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IRC: Physical Properties of Metals, Nonmetals, and Metalloids

Page history last edited by Hye Jeong Kim 14 years, 4 months ago

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NOTE: For information on the Periodic Table, see IRC: The Periodic Table

 

Current TEKS:  

6.7 B:  classify substances by their physical and chemical properties. 

7.7 B:  describe physical properties of elements and identify how they are used to position an element on the periodic table 

 

Future TEKS: 

6.2 D:  construct tables and graphs, using repeated trials and means, to organize data and identify patterns

6.6 A:  compare metals, nonmetals, and metalloids using physical properties such as luster, conductivity, or malleability

  

Scope and Sequence: 

Aldine: Grade 6; Grade 7, 2nd 6 weeks               Cy-Fair: Grade 6, 1st 6 weeks

  

Big Ideas: 

Physical properties of substances are properties that are observed without any chemical changes made to the substance.  Some examples are phase, luster, malleability, ductility, conductivity, density, and boiling point.  These properties are part of criterion used to classify matter into metals, nonmetals and metalloids.

 

Physical properties of metals, nonmetals and metalloids depend on the underlying atomic structure as well as types and strength of bonding present.  Boiling point is an indicator of the strength of the attractive forces between the atoms.  Substances that have a lower bioling point have weaker attractive forces between their atoms, while higher boiling points indicate stronger attractive forces.  Conductivity is a result of bonds, such as metallic bonds, that are associated with delocalized electrons.  These mobile electrons allow an electrical current to be carried through the substance.  High degrees of ductility are also associated with such bonds.  This is because delocalized electrons allow the atoms to move over one another freely without experiencing high degrees of repulsive forces from other electrons were the electrons to be associated with their respective atoms.  This repulsion causes other, non-ductile solid substances to shatter in response to the same magnitude and direction of the forces acting on the substance.  Properties such as color and luster are a result of the selective absorption of light by the atomic structure. 

 

Physical properties are an aspect of the criterion used to classify substances as metals, nonmetals or metalloids.  Metals usually are ductile, solids at room temperature, have a metallic, shiny luster, and are good conductors of heat and electricity.  Nonmetals tend to be brittle, have a dull luster, and are poor conductors of heat and electricity.   Metalloids have physical properties associated with both metals and nonmetals. 

  

The Grabber:

Photo: Semiconductor wafer, or a thin slice of semi-conductor material, as seen up close.

 

Case Study: 

Semiconductors are used in a multitude of modern applications such as LED (light emitting diode) tail lights in your car, and serve as a foundation from which telephones, televisions and computers are built.  Semiconductors are substances that have properties of both insulators and conductors.  They have conductive properties when an electric field is added (but not as conductive as metals), and act as an insulator when a field is absent.  These properties result from a unique electron configuration within these substances.  Most semiconductors are metalloids (it should be noted that it is inaccurate to use the two terms interchangeably).  Some examples of semiconductors are silicon and carbon (diamond). 

  

Good Questions for Research: 

What properties allow a substance to act as a semiconductor?

This is testable and allows students to see a connection between physical properties and a substance, such as how metalloids display both metallic and nonmetallic behavior and often behave as semiconductors.     

 

Not so good Questions for Research:

What is the atomic number of silicon?

This leads just to a collection of facts.

  

Simulated Research Activities: 

Verbal Design:  How would you test to see if there is a difference in conductive properties of metals and metalloid semiconductors using a voltmeter and strips of metals and metalloid semiconductors?  

 

Testing Metals & Nonmetals - this video illustrates several methods of testing materials including conductivity, luster, and malleability

 

Short Videos you may find useful:

Semiconductors: 3D Animation - an excellent overview of the background information of how semiconductors works, which is great background information for the teacher

 

Diamond Factory - (excellent) 15:00 min Nova Science Now video about artificial diamonds and their use as the semiconductor of the next century. This video helps explain the science behind semiconductors.

 

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