May/June 2017 – Vol. 29 No. 7

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.

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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.

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Participate in Chemistry Education Research Study, Earn $500-800 Dollars!

Posted: Tuesday, May 9th, 2017

WestEd, a non-profit educational research agency, has been funded by the US Department of Education to test a new molecular modeling kit, Happy Atoms. Happy Atoms is an interactive chemistry learning experience that consists of a set of physical atoms that connect magnetically to form molecules, and an app that uses image recognition to identify the molecules that you create with the set. WestEd is conducting a study around the effectiveness of using Happy Atoms in the classroom, and we are looking for high school chemistry teachers in California to participate.

As part of the study, teachers will be randomly assigned to either the treatment group (who uses Happy Atoms) or the control group (who uses Happy Atoms at a later date). Teachers in the treatment group will be asked to use the Happy Atoms set in their classrooms for 5 lessons over the course of the fall 2017 semester. Students will complete pre- and post-assessments and surveys around their chemistry content knowledge and beliefs about learning chemistry. WestEd will provide access to all teacher materials, teacher training, and student materials needed to participate.

Participating teachers will receive a stipend of $500-800. You can read more information about the study here: https://www.surveymonkey.com/r/HappyAtoms

Please contact Rosanne Luu at rluu@wested.org or 650.381.6432 if you are interested in participating in this opportunity, or if you have any questions!

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.

2018 Science Instructional Materials Adoption Reviewer Application

Posted: Monday, May 8th, 2017

The California Department of Education and State Board of Education are now accepting applications for reviewers for the 2018 Science Instructional Materials Adoption. The application deadline is 3:00 pm, July 21, 2017. The application is comprehensive, so don’t wait until the last minute to apply.

On Tuesday, May 9, 2017, State Superintendent Tom Torlakson forwarded this recruitment letter to county and district superintendents and charter school administrators.

Review panel members will evaluate instructional materials for use in kindergarten through grade eight, inclusive, that are aligned with the California Next Generation Science Content Standards for California Public Schools (CA NGSS). 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.

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Posted: Monday, May 8th, 2017

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To more closely examine some of the early successes and challenges experienced by the Early Implementer LEAs, Achieve interviewed nine of the ten participating districts and compiled that information into two resources, focusing primarily on professional learning and instructional materials. 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.

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Posted: Monday, May 8th, 2017

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Written by NGSS Early Implementer

NGSS Early Implementer

In 2015 CSTA began to publish a series of articles written by teachers participating in the NGSS Early Implementation Initiative. This article was written by an educator(s) participating in the initiative. CSTA thanks them for their contributions and for sharing their experience with the science teaching community.

Celestial Highlights: May – July 2017

Posted: Monday, May 8th, 2017

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Written by Robert Victor

Robert Victor

Robert C. Victor was Staff Astronomer at Abrams Planetarium, Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs, CA. Robert is a member of CSTA.