英语听力文摘 English Digest 318、无糖可乐的奥秘

　　How Do You Make A Diet-Coke Float?
你能让无糖可乐浮起来吗？
Here’s an at-home experiment you can try.
Take a can of “classic” Coca-Cola and a can of Diet Coke, and without opening either one submerge them in water. A deep sink or a bucket will do the trick. You’ll find the can of Diet Coke rises to the top, while the Classic Coke stays sunk. Can you guess why?
Why?
The answer lies in the chemical contents of the Diet Coke — in fact, in the very distinction that makes it “Diet”.
Although their ingredients are otherwise similar, Diet Coke is not made with real sugar: instead, the makers¹ of Coca-Cola products have replaced the sugar with a synthetic² chemical called Aspartame.
Aspartame, which is commonly known as Nutrasweet, is a kind of substitute sugar — intended

　　High Molecular³ Density⁴
Real sugar has a high molecular density. In other words you can think of sugar molecules⁵ as being thickly packed together.
This also means sugar molecules themselves will be relatively⁶ heavy, even when dissolved in solution. In the case of the sinking Coke, the real sugar content is acting⁷ as an anchor for the can.
Coca-Cola Taste
There’s also the fact that Nutrasweet is much sweeter than sugar, and so less is needed per can to achieve that recognizable Coca-Cola taste. Thus the bobbing Diet Coke not only has a lower average density, it also has a lower mass — there’s less “stuff” dissolved in the mixture. If you were an advertising⁸ executive, you might want to market diet sodas⁹ as “Light” — it wouldn’t be far from the truth.
你可以在家做这样的实验。
把没打开过的两听可乐（含糖，无糖）放在深槽或者高桶中，里面的水淹没两听可乐，你会发现无糖可乐浮在水面；而含糖可乐却沉下去了。你能猜到原因吗？
奥秘就在于无糖可乐的成分，这也是“无糖”的原因。虽然，无糖可乐和普通可乐的成分很相似，无糖可乐中添加的并非真正的糖，而是一种做“阿斯巴甜”的合成化学物。
“阿斯巴甜”是一种常见的代糖甜味剂，不含糖的热量却有糖的甜味。
高分子密度
真正的糖分子密度高，也就是说糖分子紧密地排列在一起。
即使溶解在溶液中，相同体积的糖更重。实验中沉下去的普通可乐，正是因为糖成分像锚般让罐子下沉。
可乐的味道
代糖比糖甜，所以更少的代糖能达到普通可乐的甜味。这样水中摇摆的无糖可乐不仅平均密度更低，质量也比普通可乐轻——因为更少的代糖溶解在可乐中。如果你是广告商，你可以这样宣传——无糖碳酸饮料的优点：轻。这可没有说大话。
m(质量）=p（密度）V （体积）

1 makers   

n.制造者，制造商（maker的复数形式）

参考例句：

• The makers of the product assured us that there had been no sacrifice of quality. 这一产品的制造商向我们保证说他们没有牺牲质量。
• The makers are about to launch out a new product. 制造商们马上要生产一种新产品。 来自《简明英汉词典》

2 synthetic   

adj.合成的，人工的；综合的；n.人工制品

参考例句：

• We felt the salesman's synthetic friendliness.我们感觉到那位销售员的虚情假意。
• It's a synthetic diamond.这是人造钻石。

3 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

4 density   

n.密集，密度，浓度

参考例句：

• The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
• The region has a very high population density.该地区的人口密度很高。

5 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

6 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

7 acting   

n.演戏，行为，假装；adj.代理的，临时的，演出用的

参考例句：

• Ignore her,she's just acting.别理她，她只是假装的。
• During the seventies,her acting career was in eclipse.在七十年代，她的表演生涯黯然失色。

8 advertising   

n.广告业；广告活动 a.广告的；广告业务的

参考例句：

• Can you give me any advice on getting into advertising? 你能指点我如何涉足广告业吗?
• The advertising campaign is aimed primarily at young people. 这个广告宣传运动主要是针对年轻人的。

9 sodas   

n.苏打( soda的名词复数 )；碱；苏打水；汽水

参考例句：

• There are plenty of sodas in the refrigerator. 冰箱里有很多碳酸饮料。 来自辞典例句
• Two whisky and sodas, please. 请来两杯威士忌苏打。 来自辞典例句