How does hydrogenated oil solidify more easily by having 'kinks' in them (the molecules)?

Question

I've been given the task:
'Hydrogenated oil has molecules that don't have kinks in them. Draw and label diagrams to show how this means they will solidify more easily.'
Help! I really don't understand

Answer 1

I'm not sure which part you don't understand so I will try to explain both.

Unsaturated, or nonhydrogenated, oils have kinks in them because they have double bonds. All oils have kinks, like this: /\/\/\/\. But most can rotate around all the bonds, so they act pretty much as though they were straight. An unsaturated oil has a double bond in it: /\/\/\\/\. It can't rotate around that double bond, so the kink stays in place. Most unsaturated oils also change the direction they zigzag in at the double bond like this: /\=/\ and that kinks it up even more.

Now, as for why that makes unsaturated oils liquid (and, by extension, what makes saturated oils solid), it's because saturated oils can pack together more closely. Without those kinks to get in the way, they can squeeze in really tight and solidify. Unsaturated oils can't get that close because of the kinks in their structure, so they don't solidify as easily.

Answer 2

Since they have kinks they can' t "lay" on each other at room temp. That is why they are liquid. It is like a sticks with alot of branches. In order to pack them closely you need to press them harder together. The kinks hinder close packing, and keep them "fluid".