Why should melting points always be reported as a range rather than as a single temperature?

The melting point is a physical property of a solid and can be used to help identify a substance. In practice, a solid usually melts over a range of temperatures rather than at one specific temperature. For this reason it is more useful to speak of a melting point range.

What affects the melting point of a compound?

The force of attraction between the molecules affects the melting point of a compound. Stronger intermolecular interactions result in higher melting points. In organic compounds the presence of polarity, or especially hydrogen bonding, generally leads to higher melting point.

Why do some compounds not melt?

The biggest chemical explanation of why some substances don’t melt is that many decompose instead. This is true for many complex organics like paper. IF you add enough energy to (theoretically) melt them you have already added enough to shake the component molecules apart.

How could the rate of heating influence the melting point?

At high heating rates (> 10 K/min), the sample temperature increases so rapidly to higher temperatures that the melting process is completed before the reaction has really begun.

Why is the melting point of a substance actually a melting range and therefore should never be recorded as a single temperature?

Because the actual melting point of a substance is measured starting from the temperature at which the first tiny droplet of liquid can be detected to the temperature where all the solid sample are converted to liquid form, which gives a range. So technically a melting “point” does not exist.

Why should melting points be quoted as ranges rather than exact numbers even for pure compounds?

LAB C: Why is a melting range recorded for a pure sample instead of a melting point? A pure compound will melt over a narrow range and an impure compound will melt over a broad range. As heat is applied to the apparatus of a pure sample, a high energy input is needed to break strong IMFs.

What affects the melting and boiling points of a substance?

The amount of energy needed to change state from solid to liquid, and from liquid to gas, depends on the strength of the forces between the particles of a substance. Every substance has its own melting point and boiling point . The stronger the forces between particles, the higher its melting and boiling points.

When a compound contains an impurity its melting point will be?

A substance (solid) containing soluble impurities usually melts at a lower temperature than the pure compound. It can also melt over a wide range of temperatures and is called the “melting point depression.” In general, the smaller the range of melting temperatures, the higher the purity of the sample.

What is the melting point melts completely and smoothly or a portion does not melt of water?

The melting point of ice is 0°C. The melting point of a solid is the same as the freezing point of the liquid. At that temperature, the solid and liquid states of the substance are in equilibrium. For water, this equilibrium occurs at 0°C….Melting Point.

What happens when the heating rate is too great?

If the heating rate was too high, the measured value would exceed the hemispherical temperature, resulting in an elevated melting point.

Why in terms of accuracy and precision is the heating rate important for a melting point determination?

Heating slowly and steadily allows for accuracy and precision in recording the temperature at which the sample completely melts. Heating too fast gives inaccurate data misleading the experiment. Melting points are used to identify unknown compounds and substances.