when the water is boiled, some steam would br formed

the steam moves upwards and the steam formed water drop

the water drop moves downwards

→ the steam disappear 1.because the water drop moves downwards
                                   2. 當然另一個原因係D steam 蒸發

我E個假設correct?

55
The second point of the hypothesis is not so clear. I think "The steam go to somewhere else" will be better.
The first point is not so clear too ^_^"
The steam condensed and become water drops will be better

什麼是d steam 蒸法==

另一個問題係~~
D學生問:「點解D steam 會消失左?」
D老師/ test bk 就答:「因為被蒸發lo」

點解唔講係關water drop o既事??

first, your hypothesis isn't an assumption at all. According to your argument, this phenomena only appears in one condition which is airtight container.

Second, you are missing one main component - Air


Third, when the environment is sealed like airtight container. hot air mix up with colder air ( when you open up the cover) instantly (within 0.1 sec), then vapor is produced through this circumstance.when you open up the cover of container. many water drop were formed because amount of air (colder temperature) got into the container  inside and cool down the hot air. the steam "disappear" because "steam" never being existed under airtight container (unless you open up the cover to let colder air getting inside).


conclusion: your statement and your "assumption" is wrong completely.