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Why does milk overflow when boiled ?
Question Date: 2013-04-22
Answer 1:

Good question! You may have noticed that when you boil milk, it overflows, unlike water. The reason is that milk isn't really a proper "liquid" by the chemical definition; milk is what's called a colloidal suspension. That means that there are plenty of substances in milk that form microscopic particles that just float around. In particular, milk contains small particles of fat. Now, when you heat up milk, some of these particles end up floating to the top of the milk and form a thin film. When the milk boils, the steam can't escape (as it does in water) because it's trapped by the film, and this is what causes the milk to overflow.

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