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Target hardening, also referred to simply as hardening when made clear by the context, is a term used by police officers, those working in security, and the military referring to the strengthening of the security of a building or installation in order to protect it in the event of attack or reduce the risk of theft.
The effect originates from the disruption of highly dynamic hydrogen bonds between molecules of liquid water. Polar chemical groups, such as OH group in methanol do not cause the hydrophobic effect. However, a pure hydrocarbon molecule, for example hexane, cannot accept or donate hydrogen bonds to water. Introduction of hexane into water causes ...
Hydroxyl groups (-OH), found in alcohols, are polar and therefore hydrophilic (water liking) but their carbon chain portion is non-polar which make them hydrophobic. The molecule increasingly becomes overall more nonpolar and therefore less soluble in the polar water as the carbon chain becomes longer. [5]
The hydrophobic interaction is mostly an entropic effect originating from the disruption of the highly dynamic hydrogen bonds between molecules of liquid water by the nonpolar solute, causing the water to form a clathrate-like structure around the non-polar molecules.
The hydrophobic effect was found to be entropy-driven at room temperature because of the reduced mobility of water molecules in the solvation shell of the non-polar solute; however, the enthalpic component of transfer energy was found to be favorable, meaning it strengthened water-water hydrogen bonds in the solvation shell due to the reduced ...
Surfactants are composed of a polar head group that is hydrophilic and a nonpolar tail group that is hydrophobic. The head groups can be anionic, cationic, zwitterionic, or nonionic. The tail group can be a hydrocarbon, fluorocarbon, or a siloxane. Extensive variation in the surfactant’s solution and interfacial properties is allowed through ...
The study also supports the fact that ethanol prefers to bond just below the hydrophilic region of the phospholipids near the phosphate groups. The location of the ethanol creates a strong hydrogen bond between the water molecules. [3] The results are depicted in the simulations and supported by mass density profiles as well.
Nonpolar bonds generally occur when the difference in electronegativity between the two atoms is less than 0.5; Polar bonds generally occur when the difference in electronegativity between the two atoms is roughly between 0.5 and 2.0; Ionic bonds generally occur when the difference in electronegativity between the two atoms is greater than 2.0