Shapes of Melting Ice

 What shape is submerged ice as it melts?

That depends on temperature apparently ..

 Which suggests that we can infer water temperature in nature by observing the shape of its melting ice.

Scott Weady, Joshua Tong, Alexandra Zidovska, and Leif Ristroph (2022); Anomalous Convective Flows Carve Pinnacles and Scallops in Melting Ice. Phys. Rev. Lett 128(4)  https://doi.org/10.1103/PhysRevLett.128.044502

Diamond Planet Discovered

Scientists from Australia, Germany, Italy, the UK and the USA, have detected a companion planet for Pulsar J1719-1438 in our Milky Way, and they believe that this companion planet could be made of diamond. The planet is thought to be small, less than 60,000km in diameter, with a mass slightly greater than that of Jupiter, about 2 x 10²⁷kg.
P1719-1438 and its planet are so close together that the planet is most likely to be a 'stripped-down' white dwarf, that is, one that has lost its outer layers and over 99.9% of its original mass. Based on the planet's orbiting times, the scientists think that this remnant is likely to be made up mostly of carbon and oxygen, while its high density suggests that the material present is crystalline, which leads them to believe that the planet could contain a sizable proportion of diamond.

Graphite can be transformed into diamond under pressures of more than about 4GPa, as is shown in the simplified phase diagram on the right. On Earth, diamonds can be formed in the mantle where the pressure is great enough to transform carbon sources into diamonds. Diamonds can also form when a meteorite impacts on the Earth because the impact creates a zone of high pressure and temperature in which carbon can be transformed into diamond.

Reference
M. Bailes, S. D. Bates, V. Bhalerao, N. D. R. Bhat, M. Burgay, S. Burke-Spolaor, N. D'Amico, S. Johnston, M. J. Keith, M. Kramer, S. R. Kulkarni, L. Levin, A. G. Lyne, S. Milia, A. Possenti, L. Spitler, B. Stappers, W. van Straten. Transformation of a Star into a Planet in a Millisecond Pulsar Binary. Science, 2011; DOI: 10.1126/science.1208890

Further Reading
Mass Conversions
Density Calculations
Allotropes

Study Questions

1. Convert 60,000km to a distance in:
   • meters
   • centimeters
     
   • millimeters
     
2. Convert 2 x 10²⁷kg to a mass in
   • grams
   • megagrams
   • gigagrams
     
3. What is the approximate radius of of the planet in cm?
4. What is the volume of the planet in cm³ (assuming the planet is spherical)?
5. Calculate the approximate density of the newly discovered planet (in g/cm³).
6. Convert 4GPa to a pressure in:
   • kilopascals
   • pascals
   • megapascals
   • atmospheres
     
   
   
7. Using the phase diagram for carbon in the article above:
   • What is the minimum temperature and pressure required to produce liquid carbon from gaseous carbon?
   • What is the maximum pressure at which graphite can exist?
   • What is the maximum temperature at which graphite can exist?
     
   • How many phases of carbon are present at 4500K and 0.01GPa?
   • What is the triple point for diamond?
     
   
   

Anti-Fog Coating

Fog forms on a surface when water vapor in the air condenses in fine droplets. The fog that forms on glasses is not a continuous film, rather, it consists of tiny droplets of water that coalesce on the surface and reduce light transmission. A good anti-fog coating should prevent the formation of these droplets. Existing anti-fog coatings can't withstand repeated washings so must be re-applied regularly.

Researchers have used polyvinyl alcohol, a hydrophilic compound that allows water to spread uniformly, in the first reported permanent anti-fogging coating.

Four successive layers of molecules, which formed strong bonds with their adjoining layers, were applied to the surface prior to adding the anti-fog compound over this base. The result was a thin, transparent, multilayered coating that does not alter the optical properties of the surface on which it is overlaid. In addition, the chemical bonds that join the different layers ensure the hardness and durability of the entire coating.

