Lab 8.1 Percent Composition [Due Friday 3/4]

According to the Topps Company Inc, Bazooka Bubble Gum contains 3g of sugar per piece. In your experiment you calculated the percent sugar of the gum, and also did a percent error calculation to compare how much you actually got out.

Propose and explain at least one source of error in this experiment. Make sure you explain how it affected your results.

Explanations that are not acceptable include error in calculations, and errors in measurement. If you made these errors you would simply redo the calculation or the measurement.

Explanations that are acceptable would include reasons why the amount of sugar that you said disappeared was different than the amount of sugar represented on the box. When you do this you need to be sure that explain whether this error would make your value for the amount of sugar higher or lower, and how this influenced your results.





Enrichment

This blog is pretty straight forward and easy. I am looking for some feedback about the blog process. What makes them good and what makes them bad. Do you feel like you have enough help when you need it? Do the questions make you think, are they too easy, too confusing? Please tell me why you think what you do. I am looking for feedback that I can use for my graduate class. It does not need to be positive, but if you have negative things to say please try to make them constructive (I want to make the blog process better).

Lab 7.4: Reactivity of Metals

1.  Answer the lab question on the first page of this lab.  CITE EVIDENCE FROM YOUR OBSERVATIONS! Make sure you explain thoroughly.

2.   Why do elements in the same column on the Periodic Table tend to have VERY SIMILAR properties?  Explain in terms of electron configuration! Use specific examples from your groupings.

3.   Describe what happens when an atom of sodium atom interacts with an atom of a nonmetal.  In your description, indicate:

a.   Whether the sodium atom loses or gains electrons,

b.   Whether the sodium atom becomes a positive or negative ion,

c.   The electrical charge of the sodium ion,

d.   Which noble gas sodium’s electron configuration becomes like,

e.   Whether the sodium atom becomes more or less stable as a result of reacting.

ENRICHMENT: 

The elements Li, Na and K are too reactive to be found in nature as pure elements.  Research how chemists obtain pure sodium in the form like we used in lab.

Lab 7.3 Periodic Trends Activity

These three trends are more challenging to explain, explain them:

·        Atomic radii trend going from left to right across a period.  The heaviest elements in a period have the smallest radii. WHY?

              ·        Electronegativity decreases when you move down a group. The larger the atom in the same group, the less it attracts electrons. WHY?

·        Ionization energies as you go from left to right across a period.  It kind of makes sense that it is harder to strip an electron from a non-metal than from a metal, but WHY is this so?

The key to explaining these trends is to figure out what “nuclear charge” is, and then to figure out what it has to do with these property trends.  Google will be a big help if you ask the right question in the search bar!  Good luck, and of course, talk with your teacher as needed!



Why do you think the trends are referred to as being "PERIODIC." Hint the word periodical is sometimes used with magazines and newspapers that are delivered at regular intervals.

Lab 7.2 Atomic Mass of Pennium

In this lab we used pennies as a model for atoms of the element that were isotopes. Explain why pennies are a good model for isotopes, you might want to include what is similar about the pennies and what differs.

Were there any problems using pennies as a model for isotopes? If so what was it?

The atomic mass of chlorine is 35.45 and there are two naturally occurring isotopes of chlorine: Cl-35 and Cl-37. 

1)  Explain why the atomic mass of Cl is 35.45 amu’s, in terms of relative abundance of the two isotopes of Cl.

2)  Explain the difference between Cl-35 and Cl-37, make sure to mention what is the same in each atom, and also what is different in each atom.

3) The terms mass number and atomic mass are sometimes incorrectly used interchangeably (I do it also), what is the difference between the two terms. If you need a hint to get started, use the masses above from chlorine (35.45 amu vs 35 amu and 37 amu).

ENRICHMENT: 

1.  Research how a mass spectrometer is used to determine the relative abundances of the different isotopes of an element.  A drawing or schematic is encouraged.

2.  Find out how atoms of Uranium – 235 are removed from a natural sample of uranium in order to make “enriched” uranium for use in nuclear power plants and/or nuclear weapons.


3.  The Iranians are currently trying to enrich uranium using the high speed centrifuge method. If you are really interested in reading some interesting computer espionage information go to news.google.com and search STUXNET. It is a computer virus that was written to disrupt the nuclear fuel enrichment, to prevent weapons grade uranium from being made.

Lab 7.1 Flame Test and Emission Spectra

Conclusion:

1.  After seeing the spectra of various elements in this lab, why do you think an element’s spectrum is often called its “fingerprint?”   Explain using the terms ground state, excited state, and electron configuration.

2. Explain how a spectra is formed. Make sure to include the process and the steps that occur. This is important that you can describe what happens during the changes between ground and excited state, and how energy is released and absorbed.

ENRICHMENT:

1.  Research the discovery of the element Helium, and why it is given the name it has.

2.  Find out how astronomers use what is called a “red shift” or a “blue shift” to know whether a galaxy is moving towards or away from our galaxy.  To do this:

a)  Explain what blue shifts and red shifts are, and what they have to do with an element’s spectrum.

b)  Explain how the ratio of blue shift to red shift galaxies is used as evidence that the universe is expanding.

c)  Find out what Sir Edwin Hubble had to do with all this.