Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: Water has remarkable properties. Water expands when it freezes, even though all other substances contract. This means that in the winter ice on a pond or lake will float. Water has high surface tension because polar molecules tend to stick together. That's why drops stick together or some bugs can walk on the surface of a pond. Without water, life might not be able to exist on Earth. If it did exist, it would not be as diverse or as complex. Answer: polar molecules sticking together
A:
What can water's high surface tension be attributed t?