Can someone explain fractional distillation of crude oil to me like I’m a 5 year old

[Lolalaal]

DD has a test next week and I want to shoot my self in the head.

Why is it hot at the bottom but cool at the top?! Heat rises no?!

The heater is at the bottom!

Crude oil goes in at the bottom and is heated up until it evaporates. The gas travels up the distillation column and condenses at different levels, depending on their boiling point, the longer hydrocarbons, fuel oil for ships etc at the bottom and the smaller ones travel to the top methane remains as a gas.

We use this in class:

It's basically to do with boiling points. The boiling point of a substance is the temperature at which it converts either from a liquid to a gas or condensed from a gas to liquid.

The crude oil is heated before entering the fractionating column. The different compounds then cool down and are collected in fractions as liquids (mostly) depending on their boiling points.

You are right about the temperature in the column. Cooler at the top and hotter at the bottom.

The smaller molecules will condense into liquids at cooler temperatures at the top of the column, whereas larger molecules condense at higher temperatures towards the bottom. The relationship between molecule size and boiling point is also important in the fractionally distillation of crude oil.

Thank you thank you thank you!!!

Crude oil is hot when it comes out of the earth (even if the earth is under the sea). I was once told it does not come out in liquid form but I now can't explain why so I might have got that wrong.

re heat rises:

If you put your hand over your kitchen hob when it is on, where is it hottest? Right close to the hob, or 2 feet above?

Hot air rises as it is less dense than cold air (because air expands when heated), but as it rises away from the heat source, it gradually cools.