequential order, the procedures you followed to measure the mass, volume, and density of the demonstration objects.

4. Describe the difference in ranking between the mass, volume, and density and your predictions.

5. Construct a graph of the data in each table. A graphing calculator may be used.


6. Using your graph, describe the relationship between the mass and volume of the densest object, and the least dense object.

7. Examine the plastic bag of marbles and the plastic container of marbles. The marbles represent what part of density?

8. What percentage of the plastic bag’s total volume (capacity) is composed of marbles? What occupies the remaining volume?

9. Compare and contrast all of the label information on the soda cans, the corn syrup, and the packets of sugar and aspartame, including nutrition contents, weight, and descriptions. Why are the contents listed in a certain order? Record this information.

10. Study the molecular drawings of sucrose and aspartame shown below. Use your collected data to hypothesize how the molecular structure correlates to the density of the sodas.

Sucrose molecule

C

12

H

22

O

11

Aspartame molecule

C

14

H

18

N

2

O

5

11. Using your observations of the film canister demonstrations and your answer from the previous questions, what is one cause for the difference in density between the two types of soda?


12. What happened when the teacher added the soda cans to the saltwater aquarium? Provide a quantitative explanation.

13. Using the results of your investigation and any new information you have gathered, explain in your own words what is responsible for the difference in the behaviors of the four objects.

14. Define density.


30

Eureka!

Materials:

Internet article on Archimedes’ discovery of density, aquarium, distilled water, snack-size plastic bag, marbles, plastic container, student laboratory notebook, graphing calculator (optional), safety goggles, laboratory aprons

Procedures:

1. What did Archimedes discover?

2. How did he confirm his observations?

3. Review your student journal entries from the Examining Density Learning Experience. Use the data to explain how the addition of the salt to the water changed the buoyant force action on the four objects.

4. Choose one of the four objects from “Examining Density.” Calculate the buoyant force of the fresh water on the object. Calculate the buoyant force of the salt water on the object. Explain why the buoyant forces differ.

Use your observations to support your answer.

5. How many marbles are in the bag? In the container? Manipulate the materials to determine how many marbles it takes to change the buoyancy of the marble-filled bag and the marble-filled container.

6. Write in sequential order the procedures you used in step 5.

7. Suggest another variable that determines if an object will float or sink. Use your observations to support your answer.

8. How does buoyancy relate to Newton’s Laws of Motion?


9. Internet Questions:

Submarine:

Boat:

Balloon:

10. Define buoyancy.


Ooze Factor

Materials:

Sodium borate (borax),graduated cylinder, water, test tube, test tube rack, Elmer’s® school glue, food coloring,

250 mL beaker, stirring rods or craft sticks, plastic drinking straw, clock or stopwatch, overflow can, balance, metric ruler, wax paper, safety goggles, laboratory aprons, graphing calculator (optional)

Procedures:


1. Prepare the Oozing-goo using the following recipe: a) Tape a piece of wax paper to laboratory workplace.

b) Measure 2.00 g of sodium borate and place it in a test tube. c) Add 15.0 mL of water, combining the water with the sodium borate by covering the end of test tube with

the thumb and shaking the test tube vigorously for 15 seconds. d) After shaking, place the test tube in a rack, allowing any undissolved particles to settle. Record your

observations.

e) Pour approximately 20 mL of Elmer’s® school glue into a 250 mL beaker.

f) Add 20 mL of water. g) Add 3 drops of food coloring (optional) to the glue. h) Mix thoroughly using the stirring rod/craft stick. The materials must be mixed thoroughly or the resulting

substance will not be useable. i) Record your observations.

j) Pour the liquid portion of the sodium borate solution into the beaker of diluted glue. k) Leave any undissolved granules in the test tube. l) Stir the mixture in the beaker slowly for 15–20 seconds with a clean stirring rod/craft stick. m) Observe the mixture. Record your observations.

n) Remove as much of the “Oozing-goo” as possible from the beaker and place it in a pile on the wax paper on a laboratory table. o) Knead the Oozing-goo into a workable consistency.

2. Test the substance for the following properties, and record your observations in a data table.

a) Elasticity: Record what happens when the Oozing-goo is stretched quickly and when it is stretched slowly.

For each trial, measure and record the length of the Oozing-goo before it breaks into pieces.

b) Inflatability: Shape the Oozing-goo into a ball around one end of a drinking straw. Inflate the ball by

blowing into the opposite end of the straw. Measure and record the size of the largest “balloon.”


c) Resilience: Shape the Oozing-goo into a ball and test its ability to bounce when dropped onto a tabletop.

Measure and record both the height from which it is dropped and the height at which it bounces.

d) Viscosity: Roll the Oozing-goo into a ball and place it on the table. Measure the diameter of the ball. Then,

at one-minute intervals, measure the changes in diameter for five minutes. Divide the sample in half. Use

the balance to make sure each half has the same mass. Repeat viscosity test for the each sample.

e) Buoyancy: Shape the Oozing-goo into a ball and measure the water’s buoyant force for the entire Oozing-

goo sample. Flatten into a “pancake” and repeat procedure to find the buoyant force for this new shape. f) Density: Calculate the density of the entire Oozing-goo sample. Divide the sample in half. Use the balance

to make sure each half has the same mass. Repeat density test for the each sample.

Conclusions:

In a short paragraph, summarize your results, including what you learned about viscous substances. Include some observations and data. Compare and contrast your data with the data from another group. Discuss what may have caused the differences in the substances.







