Untitled Essay, Research Paper

Hydrogen bonds are highly strong bonds which join molecules of comparatively little mass. This distinctive feature creates the alone belongingss associated with substances with H bonding, particularly in H20. In most compounds, the mutual opposition of its elements has a negligible consequence on the dipole forces which connect them. However, when H bonds to a little and extremely negatively charged atom, such as N, O, or F, the difference in electronegativity between the atoms causes the shared negatrons to tie in less with the H. Electrons, which usually orbit about both bonded atoms, are more attracted to the karyon of the N, O, or F, than to the proton of the H atom. As a consequence, the H atom basically loses its negatron cloud and assumes the belongingss of a individual proton. This allows it to pick up a brace of unshared negatrons from another nearby atom of N, O, or F. Hydrogen bonding can merely happen with the three mentioned atoms because their electronegativity is great plenty to pull the H negatron. More significantly, the little H atom and little atomic radii of the others allow the unshared negatrons to come really near to the H atom. In larger atoms, as the unshared negatrons attempted to bond with the H, they would be repelled by the negatrons of the atom on the other side of the H. As a consequence of the disassociation of its negatron and ability to bond with two really negatively charged atoms, H bonds are one of the strongest dipole forces, ( though non about every bit strong as covalent bonds ) . Because of the strong bon

ds, the boiling points of hydrogen-bonded substances are much higher than the expected boiling points determined through molar mass trends. More energy is needed to break a hydrogen bond, raising the heat of vaporization. In water, the hydrogen bond contributes to many of its unique properties. The high heat of vaporization causes water to be a in its liquid or solid state under most conditions. Since life on earth started in liquid water, it was essential for water to remain in this state for the majority of the water cycle. Because of this difficulty in breaking bonds connecting H20 molecules, water also has a very high specific heat, 4.184 J/g C . This allows water to not be affected by slight temperature fluctuations, and causes it to moderate the climate, cooling during the hot days, and warming the air during the cold night. It is for this reason that deserts experience such dramatic temperature extremes, and islands maintain a steady year-round climate. Also important, is the effect of hydrogen bonds on ice. When water freezes, the O atoms are bonded to four hydrogens: two covalent bonds and two hydrogen bonds to other H20 molecules. The covalent bonds are shorter than the hydrogen bond, causing the molecules to bond in hexagonal crystals with empty space on the inside. This causes the peculiarity of water in which its frozen state is less dense than its solid state. Such a property makes lakes and rivers freeze from the top down, an important consideration in the evolution of life. When lakes froze, primordial organisms could still dwell on the floor, allowing them to survive through the winters.