Reference:
Pascale Chevallier, Stéphane Turgeon, Christian Sarra-Bournet, Raphaël Turcotte, Gaétan Laroche. Characterization of Multilayer Anti-Fog Coatings. ACS Applied Materials & Interfaces, 2011; : 110307090243075 DOI: 10.1021/am1010964

Further Reading
Physical and Chemical Changes
Balancing Chemical Equations
Intermolecular Forces
Polymers and Polymerization

Study Questions

1. Write a word equation to describe the production of fog.
2. Write a balanced chemical equation to describe the production of fog.
   
3. Is the production of fog an example of a physical or a chemical change? Explain your answer.
4. If vinyl chloride has the formula CH₂=CHCl and vinyl acetate has the formula CH₃COOCH=CH₂, what do you predict the formula for vinyl alcohol to be?
5. Draw a structure for polyvinyl chloride showing three repeating monomer units.
6. Draw a structure for polyvinyl acetate showing three repeating monomer units.
7. Draw a structure for polyvinyl alcohol showing three repeating monomer units.
8. Using your understanding of intermolecular forces, explain how a coating of polyvinyl alcohol could help water droplets forming on glasses.
   

Reaction Mechanism for Ammonium Sulfates's Phase Transition

During a chemical reaction, the atoms in the reactants are rearranged to form new compounds. On a molecular level, the spatial arrangement of electrons and nuclei changes. While the structure of the reactant and product molecules can be measured the reaction mechanism, or the transient structures and molecular motions during a reaction, have remained unknown in most cases, but, this knowledge is a key element needed to understand the reaction.

Scientists at the Max-Born Institute in Berlin have now succeeded in making a "molecular movie" of the thermal phase transitions of ammonium sulfate which is a reversible reaction.

Using an advanced femtosecond laser system which generates a blue pulse of 50 femtosecond duration, they initiated the chemical reaction and then probed the structure of the excited material with high spatial resolution using a synchronised X-ray flash of 100 femtosecond duration. The X-ray pulse is diffracted off a powder made of small crystals, this is known as the Debye-Scherrer method. By simultaneously measuring the many different X-ray reflections they reconstructed the transient distances of atomic lattice planes and in turn the three dimensional distribution of electronic charge within the crystal. The "molecular movie" was created by taking X-ray snap shots at various times after triggering the reaction.

What they found is that the blue flash caused a release of both a proton from the ammonium ion and an electron from the sulfate ion. The proton and the electron then merged to form a hydrogen atom which jumped back and forth between two distant spatial positions.

Reference:
Michael Woerner, Flavio Zamponi, Zunaira Ansari, Jens Dreyer, Benjamin Freyer, Mirabelle Prémont-Schwarz, Thomas Elsaesser. Concerted electron and proton transfer in ionic crystals mapped by femtosecond x-ray powder diffraction. The Journal of Chemical Physics, 2010; 133 (6): 064509 DOI: 10.1063/1.3469779

Study Questions

1. Give the molecular formula for ammonium sulfate.
2. What is the oxidation state (oxidation number) for nitrogen in the ammonium ion?
3. What is the oxidation state (oxidation number) for sulfur in the sulfate ion?
   
4. Write a chemical equation for the overall reaction for the thermal phase transition of ammonium sulfate.
5. What is meant by the term reversible reaction? Explain your answer using the chemical equation above.
6. Draw Lewis structures (electron dot diagrams) for the ammonium ion and the sulfate ion.
7. Draw Lewis structures (electron dot diagrams) for each of the ions above immediately after the laser's blue flash initiates the reaction.
8. Using the new species above, give the oxidation state (oxidation number) for nitrogen and sulfur after the reaction is initiated. Compare these oxidation states to those in questions 2 and 3. Is this an example of a redox reaction? Explain your answer.
9. Define the terms Bronsted-Lowry acid and Bronsted-Lowry base.
10. Are any of the species described in the reaction mechanism for the thermal phase transition of ammonium sulfate acting as Bronsted-Lowry acids or Bronsted-Lowry bases. Explain your answer.
11. Define the terms Lewis acid and Lewis base.
12. Are any of the species described in the reaction mechanism for the thermal phase transition of ammonium sulfate acting as Lewis acids or Lewis bases. Explain your answer.