34

Fluid Rainbow

Assessment Task

Materials:

Marking pencil, 250 mL beakers, water, plastic or paper cups, hot plate, plastic pipette, table salt, sugar, corn syrup, aspartame, waste container, food coloring, variety of containers (graduated cylinders, test tubes, flasks, etc.), variety of beads (metal, plastic, wax, etc.), graphing calculator (optional), student laboratory notebook, safety goggles, laboratory aprons


Procedures:

Design and construct a colorful display of layered solutions and suspended beads. Your teacher must approve additional materials before you make your display.

List all additional materials selected and give their purpose: _______________________________________________

____________________________________________________________________________________________

Project Manager (teacher) sign off on the design:

__________________________________________

All observations, data, data analysis, and conclusions must be recorded in your laboratory notebook.

Conclusions:

Prepare a report that will accompany your display describing the liquids and beads in your display. Include explanations on why you chose your liquids and how you were able to maintain the liquids and beads in different layers.

Make a presentation of your display to the client (class). Use the Solutions Guide to score each display presentation and report.

35 Integrated Physics and Chemistry Institute – Fall 2004 The Charles A. Dana Center at UT Austin



TRUE SOLUTIONS

Pre– and Post–Test

1. During an experiment, a student pours equal volumes of four liquids onto an inclined plane. Which liquid will reach the bottom of the board first?

A

The liquid with the greatest viscosity.

B

The liquid with the greatest mass.

C

The liquid with the lowest temperature.

D

The liquid with the lowest density.

Fluid

W

X

Y

Z

Mass

22 g

28 g

16 g

50 g

Volume

10 mL

7 mL

5 mL

10 mL

2. According to the data above, which one of these fluids is the least dense?

A

W

B

X

C

Y

D

Z

��

��

��

��

��

��

3. The density of corn syrup is 1.38 g/cm syrup, what will happen?

3 . If a pencil eraser with the dimensions of

0.5 cm x 3.00 cm x .5 cm and a mass of 16.08 g is placed into a beaker filled with corn

A The eraser will float on the corn syrup.

B The eraser will dissolve into the corn syrup.

C The eraser will sink to the bottom of the beaker.

D The eraser will stick to the side of the beaker.

4. The buoyant force acting on a helium-filled balloon lessens as the balloon moves to a higher altitude. Which of the following is the best explanation for this phenomenon?

A The force of gravity becomes greater at higher altitudes.

B The air at higher altitudes is less dense.

C The helium atoms gain mass as the balloon moves upwards.

D The temperature is lower at higher altitudes.

5. Liquid water is more dense than ice because—

A liquid water molecules have more mass.

B when ice melts there is an increase in the number of water molecules.

C more liquid water molecules will fit into a container with a specific volume.

D a chemical change occurs when water freezes which causes an increase in mass.

6. Petroleum geologists and engineers often pump salt water down into an oil well. This action helps to increase oil production because—

A salt water mixes with the oil and makes it less viscous.

B salt water exerts a buoyant force on the oil causing the oil to rise.

C salt water is less dense than the oil causing the oil to sink.

D salt water coats the pipes and creates a frictionless surface.

7. Four solid objects are made from the same exact plastic material. The density of the plastic material is 0.95 g/cm 3 . Based on the information above, which of the following statements will happen when all four objects are placed in a large container of distilled water?

A Only objects W and X will float.

B Only object W will float.

C All of the objects will float.

D All of the objects will sink.

8. Students are conducting an investigation on viscosity. They place 50 mL of corn syrup, at room temperature, in a graduated cylinder. A marble is then placed into the cylinder, and the time it takes to sink through the corn syrup is recorded. Which of the following statements would allow the students to change the viscosity of the corn syrup?

A Warm the corn syrup above room temperature.

B Use less than 75 mL of corn syrup in the graduated cylinder.

C Allow the corn syrup to “rest” after pouring it into the graduated cylinder.

D Add 50 grams of table sugar to the corn syrup.

9. Why would it be easier to lift a large object in water than to lift that same object on land?

A The force of gravity behaves differently in water.

B The viscosity of water increases when a solute is added to it.

C The object weighs more on land because of an increase in its density.

D The water provides a buoyant force, which makes the object seem to have less weight.

10. A 19.8 g piece of metal is placed in a graduated cylinder and displaces 2.53 mL of water.

What is the density of this metal?

A 0.128 g/mL

B 7.83 g/mL

C 17.27 g/mL

D 22.33 g/mL

True Solutions

1. D

2. A

3. C

4. B

5 C

6. B

7. C

8. A

9. D

10. B

Answer Key

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Chemistry Vista

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True Solutions

Student Blackline Masters

Sucrose molecule

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TRUE SOLUTIONS

Pre– and Post–Test

1. During an experiment, a student pours equal volumes of four liquids onto an inclined plane. Which liquid will reach the bottom of the board first?

The liquid with the greatest viscosity.

The liquid with the greatest mass.

The liquid with the lowest temperature.

The liquid with the lowest density.

2. According to the data above, which one of these fluids is the least dense?

W

X

Y

Z

True Solutions

Answer Key

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Support

True Solutions NOTES Chemistry Vista Overview

Chemistry Vista

Sucrose molecule

Aspartame molecule

True Solutions

Student Blackline Masters

Sucrose molecule

Aspartame molecule

TRUE SOLUTIONS

Pre– and Post–Test

1. During an experiment, a student pours equal volumes of four liquids onto an inclined plane. Which liquid will reach the bottom of the board first?

The liquid with the greatest viscosity.

The liquid with the greatest mass.

The liquid with the lowest temperature.

The liquid with the lowest density.

2. According to the data above, which one of these fluids is the least dense?

W

X

Y

Z

True Solutions

Answer Key

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