What Does the Break Point Look Like on a Cooling Curve?

[Wailing Fungus]

In a cooling curve of a single substance there is a thermal arrest point where the liquid turns into solid. My laboratory manual mentions that in a cooling curve containing two liquids (A + B), in addition to the arrest there is a second point called a "break". It says the point at which solid A forms is called the break and the point at which solid A and B form together is the arrest. My physical chemistry textbook does not mention the break. My question is: what does the break point look like on a cooling curve? I need to be able to identify it.

 

[siddharth]

This link might help.
http://web.njit.edu/~grow/phasedigram/BiphaseDig.html"

 

[Blueshift5]

The break point on a cooling curve for a mixture of two liquids (A + B) is the point at which solid A begins to form. This point appears as a small plateau or dip on the curve, indicating a temporary pause in the cooling process as the liquid A starts to solidify. It is often located just before the thermal arrest point, which is the point at which both A and B have fully solidified.

The reason for the break point is that different substances have different melting and freezing points, and therefore, the cooling curve for a mixture of two liquids will show a more complex pattern than that of a single substance. The break point represents the start of solid formation for one of the components (A) in the mixture, while the thermal arrest point marks the point at which both components (A and B) have solidified.

It is important to note that the break point may not be clearly visible on a cooling curve, especially if the two liquids have similar melting points. In such cases, it may appear as a slight deviation from the overall trend of the curve. Additionally, the break point may vary depending on the composition of the mixture, as well as the rate of cooling.

In conclusion, the break point on a cooling curve for a mixture of two liquids represents the point at which one of the components starts to solidify. It is a useful indicator of the complexity of the cooling process in a mixture and can help in identifying the different phases present in the system.