23Apr 2019 by Vincent Summers No Comments

Diatomic Molecules: Degrees of Freedom and Equipartition of Energy

Chemistry, Physics
[caption id="attachment_24378" align="alignright" width="480"] A useful, but rough working model[/caption] Diatomic molecules have three translational degrees of freedom – but they have rotational and vibrational varieties as well. How do all these degrees of freedom relate to the distribution of molecular energy? To Begin With The location of any particle lies within three-dimensional space. The direction in which a particle moves is described by the three variables, usually written X, Y, and Z. As Ken Koehler of the University of Cincinnati informs us, atoms may be viewed as single points without size – so there are only three translational degrees of freedom for a given atom. Degree of Freedom of Diatomic Molecules Although it’s tempting to assume only three degrees of freedom exist for all “particles,” such is not the…
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18Apr 2019 by Vincent Summers 1 Comment

Introduction to Chemistry Subscripts and Superscripts

Chemistry, Education
Subscript and superscript can make all the difference when it comes to chemical formulas. Molecules, compounds, and other chemical structures include more than one atom. Sometimes, there are multiples of one particular atom. For instance, anhydrous aluminum chloride features one atom of aluminum joined to or combined with three atoms of chlorine. Its chemical formula reflects this: AlCl3. But – simply knowing how to use a number in this instance is not enough. It is essential to know the proper use of subscripts and superscripts. Subscripts in Chemistry Notice the number 3 is written as a subscript, or a number that is smaller than the other text, and below the normal text line, in the formula for anhydrous aluminum chloride above. The concept of a multiplicity of atoms is conveyed…
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19Jun 2017 by Vincent Summers No Comments

Do Lone Atoms or Molecules Assume States of Matter?

Physics
Search the Internet for the definition of states of matter and much comes up. Perhaps you are the sort of reader who peeks first at Wikipedia to get some ideas what other sites you will visit to obtain answers to your questions. At any rate, you will note basic descriptions for the states of matter you experience every day. Take the following discussion for what it is: a hypothetical discussion on the nature of matter. If you can demonstrate its veracity or illegitimacy, please do that in the Comments section, below. States of Matter Solid: “Atoms or molecules fixed in location and locked in place.” How are these particles locked into place? They bond to each other and do not readily move around, much like the assembled pieces in a…
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19Apr 2017 by Vincent Summers 2 Comments

What Makes Ice Slippery Compared to Other Solids? A Combination of Factors?

Chemistry, Physics
[caption id="attachment_17673" align="alignleft" width="380"] Image: Tvb hof - Own work, CC BY-SA 3.0[/caption] “Be careful if you will be driving this evening,” the weather forecaster declares. “The road will be a sheet of ice.” Whether tar and gravel, asphalt, or concrete, roads most of the year are not slippery. Yet come winter, those roads can be dangerously slippery. What makes ice and icy roads so slippery? What Makes Ice Slippery One line of thinking is that ice is slippery because water (H₂O) expands as it freezes. When a heavy object rests upon a sheet of ice, the pressure imparts energy to the molecules immediately beneath the weight, pressing them down, melting it. The water acts much like a lubricant, making the ice slippery. In truth, if the ice is reasonably…
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27Nov 2014 by Vincent Summers No Comments

LCAO MO Chemical Bonding Theory and Examples

Chemistry
[caption id="attachment_8903" align="alignright" width="440"] Antibonding sigma orbital.[/caption] LCAO MO The nature of the chemical bond has been of interest for hundreds of years. Theories have been developed to explain how atoms combine to form molecules. The most successful theory to date is the (L)inear (C)ombination of (A)tomic (O)rbitals - (M)olecular (O)rbitals or LCAO MO bonding theory. You've got it: yet another acronym. Atoms have nuclei. These contain protons and neutrons. Electrons travel around these nuclei. Orbitals are mathematical functions that describe their trajectories. As atoms form molecules, atomic orbitals combine to form molecular orbitals. Since orbital functions are described by the Schrödinger wave equation and that equation is linear, molecular orbitals can be described by the linear additive combining of atomic orbitals. Example of Hydrogen Ordinary hydrogen has one proton,…
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