Hydrogen and water

You may find it interesting that hydrogen and water use the same prefix. It is:

hydr(o)-

Actually it is related to how hydrogen was discovered.

Hydrogen was discovered by Henry Cavendish. He collected the air bubbles from metal-acid reaction and found this air to be inflammable. He named it "inflammable air", which later was given the name hydrogen by Antoine Lavoisier. Lavoisier name it hydrogen because he obtained water after burning hydrogen. The word "hydrogen" means "substance that produces water" (please refer to Lesson 16-5 for the suffix -gen).

 Cavendish's apparatus for making and collecting hydrogen. Source : Wikipedia

Henry Cavendish was a notoriously shy man, some even postulated that he suffered from autism. However, he achieved a lot.

Henry Cavendish. Source: Wikipedia

Although Cavendish was not the first person to discovered the air bubbles from metal-acid reaction, he was the first person who collected the air and characterized them. Therefore, he was recognized as the person who discovered hydrogen. He also discovered carbon dioxide by dissolving alkali in acids.

中文版

氫（hydrogen）跟水（water）有什麼關係？

應該也有同學注意到，元素「氫」（第十七課（一））與化合物「水」（第十七課（二））共用了專業字首：

hydr(o)-

雖然水的化學式是H₂O，的確有氫啦！但是也有氧啊！為什麼水的字首不用跟氧相關的字？或者說，為什麼氫的字首要跟水相關？

這就有故事要說了。先說氫的發現：氫氣是由卡文迪什（Henry Cavendish）發現的，他將金屬片溶在強酸裡，產生的氣泡就是氫氣。雖然也有其他人比他先做這個實驗，但是他是第一個把這些氣體收集起來，發現氫氣可以燃燒的人。

卡文迪什收集氫氣的裝置。圖片來源：wiki

因為氫氣很容易燃燒，所以他把氫氣叫做「易燃空氣」（inflammable air）。「氫氣」（hydrogen）這個名字是拉瓦節（Antione Lavoisier）命名的，因為氫氣燃燒後產生水，所以拉瓦節為氫氣取名為hydrogen，是「水」hydr(o)-與「產生」-gen的合體（第十六課（五）），意思就是「產生水的物質」。

卡文迪什也發現二氧化碳。他將鹼溶在酸中，得到的氣泡就是二氧化碳。