我在新加坡有个表妹。在我所有的表兄弟姐妹之间,她是最小的,也是跟我的家人最亲密的。
她年龄跟文选一样,所以今年就读中三。我来到新加坡降级到中三,造成我们两人都读同一年。她是个音乐天才。小时候开始学钢琴,老师觉得她很厉害,可以开始学第二种乐器,就选了小提琴。她学小提琴已经到ABRSM Grade 8了,所以现在开始学竖琴。我去看Phantom of the Opera时,她刚好也在。关于学业,她很用功。她有我缺乏的好习惯,就是一致性……
她选修Pure Science,跟我们所谓的理科班一样。我也是属于Pure Science,只不过没有学生物。因此,当她遇到问题时,她会来找我。
她平时会问我关于物理的问题,不过今天,当我在弹钢琴时,她打电话。
她正在准备化学考试,发现自己对摩尔的概念有所困难。如果她去年问我的话,我肯定无法教她=P 幸亏我今年对化学的了解有很大的进步。
首先,我教她相对原子质量(Ar)。我告诉她关于科学家为了以最简单的办法测量原子的质量,就把所有的元素的质量跟最小的原子打个比方。因此,氢,属于最小的原子,就有Ar=1。可是科学家发现氢很难用,就找别的,更容易用的元素代替。结果,他们就用碳-12的同位素的质量的12分之1。这个概念,我必须重复几次她才明白。过后就接下去解释相对分子质量与相对方程式质量。
后来,我就遇到了当时最难让她开窍的概念,就是摩尔……
我: Now let's move on to The Mole. This is the most important component of the entire chapter, so make sure you get this right.
表妹: Ok.
我: Ok, first of all, you know what a Mole is right? It is 6 X 10^23. Now this is how it came about: Scientists were looking for a convenient way in which they could convert Relative Atomic Mass into Mass. They found that by using the Mole, they could do so. By taking 1 Mole of an atom, they would get the number of grams times its Relative Atomic Mass!
表妹: Errr...
我: Erm, let's try that again, back from the beginning. Scientists discovered that whenever there are 6 X 10^23 nucleons, which are protons and neutrons, you would get 1 gram! Understand?
表妹: Uh... huh.....
我: You remember what a nucleon is right? A nucleon is either or a proton or a neutron. Remember the structure of an atom? A nucleous surrounded by electrons. The nucleous contains nucleons, which are protons and neutrons.
表妹: Yes.
我: Ok, now remember what the Relative Atomic Mass is. It's also the Nucleon number right? Meaning that itbv is the number of neucleons in the atom right?
表妹: Uh... huh.....
我: Now, remember what I told you earlier, 1 Mole of nucleons is 1 gram right? So, when you take 1 Mole times the Relative Atomic Mass of the atom, you will get the value of the Ar in grams, because the Ar is also the number of nucleons!
表妹: Huh???
我: Ok, let's go back to the beginning......
就这样,一直重复。她还问我开始拔头发了没……我吸一大口气。我也知道我教人的技巧不大有效(问傅米就知道了)。我只好慢慢地重复,把句子改一改,也提出一些历史,例如Avogrado如何得到摩尔的数值。她还是不能开窍。她已经明白质子、中子、相对原子质量与质量互相连起来了,不过还不能把摩尔拆进去。最后,我用数学概念解释。
我: Erm, let me try using Mathematics to help you understand. Have you learnt proportions?
表妹: What's that?
我: Ei? I thought you learnt it before? I learnt it in Sec2...
表妹: Err...
我: Uh... something like when x is proportional to y, we can write the equation x = ky, remember?
表妹: Oh! I remember something like that, but we learnt y = kx.
我: (-_- " )
表妹: Haha.
我: Well, think of of this relationship like y = kx!
表妹: 哦!!!!!!!
我: Get it? So what's your Y?
表妹: Mass!
我: What's your X?
表妹: Relative Atomic Mass!
我: And your k?
表妹: The Mole!
我: That's right!
表妹: 哦!!!!!!! I get it now! I think I'll read the text book now. If I have any more questions, I'll call you later. Thank you so much!!! Bye!
我: Bye.
唉……电话都湿了。
我发现,当你问一个人他明白不明白,他答“明白”的话,很可能是不明白。如果他答“哦!!!” 的话,就肯定明白了。
没有数学的话,我早都死了……