March/April 2017 – Vol. 29 No. 6

Density Lesson

Posted: Tuesday, September 3rd, 2013

by Jeff Orlinsky

Chemistry and physical science teachers, here is a lesson on density.  It can be used with grades 10 to 12, but with some modifications it may also work with 8th or 9th grade.  This is a modification of a lab from West Catholic High School Archdiocese of Philadelphia, with references from Kenneth E. Kolb and Doris K. Kolb, Bradley University, Peoria, IL 61625 Journal of Chemical Education.

Grades: 10 – 12

Subjects: Chemistry, Earth Sciences, Physics, Physical Science, Environmental Science

Topics: Density, polymers recycling, solution preparation.

Duration: 20 min Prep + 1 hour Activity + 1 hour Post

Setting: Classroom

Materials:

  • Appropriate glassware for mixing and sharing solutions
    • Seven (7) 250-mL beakers, graduated cylinders, stirring rod, long forceps
  • NaCl 90% Ethanol, 70% isopropanol, Karo syrup, monosodium phosphate, H2O
  • Different types of plastics (see below).
  • Hole punch

Activity:

On TV, plastics from milk, soda and other food containers are shown recycled into park benches and plastic posts. However, for some uses the recycled plastic must all be the same type of material. Many municipalities have days when they pick up scrap metal, glass and plastics and some communities are urged to put the three types of materials in separate containers, but sometimes consumers sort the objects into the wrong category of waste. So, how is the waste accurately separated for recycling? Magnets can remove some metals from a moving conveyer belt.  Other metals and glass of various colors are sorted by hand.

Advertisement

Advertisement

And, how can the plastics be separated? Magnets cannot be used. Visual inspection, even with the aid of recycling codes, is tedious. Can density help?

This lab starts with a demonstration, allows time for students to practice with the materials and apparatus, and ends with the students designing and running an experiment to identify unknown plastics.

This table identifies different polymers and their store-bought products.

Orlinsky_Table1

Table of different Polymers identified by densities and solution preparation

Orlinsky_Table2

Teacher Demonstration:

  • Apparatus:  seven (7) 250-mL beakers, graduated cylinders, stirring rod, long forceps.
  • Prepare the seven (7) beakers with the different density solutions according to the chart above.
  • Demonstrate how samples of plastic sink or float in the appropriate liquids.
  • Discuss reasons why the plastics float or sink.

Guided Student Practice:

  • Apparatus: 250-mL beaker, forceps
  • Materials: distilled water, access to beakers previously used in demonstration, two (2) plastic samples (with coded identity) for each group
  • Procedure: (DONE IN GROUPS OF 4)
    • Assign two (2) different types of plastic to each pair in groups of four (4).
    • Examine the plastics and record its code and its appearance.
      • Sample Code __________________ Sample Code __________________
      • Appearance ___________________ Appearance ___________________
    • Using the solutions, observe if the plastic to floats or sinks.
    • Verify that the plastic you have floats or sinks in the correct solution.

Student Independent Practice/Lab:

  • Objective:  Each group must predict and design a way to identify the plastics using only the known density solutions.
  • Instructions for students: Plan how to use the apparatus and materials you have been assigned to identify the pieces of plastic.
  • Students have access to the beakers from the previous demonstration, plus distilled water and normal laboratory equipment.
  • Each team executes the identification plan for the pieces of plastic they have been given.
  • To add a challenge:  all known solutions must be in a single container and students cannot have 7 beakers to test all solutions.

Use of models:

  • Using words, pictures or a physical model, show how a municipality could separate the large volume of waste plastics it collects.

Written by Jeff Orlinsky

Jeff Orlinsky

Jeff Orlinsky teaches science at Warren High School and is CSTA’s High School Director.

Leave a Reply

LATEST POST

CSTA Endorses March for Science

Posted: Monday, March 27th, 2017

The California Science Teachers Association (CSTA) stands with our science and science education colleagues in endorsing the March For Science and its associated activities.

The decision by the CSTA Board of Directors to support the March for Science was based on the understanding that this is an opportunity to advocate for our mission of high quality science education for all and to advance the idea that science has application to everyday life, is a vehicle for lifelong learning, and the scientific enterprise expands our knowledge of the world around us. The principles and goals of the March for Science parallel those of CSTA to assume a leadership role in solidarity with our colleagues in science and science education and create an understanding of the value of science in the greater community. CSTA believes that the integrity of the nature of science and that the work of scientists and science educators should be valued and supported. We encourage your participation to stand with us.

