Week 7 - Molecular Weight

1. Inert Gas of the Week
2. Avogadro's Hypothesis
3. What is a Mole?
4. How is Chikyu doing?

1.
Inert gases - the most stable of the elements on the periodic table, i.e. they are not reactive in normal conditions;
I choose to look at Helium, specifically in liquefied form of isotope He-4

• Helium is a Noble Gas with 2 protons, 2 neutrons, and 2 electrons - 4.002602(2) g·mol
• Helium-4 is the most naturally occurring isotope of Helium -"making up about 99.99986% of the helium on earth"
• With regard to the liquefied state of Helium, I find this particularly fascinating - "When helium-4 is cooled to below 2.17 kelvins (–271 °C), it becomes a superfluid, with properties that are very unlike those of an ordinary liquid. For example, if helium-4 is kept in an open vessel, a thin film will climb up the sides of the vessel and overflow. Another name for this property of Helium is Rollin film. This strange behaviour is a result of the Clausius-Clapeyron relation and cannot be explained by the current model of classical mechanics nor by nuclear or electrical models; it is only understood as a quantum mechanical phenomenon." (wikipedia)
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• Due to Helium's naturally stable state and resistance to bond, especially with itself, it resists forming into a liquid and requires extremely low temperatures to achieve liquid states. It will remain a liquid even at absolute zero temperatures (without added pressure)!
• With added pressures and absolute zero temperatures, helium can achieve crystalline formation with only slight distinguishing qualities from liquid forms.
• More on Helium's amazing liquid and superfluid properties -

• Helium II is a superfluid, a quantum-mechanical state of matter with strange properties. For example, when it flows through even capillaries of 10⁻⁷ to 10⁻⁸ m width it has no measurable viscosity. However, when measurements were done between two moving discs, a viscosity comparable to that of gaseous helium was observed. Current theory explains this using the two-fluid model for helium II. In this model, liquid helium below the lambda point is viewed as containing a proportion of helium atoms in a ground state, which are superfluid and flow with exactly zero viscosity, and a proportion of helium atoms in an excited state, which behave more like an ordinary fluid.^[7]

  Helium II also exhibits a creeping effect. When a surface extends past the level of helium II, the helium II moves along the surface, seemingly against the force of gravity. Helium II will escape from a vessel that is not sealed by creeping along the sides until it reaches a warmer region where it evaporates. It moves in a 30 nm-thick film regardless of surface material. This film is called a Rollin film and is named after the man who first characterized this trait, Bernard V. Rollin.^[8][9] As a result of this creeping behavior and helium II's ability to leak rapidly through tiny openings, it is very difficult to confine liquid helium. Unless the container is carefully constructed, the helium II will creep along the surfaces and through valves until it reaches somewhere warmer, where it will evaporate. Waves propagating across a Rollin film are governed by the same equation as gravity waves in shallow water, but rather than gravity, the restoring force is the Van der Waals force.^[10] These waves are known as third sound.

• Mercury is used for all sorts of things... of course for balloons and blimps but also for deep-sea diving oxygen mixtures, rocketry, arc-welding, as a tracer-gas, and in liquid states as a superconductor.

2.
Avogadro's famous hypothesis - that equal volumes of gases, at the same temperature and pressure, contain equal numbers of molecules.

1. Correct - Hypotheses do not become Laws
2. Correct - Cl2O is the correct formula for Chlorine 50 mL Oxygen 25 mL
3. Initially incorrect, I misstated that equal volumes of gases contain equal numbers of particles when it is in fact equal numbers of molecules. I then selected the correct answer - the formula for ammonia as Dalton would have it would have been NH.

Avogadro's number - N_A the number 6.02 x 10²³ (or more accurately 6.022 1415 x 10²³ with an uncertainty of 0.000 0010 x 10²³)

3.
What exactly is a mole? A mole is a unit of measurement that equals the chemical amount of a substance. It is a quantity of something that equals the molecular mass of a certain element. (1)

4.
Chikyu - the ship that was drilling to the deepest parts of the Earth; how is it doing??


In an article about the ship and its technology on Ship Technology.com, I found mention of it not having really begun drilling until 2007;

"The Chikyu was delivered to its owners in 2005, but since then it has been carrying out a range of system integration tests. These were followed by a shakedown cruise, undertaking test drilling off the Shimokita Peninsula to ensure that everything is working satisfactorily before it commences full operations in 2007. It is anticipated that future operations will be carried out off Kenya as well as off Australia."

And Science Daily.com has some more news from early 2007:

"Their achievement marks the launch phase of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), a major research initiative into the triggers and mechanisms of earthquakes and tsunamis supported by the Integrated Ocean Drilling Program (IODP). NanTroSEIZE is expected to continue until 2012, with the ultimate objectives of drilling across the plate boundary fault responsible for magnitude 8 earthquakes to sample the rocks and fluids in the fault, and to place instruments within it to monitor activity and conditions leading up to the next great earthquake."

It appears as though Chikyu has only just begun to explore the Earth's crust.