溫度計問題

Question

1.The lengths of the mercury columns of two mercury-in-glass thermometers are the same at 0 degree. However, when they are placed in the same beaker of warm water, the lengths of the mercury coloums are different. Suggest two possible answers.
點解係0 度一樣, 但其他唔一樣既?
2We should not use boiling water to sterilise a liquid-in-glass clinical thermometer.Why?

Answer 1

1. The cross-sectional area of the stems of the two thermometers are different.
The volume of mercury in the bulb of the two thermometers are different.

2. There is a restriction between the bulb of mercury and the stem. When placed in hot water, rapid expansion of mercury may burst the bulb due to the presence of the restriction.

Answer 2

1. 那是 constriction 不是 restriction，中譯頸縮。
2. 因為 liquid-in-glass clinical thermometer 的量度範圍只在 37°C 上下數攝氏度。假如用100°C的沸水消毒，玻璃管便會因測溫液體的膨脹而損壞。

Answer 3

1. 溫度計之玻璃泡是儲存水銀及感應溫度變化，而玻璃管則是用來顯示溫度。在製造水銀溫度計時，當注入水銀後，才訂定刻度，先得出0度(0度是基準刻度)，再求100度刻度，其餘度數則是平均刻上。因為玻璃管及玻璃珠在製造時都會有多少出入，因此每支溫度計都應獨立測試。
2. clinical thermometer 因為要顯示較精細之刻度，所以改以酒精代替水銀(酒精之體積彭脹比例，比水銀高很多)，而酒精之boiling point 遠低於100度，所以不能量度boiling water。