Triple point

Examples of Triple point in the following topics:

• Solid to Gas Phase Transition

  • But at temperatures below that of the triple point, a decrease in pressure will result in a phase transition directly from the solid to the gaseous.
  • Also, at pressures below the triple point pressure, an increase in temperature will result in a solid being converted to gas without passing through the liquid region.
  • This is because the pressure of their triple point is very high and it is difficult to obtain them as liquids.
  • Notice the triple point of the substance.
  • At temperatures and pressures below those of the triple point, a phase change between the solid and gas phases can take place.

• Major Features of a Phase Diagram

  • The major features of a phase diagram are phase boundaries and the triple point.
  • The triple point is the point on the phase diagram where the lines of equilibrium intersect -- the point at which all three distinct phases of matter (solid, liquid, gas) coexist.
  • At the triple point, water in the solid, liquid, and gaseous states coexist.
  • The green line marks the freezing point (or transition from liquid to solid), the blue line marks the boiling point (or transition from liquid to gas), and the red line shows the conditions under which a solid can be converted directly to a gas (and vice-versa).

• Aluminosilicates

  • The triple point of these three polymorphs is located at a temperature of 500 °C and a pressure of 0.4 GPa.

• Interpreting Phase Diagrams

  • By examining the phase boundaries and the triple point, researchers can use phase diagrams to understand under which conditions a pure sample of matter exists in two or three state equilibrium.
  • Phase diagrams can also be used to explain the behavior of a pure sample of matter at the critical point.
  • The critical point, which occurs at critical pressure (Pcr) and critical temperature (Tcr), is a feature that indicates the point in thermodynamic parameter space at which the liquid and gaseous states of the substance being evaluated are indistinguishable.
  • At this point and beyond it, the substance being evaluated exists as a "supercritical fluid".
  • A typical phase diagram illustrating the major components of a phase diagram as well as the critical point.

• Freezing Point Depression

  • Freezing point depression is the phenomena that describes why adding a solute to a solvent results in the lowering of the freezing point of the solvent.
  • In this equation, $\Delta T_f$ is the freezing point depression, Kf is the freezing point depression constant, and i is the van 't Hoff factor.
  • The value of 0.93 oC is the change in the freezing point.
  • A triple phase diagram which shows the pressure and temperature of the normal boiling and freezing points of a solvent (green lines) and the boiling and freezing points of a solution (purple lines).
  • Discuss the effects of a solute on the freezing point of a solvent

• Double and Triple Covalent Bonds

  • Hybridization describes the bonding situation from a specific atom's point of view.
  • The simplest triple-bonded organic compound is acetylene, C2H2.
  • Similar to double bonds, no rotation around the triple bond axis is possible.
  • In this case, four orbitals are produced which point along the direction of the vertices of a tetrahedron.
  • Describe the types of orbital overlap that occur in single, double, and triple bonds

• Catalytic Hydrogenation

  • A carbon-carbon triple bond may be located at any unbranched site within a carbon chain or at the end of a chain, in which case it is called terminal.
  • Since the most common chemical transformation of a carbon-carbon double bond is an addition reaction, we might expect the same to be true for carbon-carbon triple bonds.
  • Similarly, a triple bond is stronger than a double bond, but not 50% stronger.
  • However, careful hydrogenation of an alkyne proceeds exclusively to the alkene until the former is consumed, at which point the product alkene is very rapidly hydrogenated to an alkane.
  • Consequently, reduction of triple bonds occurs selectively at a moderate rate, followed by rapid addition of hydrogen to the alkene product.

• Covalent Bonds

  • Triple bonds occur when six electrons are shared between the two atoms and consist of one sigma bond and two pi bonds (see later concept for more info about pi and sigma bonds).
  • Ionic solids are generally characterized by high melting and boiling points along with brittle, crystalline structures.
  • Covalent compounds, on the other hand, have lower melting and boiling points.

• Naming Alkenes and Alkynes

  • Alkenes and alkynes are named similarly to alkanes, based on the longest chain that contains the double or triple bond.
  • Alkenes are hydrocarbons that contain one or more double bonds, while alkynes contain one or more triple bonds.
  • Alkene and alkyne compounds are named by identifying the longest carbon chain that contains both carbons of the double or triple bond.
  • The carbon backbone is numbered from the end that yields the lowest positioning for the double or triple bond.
  • For multiple double or triple bonds, "di-," "tri-," or "tetra-" can be added prior to the "-ene" or "-yne."

• Physical Properties of Covalent Molecules

  • Covalent compounds generally have low boiling and melting points, and are found in all three physical states at room temperature.
  • According to the theory, triple bonds are stronger than double bonds, and double bonds are stronger than single bonds.
  • Discuss the qualitative predictions of covalent bond theory on the boiling and melting points, bond length and strength, and conductivity of molecules