In this video, we'll take a look at our second physical property of fatty acids, Melting Point. Now, here we're going to say Carbon Chain Length and the number of Pi Bonds have opposing effects on the melting point of fatty acids. Here, when we take a look at Carbon Chain Length, we're going to say that Length is directly proportional to Melting Point. Meaning that if we increase our Carbon Chain Length, then we're going to increase our melting point. If we take a look here at this graph, we have our Temperature on the y-axis, and number of carbons on our x. And we can see that as our number of carbons increases, our temperature or melting point increases. Here we have 12 carbons, 16 carbons, 20, and 24 carbons. Here we have our lauric acid, we have palmitic acid, here we have arachidonic acid, and we have lignoceric acid. And we can see as the number of carbon chains increases, the temperature is going up.

On the opposite side, we see the opposite occur. Here we're going to say the number of Pi bonds is inversely proportional to melting point, meaning that if I increase the number of Pi bonds, I'm going to decrease my melting point. If we take a look here, we have stearic acid which is well over 60 degrees Celsius in terms of temperature. Just adding 1 pi bond to go to Oleic acid causes a sharp decrease within our melting point. Oleic Acid here is somewhere around 11 to 13 degrees or so in terms of melting point. And if we add another pi bond, now we have 2 where we have Linoleic acid, it's going to go below 0 degrees Celsius in terms of melting point. So here we can see a great precipitous drop in our melting point as the number of Pi Bonds increases.

So remember, there is an opposite effect. Increasing the carbon chain length increases my melting point. Increasing the number of pi bonds decreases my melting point.