Why can homonuclear molecules be gasses at STP, but be liquids when they are combined?

Question

For example, H2O.

In: Chemistry

Answer 1

Because that’s the way chemistry works.

I assume the reason you’re asking this is that you have an intuition that when you combine two similar objects the combination is also similar. While this is often true, it’s not true for chemistry. Chemistry is full of examples of combining two objects and getting one with wildly different properties. That’s just how chemistry works.