Without an extensive Bio-Chem explanation, Fatty Acids are carboxylic acids with long hydrocarbon chain tails. Fatty Acids are grouped together depending on whether they are Saturated Fats (with shorter molecular tails) or Unsaturated Fats (with longer molecular tails). Saturated Fatty Acids and Unsaturated Fatty Acids, have different Melting points, the temperatures where they become liquid.

Because of their short tails, Saturated Fatty Acids can pack their molecules in more densely and remain solid at higher temperatures. Unsaturated Fatty Acids need room for their longer tails and cannot pack molecules in as tightly. They tend to melt at lower temperature and can be liquids at room temperature. Oils are Fats that are liquid at room temperature 77° F (25°C).

The most common Fatty Acids are listed below in their respective categories.

 [Note that there are both a Linoleic Acid (Lin-Oleic) and a Linolenic Acid (Lin-Olenic)].

SATURATED FATTY ACIDS

Lauric Acid         Lauric Acid melts at 111° F (44° C)

Palmitic Acid      Palmitic Acid melts at 145° F (63° C)

Myristic Acid       Myristic Acid melts at  130° F (54° C)

Stearic  Acid       Stearic Acid melts at 158° F (70° C)           

UNSATURATED FATTY ACIDS

Oleic   Acid                          melts at 60° F (16° C) 

 Linoleic Acid                      melts at  23° F (-5° C)

Linolenic  Acid                   melts at 12° F (-11° C)

Arachidonic  Acid              melts at  - 58° F (-50° C)

The mixture of how the single bonded, Saturated Fatty Acids and double bonded Unsaturated Fatty Acids combine determines what type of Fat will be created. If a single unsaturated, double-bonded, Fatty Acid is present amongst the 3 Fatty Acids bonded to the Glycerol by an Ester link then, mono meaning one, a Monounsaturated Fat is formed.

If there are two or more unsaturated, double bonded, Fatty Acids in the mixture then, poly meaning many, a Polyunsaturated Fat is created. If all the Fatty Acids in the fat are single-bonded, saturated Fatty Acids, you guessed it, the Fat is a Saturated Fat.

Because the actual Fat is comprised of Fatty Acids, with various  melt points, different Fats, in different foods, melt at different temperatures. Lard, or Pork fat, is an example that melts at different temperatures.

Pork Back Fat melts between 84°F & 104° F (30° C to 40° C), pork Leaf Fat, from around the kidneys melts between 109° F & 118° F (43° C to 48° C)  and Mixed Pork Fat melts between 97° F & 113° F (36° C to 45° C). The cooking heat also has to penetrate all the way into where the fat resides to cause it to render or melt. Think Internal Temperatures when considering Rendering.

Some other food items and there Fatty Acid make up are listed below.