Go With the Flow -
Flowability Tests of Various Liquids

Developers:

Treva A. McLaughlin
Wissahickon School District
Shady Grove Elementary School
Ambler, PA 19002

Michael J. Gavaghan
Dr. Peter A. Yarnell
Rohm and Haas Company
Spring House, PA

Grade
Levels:

4th Grade Enrichment Students

Discipline:

Physical Science

Goals:

1. To broaden students' knowledge and understanding of liquids
2. To develop an awareness of the varying viscosities of liquids
3. To introduce or further develop an understanding of the Scientific Method
4. To develop an understanding of basic safety guidelines that will be followed

Specific
Objectives:

• Students will conduct experiments using liquids of differing viscosities.
• Students will observe differences in flow rates.
• Students will draw conclusions based on these differences.
• Students will follow the Scientific Method in their experimentation.
• Students will help to formulate and follow safety guidelines.

Background:

All liquids flow. Liquids also offer some resistance to flow, due to friction between layers of fluid. This resistance, called viscosity, is related to the size and complexity of the molecules in a liquid.

Viscosity measurements can furnish valuable information on the molecular weight and on the size and shape of the molecules being studied. This information is useful in the development of products as far ranging as syrups, ketchups, and shampoos. It is critically important in the development and testing of motor oils.

Viscosity can be measured in a number of ways. It is most conveniently measured by observing the flow of a liquid through a capillary. The rising bubble method measures the rate at which an air bubble rises through a given liquid. In the falling ball method, a metal or glass ball of known density is dropped through the liquid and its time of fall is noted.

Vocabulary:

Liquid - form of matter between gas and solid, a characteristic of which is its ability to flow, depending largely on its viscosity

Viscosity - the internal resistance to flow exhibited by a fluid

Density - basis of comparison for solids and liquids

Flow - 1. the motion characteristic of fluids, 2. to move with a continual change of place of the constituent particles (i.e. molasses)

Air bubble - a small globule, typically hollow and light as a small body of air within a liquid

Hypothesis - a tentative assumption made in order to draw out and test its logicaland empirical (observable) consequences

Isopropyl alcohol - an organic solvent of similar density to water

Simultaneous - occurring at the same time

Molecule - a combination of two or more atoms

Materials:

Plastic tubing (ex. straws from Big Gulp� drink cups.)
Plugs / stoppers (i.e. rubber squeeze bulbs from eye droppers)
Timers or stop watches
Funnels
Liquids i.e.

• Water
• Various brands of shampoo (Johnson's Baby Shampoo�, Alberto VO 5�)
• Isopropyl alcohol *To Be Used With Caution*
• Karo� corn syrup
• Pancake syrup
• Vegetable oil
• Motor oil

Teacher Note:
Much of the emphasis of the following lessons will be on teaching the concept of and understanding the importance of the Scientific Method. Also, safety procedures will be dealt with as a large component of the teaching.

It is hoped that both of these concepts will be useful in other science projects in the regular classroom and applied as life-long learning.

Procedure:

Safety Guidelines:

1. Present the idea of safety procedures for science experiments.
2. Ask students to brainstorm, individually or in small groups, their ideas of important rules to follow.
3. Compile group list on chart/board.
4. Examine, discuss generated list.
5. Distribute "Safety Guidelines" found on the inside of the back cover.
6. Note any topics that were not included on class list.
7. Explain any guidelines that are unclear.
8. Stress positive reasons for precautions.

Materials selected for this project are deemed to be relatively "safe".
Some materials are suggested for teacher use only.
If other materials are substituted, please consider the safety implications.

Scientific Method:

Present the steps of the Scientific Method:

1. Identify and state the problem.
2. Collect as much information as possible about the problem.
3. Form the hypothesis.
4. Test the hypothesis.
5. Draw conclusions about the hypothesis.
6. Report the conclusions so that other scientists can test the hypothesis.

Discuss reasons for each step and universality of the Scientific Method.

Introduction
to Experiments:

1. Display various liquids (i.e. shampoo, corn syrup, vegetable oil, alcohol, water, motor oil.)
2. Discuss commonality, similarities, differences in liquids.
3. State objective of the lesson. (Testing flowability to determine differences in viscosity of various liquids)
4. Brainstorm, as a class or in small groups, expectations / hypotheses concerning experiments to be performed.
5. Record ideas (individually or as a group.)

