Whether molecules are solid, liquid or gas depends on how they interact with one another (intermolecular forces or IMFs). Butter is mostly a form of fat called a triglyceride. The longish (18 atom) carbon chains like hanging around with each other so the IMFs are very high. This makes the butter solid.
We don’t see this in something like milk because the fats are a lot more spread out (dispersed) in water so we don’t get lots of them hanging out together until the milk goes bad and the fats and water separate.
Latest Answers