【Daily Question】11.9 Multiple-choice question: The reason why oils lose their fluidity at low temperatures is: ( )

The reason why the material loses its fluidity at low temperatures is: (A)

The reason why oils lose their fluidity at low temperatures is: (A. Solidification at low temperatures)

The reason why oils lose their fluidity at low temperatures is: (freezing at low temperatures, structural crystallization)

The reason why oils lose their fluidity at low temperatures is: (A. Solidification at low temperatures, B. Structural crystallization)

The reason why oils lose their fluidity at low temperatures is: (A) A. Solidification at low temperatures B. Structural crystallization C. Chemical changes

【Daily Question】11.9 Multiple-choice question: The reason why oils lose their fluidity at low temperatures is: (ab) A. Solidification at low temperatures B. Structural crystallization C. Chemical changes. Oils gradually lose their fluidity at low temperatures, and there is no fixed solidification temperature. Depending on the composition of the oil, there are two reasons why it loses its fluidity at low temperatures. (1) Viscosity-temperature solidification: For oils with low wax content or those that are wax-free, as the temperature drops, their viscosity increases rapidly. When the viscosity reaches a certain level, the oil turns into an amorphous, viscous glass-like substance and loses its fluidity; this phenomenon is known as viscosity-temperature solidification. The solidification of oils depends primarily on their chemical composition; factors that affect viscosity-temperature solidification include colloidal substances in the oil as well as cyclic hydrocarbons with multiple rings and short side chains. (2) Structural solidification: In oils with a high wax content, as the temperature drops, the solubility of high-melting-point hydrocarbons in the oil decreases; when saturation is reached, these hydrocarbons crystallize and precipitate out. Initially, fine particle crystals that are invisible to the naked eye precipitate, causing the originally transparent oil to become turbid. As cooling continues, the wax crystals gradually grow larger. With further cooling, a large number of wax crystals are formed, and the resulting network-like crystal structure encloses the liquid oil, causing the entire oil to lose its fluidity. This phenomenon is known as structural solidification (or structural freezing). What affects the solidification of the structure are the high-melting-point n-alkanes, isoparaffins, and cyclic hydrocarbons with long alkyl side chains in the oil. Whether it is viscosity-temperature solidification or structural solidification, both refer to the state in which the oil has just lost its fluidity. In reality, at this point the oil has not turned into a true solid; rather, it is in a viscous paste-like state, having merely lost its fluidity under certain conditions.

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Daily Question】11.9 Multiple-choice question: The reason why oils lose their fluidity at low temperatures is: ( ) B A. Solidification at low temperatures B. Structural crystallization C. Chemical changes