There are over 30 satellite marches planned for the April 22, 2017 March for Science in California (to find a march near you, click on “marches” in the upper right of the main page, select “satellite marches” and use the search feature). We encourage members who participate in the March for Science to share their involvement and promotion of science and science education. Feel free to promote CSTA on your signs and banners. For those on social media, you may share your involvement via Twitter, @cascience and our Facebook groups.

Written by California Science Teachers Association

California Science Teachers Association

CSTA represents science educators statewide—in every science discipline at every grade level, Kindergarten through University.

California Science Curriculum Framework Now Available

Posted: Tuesday, March 14th, 2017

The pre-publication version of the new California Science Curriculum Framework is now available for download. This publication incorporates all the edits that were approved by the State Board of Education in November 2016 and was many months in the making. Our sincere thanks to the dozens of CSTA members were involved in its development. Our appreciation is also extended to the California Department of Education, the State Board of Education, the Instructional Quality Commission, and the Science Curriculum Framework and Evaluation Criteria Committee and their staff for their hard work and dedication to produce this document and for their commitment to the public input process. To the many writers and contributors to the Framework CSTA thanks you for your many hours of work to produce a world-class document.

For tips on how to approach this document see our article from December 2016: California Has Adopted a New Science Curriculum Framework – Now What …? If you would like to learn more about the Framework, consider participating in one of the Framework Launch events (a.k.a. Rollout #4) scheduled throughout 2017.

The final publication version (formatted for printing) will be available in July 2017. This document will not be available in printed format, only electronically.

Written by California Science Teachers Association

California Science Teachers Association

CSTA represents science educators statewide—in every science discipline at every grade level, Kindergarten through University.

Call for CSTA Awards Nominations

Posted: Monday, March 13th, 2017

The 2017 Award Season is now open! One of the benefits of being a CSTA member is your eligibility for awards as well as your eligibility to nominate someone for an award. CSTA offers several awards and members may nominate individuals and organizations for the Future Science Teacher Award, the prestigious Margaret Nicholson Distinguished Service Award, and the CSTA Distinguished Contributions Award (organizational award). May 9, 2017 is the deadline for nominations for these awards. CSTA believes that the importance of science education cannot be overstated. Given the essential presence of the sciences in understanding the past and planning for the future, science education remains, and will increasingly be one of the most important disciplines in education. CSTA is committed to recognizing and encouraging excellence in science teaching through the presentation of awards to science educators and organizations who have made outstanding contributions in science education in the state and who are poised to continue the momentum of providing high quality, relevant science education into the future. Learn More…

Written by California Science Teachers Association

California Science Teachers Association

CSTA represents science educators statewide—in every science discipline at every grade level, Kindergarten through University.

Call for Volunteers – CSTA Committees

Posted: Monday, March 13th, 2017

Volunteer

CSTA is now accepting applications from regular, preservice, and retired members to serve on our volunteer committees! CSTA’s all-volunteer board of directors invites you to consider maximizing your member experience by volunteering for CSTA. CSTA committee service offers you the opportunity to share your expertise, learn a new skill, or do something you love to do but never have the opportunity to do in your regular day. CSTA committee volunteers do some pretty amazing things: Learn More…

Written by California Science Teachers Association

California Science Teachers Association

CSTA represents science educators statewide—in every science discipline at every grade level, Kindergarten through University.

A Friend in CA Science Education Now at CSTA Region 1 Science Center

Posted: Monday, March 13th, 2017

by Marian Murphy-Shaw

If you attended an NGSS Rollout phase 1-3 or CDE workshops at CSTA’s annual conference you may recall hearing from Chris Breazeale when he was working with the CDE. Chris has relocated professionally, with his passion for science education, and is now the Executive Director at the Explorit Science Center, a hands-on exploration museum featuring interactive STEM exhibits located at the beautiful Mace Ranch, 3141 5th St. in Davis, CA. Visitors can “think it, try it, and explorit” with a variety of displays that allow visitors to “do science.” To preview the museum, or schedule a classroom visit, see www.explorit.org. Learn More…

Written by Marian Murphy-Shaw

Marian Murphy-Shaw

Marian Murphy-Shaw is the student services director at Siskiyou County Office of Education and is CSTA’s Region 1 Director and chair of CSTA’s Policy Committee.