Recent comments in /f/askscience

MatrixDweller t1_j7el0os wrote

Reply to Why oil fries, while water boils? by SaboKunn

To boil is to heat a liquid to point of vaporization. Like water to 100 °C. Oils boil much higher, like 300-400 °C.

Fry is a cooking term meant to heat something up, possibly with oil to cook it and maybe brown it. You could stir fry with water but I think that's more like sautéing.

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OrbitalPete t1_j7ejhlz wrote

Reply to Why oil fries, while water boils? by SaboKunn

When you put food in oil it's at s much hight temperature than boiling in water. As a result moisture in the food is boiled out which dies the food. Its also hot enough that browning (maillard reactions) and crisping can occur.

The bubbling when you deep fry is the water coming out of the food and vaporising. You can get pills to boil as well, although they aren't pure liquids boiling is generally accompanied by a lot of smoking, burning of components in the oil, and - because oils are generally flammable - the vaporised fraction often ignites.

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ECatPlay t1_j7e842q wrote

Reply to Understanding that deuterium and tritium are simply isotopes of hydrogen, is there an equivalent periodic table that shows all known elements and their isotopes? by [deleted]

Sure, it's called a Chart of the Nuclides or Table of the Nuclides. Instead of being organized with similar chemical properties in a column, it is organized based on the number of protons and number of neutrons, in columns for one and rows for the other. There are a couple of orientations used. Wikipedia has a Full Table that starts with hydrogen in the upper left, and is oriented using columns for each element (with increasing atomic number going to the right), and rows for each number of neutrons (for the different isotopes of each element) going down.

A full table like this is fine on a wall chart, but it's easier to navigate online. Entering the atomic symbol and isotope mass number in this Chart of the Nuclides, for instance. Entering "Cl" and "35" for chlorine, for example, takes you right to ^(35)Cl. This table uses the other common orientation: with hydrogen in the lower left, increasing atomic number in each row going up, and increasing number of neutrons in each column going to the right. More like a standard X and Y plot.

This layout is convenient for nuclear physicists, in that (among other things) it's easy to relate the starting atom to the result of a nuclear process. Beta decay (loss of an electron), for instance, would transform one of the neutrons in an atom into a proton, increasing the atomic number but not the mass. This corresponds to just moving diagonally up one row and to the left one column in the Chart of the Nuclides: up to ^(35)Ar from ^(35)Cl in our chlorine example. (Not that this is a highly probable event, in the case of ^(35)Cl). And radioactive decay with neutron emission takes you one column to the left in the same row: ^(34)Cl from ^(35)Cl. And Alpha radiation (emission of a helium nucleus, 2 neutrons and 2 protons) is just moving diagonally down 2 rows and left 2 columns: ^(31)P from ^(35)Cl.

But you asked this as a Chemistry question, and although it's periodicity is not related to chemical behavior, it does bring out the role of isotopes in chemistry. For instance, we're used to thinking of the molecular weight of an element as the sum of protons and neutrons. But the molecular weight given for chlorine in the Periodic Table of the Elements, 35.453, is not an integer. So at first this may seem odd. But the chlorine row in the Chart of the Nuclides brings out the fact that elemental chlorine is a mixture of isotopes, mostly ^(35)Cl and ^(37)Cl, with a natural abundance of 76% for ^(35)Cl and 24% for ^(37)Cl. And this averages out to the molecular weight of 35.453 in naturally occurring chlorine.

Another chemical consideration where understanding the isotopes helps, is in interpreting Mass Spectra. When chlorine is present in a chemical being sampled for instance, since 76% of the time the chlorine atom will be ^(35)Cl and 24% of the time it will be ^(37)Cl, this will show up as very characteristic pairs of peaks in a 3:1 ratio, 2 mass units apart in all chlorine containing fragments in the Mass Spectrum. This is a big help in the interpretation of fragmentation patterns.

(Edit: got my directions crossed)

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rootofallworlds t1_j7e2j3t wrote

Reply to Is there a term for lake bottoms that "hour glass" (temporarily becomes wider following a "shelf" as the depth increases ) , how do bathymetric maps depict this, and does this have a common affect on turbidity, thermoclines, or other characters? by Irisgrower2

I don’t know any specific term. A lake like you describe is a rare thing. They might occur in karst terrain, but the size of any such lakes are fairly small. The largest cenotes (flooded sinkholes) are a few hundred metres across and won’t necessarily have a below the waterline undercut.

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