Sample Liquids

Suggested questions /activities -

 
• List as many "fast moving" liquids as you can.
• List as many "slow moving" liquids as possible.
• Which liquid do you think will flow the fastest?
• Which will move the slowest?
• Will any two move at the same speed? Why do you think so?
• Did you base your hypothesis on "looks" of the liquid? - previous experience with or knowledge about the liquid?

Rising Bubble Test

 
1. Divide class into small working groups.
2. Within each group, divide responsibilities.
3. Distribute necessary materials to each group. (4 plastic tubes - use tubes with like or very similar diameters and lengths, 8 stoppers, funnel, 4 liquids to be tested - i.e. shampoo, water, vegetable oil, pancake syrup, motor oil)
4. Measure and mark tube at 2.3 cm from end (to leave space for air bubble.)
5. Plug bottom of tube.
6. Fill tube to the mark with one of the liquids. (Or teacher may choose to distribute pre-filled tubes.)
7. Cap tube.

   ** Option: Distribute liquid-filled tubes.

8. Invert tube and simultaneously start stop watch or timer. (Note: Hold end of tube to avoid influencing temperature with heat of hand. Hold the tube upright; do not tilt tube.)
9. Record time that bubble reaches edge of top stopper.
10. Repeat and time test two more times.
11. Find average time and record.
12. Repeat procedure using each liquid to be tested.
13. Evaluate your results and record your conclusions.
14. Share / compare your results with other groups.

Suggested Questions:

• What similarities did you find among liquids? Differences?
• How do your results compare to the results of other groups?
• Did you notice similarities among samples of a given liquid? Differences?
• What can you infer from your findings?

Falling Ball Test (Teacher demonstration suggested) Additional materials needed:

 
• graduated cylinder (or any clear cylinder of sufficient diameter to accommodate balls)
• small rubber or glass balls (diameter approx. 9 mm., approx. 10)

** Caution: Be sure that balls are not so heavy as to break glass cylinder.

 
1. State objective of the lesson. (Flowability testing using falling ball method to determine differences in viscosity of various liquids)
2. Formulate hypotheses concerning experiment to be performed.
3. Record ideas individually or as a group.
4. Assemble materials - graduated cylinder, small rubber or glass balls, liquids to be tested, timer
5. Mark cylinder one-third and two-thirds of the way from top (or use inscribed measurements) in order to time rate of fall between two points. (Speed of ball needs to become constant before time test is initiated.)
6. Fill cylinder with first test liquid.
7. Drop ball (or have student drop ball) into center of cylinder.
8. Start timer when ball reaches one-third mark. (Angle of view is important.)
9. Stop timer when ball reaches two-thirds mark.
10. Record results.
11. Repeat test two more times.
12. Fill another cylinder with second liquid to be tested.
13. Repeat procedure.
14. Evaluate your results and record your conclusions.

Assessment:

1. Ask students to define the term and explain the concept of viscosity. Have students discuss variations in viscosities and list reasons why viscosity / flowability is important.
2. Check for understanding of the Scientific Method as students use it during experiments.
3. Ask students to list and explain reasons for five or more safety procedures.

Extensions:

1. Alternative procedure

   Given the above stated objectives, allow students to select the materials and determine the methods necessary to meet the objectives. Students will need to decide on what variables to control and what equipment will best serve their purpose as a research scientist must do.

2. Vary temperatures of liquids in tubes by immersing them in ice or cold water / hot or warm water. Conduct rising bubble experiment. Note differences.
3. Calculate volume of tubes, glass cylinder.
4. Give suggestions for follow-up activities at home.

Additional Liquid Learning activities

 
1. pH Testing using Red Cabbage Indicator (see Cobb, Vicki, Science Experiments You Can Eat, Scholastic, New York, 1972, p.25)
2. Diffusion activity (Wonder Science, vol. 3, number 4 )
3. Surface tension testing (see Allison, Linda and Katz, David, Gee,Wiz!, Yolla Bolly Press, Covelo, California, 1983, p. 50)
4. Stacking liquids (see The Density Tower - Project LABS 1990)

References:

Fisher Scientific Company, Pittsburgh, PA, 1991-92 Catalogue Kittsley, Scott, Physical Chemistry, New York, Barnes and Noble, Inc., 1963 Salzburg, Hugh W. et.al., Physical Chemistry, Academic Press, New York, 1969, p 112-119

Shugar, Gershon J. et. al, Chemical Technicians� Ready Reference Handbook, McGraw Hill, New York, 1981, p.210-218

Test Correlation: