VISCOSITY and FALL SPEED

After carrying out these experiments, students should be able to:

Define viscosity.

Calculate speed of a sinking or floating object, using collected distance and time data.

Infer viscosity of a material by noting the speed at which objects float or sink in the material.

Relate viscosity to the slow or rapid movement of Earth materials such as the atmosphere, oceans, and mantle.

Form a hypothesis.

Design an experiment to test the effect of a chosen variable on sinking or floating speed.

Conduct an experiment with appropriate controls.

Record data in an organized manner.

Share results with classmates, using diagrams and oral presentations.

This set of laboratory-based lessons is designed for 13- to 14-year-old students in an eighth grade, heterogeneously grouped classroom environment. Class size is approximately 22 – 24 students. Students with learning disabilities are grouped in a co-taught classroom, where the science teacher is assisted by special education personnel.

The initial activity is designed to take one 55-minute class period. The second activity involving changing the size of steel balls would take an additional 55-minute class. Further extensions would take additional periods, depending on student preparedness and intricacy of experiments they design. It might be wise to allow a non-lab school day between experiments for processing and homework time.

Before beginning this activity, students should have an understanding of speed as a relationship of distance over time. A brief review of the formula for calculating speed, and appropriate units, might be necessary at the start of the first class.

Standard laboratory equipment such as graduated cylinders and rulers will be used for this lab. In addition, common household fluids (honey, corn syrup, laundry detergent) will also be needed. Steel balls of known diameter should be purchased as well. For extension activities, samples of other materials (wood, plastic, etc.) may be purchased or brought in by students.

Background

These lessons will be conducted at the start of a unit on the universe and the solar system, so that students enter the unit with an understanding of viscosity and slow convective motion. Throughout the unit, students will apply the concepts from these lessons to their understanding of planetary formation. Later in the year, students will revisit the concepts as they study mantle motion and plate tectonics.

In-Class Activities

Liquid Viscosity Lab: Teaching Activities (Microsoft Word 2007 (.docx) 17kB Jul27 11)

At Home Assignments

See attached document.

Materials

See attached document.

Standards

In conducting these experiments, students will practice the skills of Inquiry, Experimentation, and Design, as described in the Massachusetts Science and Technology/Engineering Curriculum Frameworks for grades 6 – 8:

Formulate a testable hypothesis.

Design and conduct an experiment specifying variables to be changed, controlled, and measured.

Select appropriate tools and technology (e.g., calculators, computers, thermometers, meter sticks, balances, graduated cylinders, and microscopes), and make quantitative observations.

Present and explain data and findings using multiple representations, including tables, graphs, mathematical and physical models, and demonstrations.

Draw conclusions based on data or evidence presented in tables or graphs, and make inferences based on patterns or trends in the data.

Communicate procedures and results using appropriate science and technology terminology.

Offer explanations of procedures, and critique and revise them.




Applicable Massachusetts Curriculum Frameworks content standards for physical and Earth science include:

Describe how the movement of the earth's crustal plates causes both slow changes in the earth's surface (e.g., formation of mountains and ocean basins) and rapid ones (e.g., volcanic eruptions and earthquakes).

Explain and give examples of how the motion of an object can be described by its position, direction of motion, and speed.

Observe students as they work to determine appropriate timing. Materials management may take up more time than expected. Data evaluation and discussion can wait until the next day if class periods are too short to allow completion.

Assign students to mixed groups and try to balance gender, work ethic, and skills in math and leadership.

Have special education teachers work with students who need extra help at constructing data tables, graphs, etc..

Carefully place students with special needs or social issues so that their groupmates allow them to be successful.

To make the project more inquiry-based from the start, allow students to develop their own system for determining viscosity. This requires flexibility in use of class time, gathering of materials, etc..

Formative assessments should be done throughout the activities. Teachers should circulate and talk to
student groups as they plan and carry out the activity, questioning them about the purpose of their steps, the data table set-up, consistent procedures, etc.. Students will also be working in groups, which allows individual students to check the work of other students and offer suggestions.

Summative assessment could be done in many formats (see resources):
- Standard lab report write-ups
- Oral presentations by groups
- Peer evaluation of presentations

Links to similar activities, or labs using a different means of measuring viscosity (all working as of July 27, 2011):
http://www.biotechlearn.org.nz/focus_stories/honey_to_heal/experiment_the_viscosity_of_honey
https://www.planetseed.com/node/19136
http://www.youtube.com/watch?v=oHxNnnde9lc
http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_p055.shtml
http://www.youtube.com/watch?v=OW9hBQBsG84
http://dwb4.unl.edu/chemistry/smallscale/SS070.html

*Note: Some of these activities measure viscosity by "racing" the fluids rather than dropping things through them – which may be more manageable for large groups of students.

Samples of standard lab report write-ups. (I tend to modify these depending on time, focus, learning outcomes, etc.)
http://www.biologycorner.com/worksheets/labreport.html
http://www.wku.edu/3kinds/dmlabmain.html