Search results
Results From The WOW.Com Content Network
While chemically pure materials have a single melting point, chemical mixtures often partially melt at the temperature known as the solidus (T S or T sol), and fully melt at the higher liquidus temperature (T L or T liq). The solidus is always less than or equal to the liquidus, but they need not coincide.
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa.
However, in group XIII (boron family), the electronegativity first decreases from boron to aluminium and then increases down the group. It is due to the fact that the atomic size increases as we move down the group, but at the same time the effective nuclear charge increases due to poor shielding of the inner d and f electrons.
At the melting point, the ordering of ions or molecules in the solid breaks down to a less ordered state, and the solid melts to become a liquid. Substances in the molten state generally have reduced viscosity as the temperature increases. An exception to this principle is elemental sulfur, whose viscosity increases in the range of 130 °C to ...
The melting point of a substance is the point where it changes state from ... decreases down the group: lithium reacts completely at 700 °C, but sodium at 900 °C ...
A comparison of S N 1 to S N 2 reactions is to the right. On the left is an S N 1 reaction coordinate diagram. Note the decrease in ΔG ‡ activation for the polar-solvent reaction conditions. This arises from the fact that polar solvents stabilize the formation of the carbocation intermediate to a greater extent than the non-polar-solvent ...
Ionic compounds generally have a high melting point, depending on the charge of the ions they consist of. The higher the charges the stronger the cohesive forces and the higher the melting point. They also tend to be soluble in water; the stronger the cohesive forces, the lower the solubility. [3]
At the temperature of the melting point, 0 °C, the chemical potentials in water and ice are the same; the ice cube neither grows nor shrinks, and the system is in equilibrium. A third example is illustrated by the chemical reaction of dissociation of a weak acid HA (such as acetic acid, A = CH 3 COO −): HA ⇌ H + + A −. Vinegar contains ...