Why do alcohols have such low freezing points?
In: Chemistry
Compared to something like water, the interactions between molecules of alcohol are very weak.
Temperature of a substance is proportional to the amount of movement that it’s molecules have.
In order to freeze a substance, you must bring it to a low enough temperature that the molecules stick together. Likewise, boiling or melting a substance requires heating it until the molecules are moving too fast to stick together.
In the case of alcohol, it’s interactions are very weak, so the molecules must be moving much slower in order to interact and stick together. Water has very strong interactions between molecules, so they will stick together easier when moving at higher speeds. Likewise, it will take more heat to boil or melt water because the molecules don’t want to become unstuck
Alcohol (ethanol) doesn’t freeze like water for example because there are less hydrogen atoms bonded to oxygen atoms in ethanol. This makes alcohol less able to hydrogen bond, which is what holds the molecules tight together in ice.
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