Final answer:
Fats are solid at room temperature mainly due to their high percentage of saturated fatty acids, while oils are liquid because they contain more unsaturated fatty acids, which prevent tight packing due to the kinks caused by double bonds. a. Fats are simple triacylglycerols and oils are mixed triacylglycerols.
Step-by-step explanation:
The physical state difference between fats and oils lies in their chemical structure, more specifically the types of fatty acids they contain and the presence of double bonds. Fats are usually solid at room temperature because they have a higher proportion of saturated fatty acids, which do not have double bonds and thus have straight chains that can pack closely together, leading to a higher melting point. In contrast, oils are liquid at room temperature because they contain a higher percentage of unsaturated fatty acids, which include one or more double bonds, particularly in the cis configuration, causing kinks in the chains that prevent tight packing and result in lower melting points.
Triglycerides obtained from animal sources are usually solid fats, whereas those from plant sources are generally liquid oils. This distinction comes from the fact that animal fats tend to have more saturated fatty acids, while plant oils have more unsaturated fatty acids. The correct statement that best describes the reason for the difference in physical state between fats and oils is that fats contain a higher percentage of saturated fatty acids than oils do, and therefore have higher melting points than oils, making option 'd' the correct choice for the student's question.