Tutor profile: Brian E.
Si tienes una hermana, y ella tiene un hijo, ¿cuál es tu relación con este niño?
El niño sería tu sobrino.
Subject: Basic Chemistry
Why are the Group 18 elements often called "noble gases"?
These elements have completely filled valence shells, meaning that their outermost electrons are in a very stable state. This makes these elements quite unreactive (or 'noble'). Because these atoms have little attraction even towards each other, they tend to be gases under standard conditions.
Subject: Materials Science
All other factors being equal (molecular weight, mer chemical identity, degree of polymerization, etc.), which polymer architecture would you expect to exhibit greater yield strength--linear or branched?
A branched architecture means that there are numerous secondary branches of repeat units extending off of each primary polymer chain. These branches make the molecule sort of 'fuzzy'. This inhibits crystallinity and increases the average distance between molecules since the primary chains can't lie as close to each other. This, in turn, reduces the strength of secondary bonds between the molecules, resulting in lower density and lower strength. A linear architecture, by contrast, has no such appendages--it's just a single primary chain. This makes it much easier for primary chains to arrange themselves in a crystalline fashion. This reduced average distance between molecules produces strong secondary bonds, resulting in higher density and higher strength.
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