點解個test tube要downwards?(解決了)謝謝大家@@

卍拉帝亞斯卍

明白了@@"..唔該哂大家[[onion_43]]

ｑ大財神ｐ

As the steam will condense near the mouth of test tube to form water droplet and drop along the test tube to the bottom.
The water droplets will crack the hot tube.