一天，爸爸叫我打水给他喝。我去的时候，给爸爸打了一大瓶水，看见水都超出了瓶口，“爸爸，快来帮我一下。”我说。于是，爸爸走过来，问：“你知道为什么水都已经超过了瓶口，却不会溢出来呢？”我听了，用怀疑的眼光看着爸爸，接着，爸爸说：“是因为水到在瓶子的表面会产生一种张力，这种张力是往中心的，因此我们看起来以为水会溢出来，其时不是。”

One day, my father asked me to fetch water for him. When I went, I gave Dad a big bottle of water, and saw that the water was beyond the mouth of the bottle, "Dad, come and help me." I said. So Dad came up and asked, "do you know why the water has passed the bottle mouth, but it will not overflow?" I listened and looked at Dad with suspicion. Then Dad said, "it's because when the water comes to the surface of the bottle, there will be a kind of tension. This tension is toward the center, so we seem to think that the water will overflow. At that time, it's not."

我听了是懂非懂，原来水为什么在超过瓶子口的地方却没有流下来的原因，就是因为有表面张力。

I understand. The reason why water doesn't flow down beyond the bottle mouth is because of the surface tension.