User:H Padleckas/sandbox

Halochromism in chromophores
Halochromism occurs when a substance changes color as the pH changes. This is a property of pH indicators, whose molecular structure changes upon certain changes in the surrounding pH. This change in structure affects a chromophore in the pH indicator molecule. For example, phenolphthalein is a pH indicator whose structure changes as pH changes as shown in the following table:

In a pH range of about 0-8, the molecule has three aromatic rings all bonded to a tetrahedral sp3 hybridized carbon atom in the middle which does not make the &pi;-bonding in the aromatic rings conjugate. Because of their limited extent, the aromatic rings only absorb light in the ultraviolet region, and so the compound appears colorless in the 0-8 pH range. However as the pH increases beyond 8.2, that central carbon becomes part of a double bond becoming sp2 hybridized and leaving a p orbital to overlap with the &pi;-bonding in the rings. This makes the three rings conjugate together to form an extended chromophore absorbing longer wavelength visible light to show a fuchsia color. At pH ranges outside 0-12, other molecular structure changes result in other color changes; see Phenolphthalein for details.

Variables
In the diagram at right with white to move next, black is threatening with the following rook sacrifice leading to mate.
 * 40. ........ Rh1+
 * 41. Kxh1 Qh2#

The pawn on g2 cannot take the rook on h3 because the queen on g3 is pinning it with a vertical line of attack. The only move to prevent the above moves is 40. Nf4 which temporarily blocks black's bishop from protecting his queen, but to no avail. The black bishop can take the knight by 40. ..... Bxf4 renewing the same threat of mate in 2 or Black can respond as follows to mate anyway:
 * 40. Nf4  Qh2+
 * 41. Kf 2 R/h3xf 3#

In this case, white could not take the mating rook now on f 3 with the g2 pawn because the queen on h2 would now be pinning it with a horizontal line of attack.

For =Tabular iceberg= article

Antarctic icebergs formed by breaking off from an ice shelf, such as the Ross Ice Shelf or Ronne Ice Shelf, are typically tabular. The largest icebergs in the world are formed this way.

Chess sacrifice
Example: In the diagram at right with white to move next, what sacrifice move should white make ?

Answer: Force a bishop sacrifice by moving the white bishop on f 5 to g6 with check. The only way for black to get out of check is to take the checking bishop with black's pawn on h7. White follows with queen retakes pawn on g6 producing checkmate.


 * White can force mate in 2 in the diagram at right as follows.
 * 1. Bg6+  h7xg6
 * 2. Qxg6 #

Energy level
for Gas leak article

For example, a natural gas leak caused an explosion destroying a school in New London, Texas in 1937, killing about 300 (or more) students and teachers.

Theory of Ultraviolet-Visible (UV-Vis) Spectroscopy



∞I∞

R∞

Check (chess)
Example: In this example position, white's pawn on c5 is in position to capture black's queen except that it is pinned along its 5th rank, blocking black's rook on e5 from capturing white's queen; an immediate capture by the c5 pawn would result in an even exchange of queens. However, white's queen can move out of that rank by checking with Qa6+, forcing black to get out of check on the following move and simultaneously unpinning white's c5 pawn, allowing it to capture the black queen on white's next move by cxd6.

Blind swine mate
The name of this pattern is attributed to Polish master Dawid Janowski referring to coupled rooks on a player's 7th rank as swine. In the first partial position at right and assuming there are no interferences, white can force checkmate as follows: For this type of mate, the rooks on white's 7th rank can start out on any two of the files from a to e, and although black pawns are commonly present as shown, they are not really necessary to effect the mate. The rightmost diagram shows the corresponding partial position after white checkmates according to the preceding moves listed.
 * 1) Rxg7+  Kh8
 * 2) Rxh7+  Kg8
 * 3) Rbxg7#