3: Descriptive

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Name: ______________________________

Section: _____________________________

Student ID#:__________________________

PASSPORT:

The study of chemical elements, the compounds they form, their uses and the energy

changes that accompany their chemical reactions is called descriptive chemistry. Chemists tend to think about chemistry in three different ways:

Symbolic—this includes writing chemical formulas, including proper use of subscripts and superscripts, as well as other accompanying information that helps us understand them; for example (s), (aq), (g), etc.
Macroscopic-What does the compound/element look like (a shiny solid, a colorless gas, etc); how do we tell if it is reacting with something else (Is a color change observed? A ball of flame?) and what is it used for?
Nanoscale-How are the individual particles arranged, and how are they interacting with their neighbors? (If we could “see” individual atoms or molecules, what sort of chemical bonds or intermolecular forces hold them to their nearest neighbors? Is the arrangement regular or random? Are the particles touching or is there a lot of empty space?

In YouTube, search for a video on reaction of sodium and chlorine and watch it.
Complete the following chart for this reaction.
- Some table entries are already completed as examples. Be as complete and accurate as possible.
  
  sodium + chlorine -> product(s)
Now locate macroscopic descriptions for the elemental forms of the other halogens.
Videos for the reaction of the other halogens with sodium are harder to find. Which would be the most and least reactive? Explain your answer.
Make a prediction of the sign of the entropy change that accompanies the reaction of sodium and chlorine. Explain your choice.
Make a prediction for the sign of the enthalpy change for the reaction of sodium and chlorine. Explain your choice.
Based on the video, what is the sign of the free energy change for the reaction in the video?
Now watch videos that show the reactions of sodium and potassium with water.

sodium + water -> product(s)
How does the intensity of the reaction differ when sodium is replaced with potassium? Provide a reason.
As you go from the top of the family to the bottom, the alkali metals and the halogens show opposite trends in reactivity. Explain why.

Calcium is in the same row of the periodic table as potassium.

Now view the video of calcium and water.
How does the vigor of reaction compare to potassium? Explain the reason behind this horizontal trend.

The University of Nottingham has created a “periodic table of videos” of the elements. Go to the site (http://www.periodicvideos.com/) and pick an element that you haven’t seen in a video yet. Also do not pick He, Ne or Ar.

Complete the symbolic/nanoscopic/macroscopic table for one of its reactions.
Give two uses of the element or unusual properties of the element mentioned in the video.