揽瓜阁做题小分队 第15天 铝的作用及价格演变-从天价到白菜价

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The most common metal in the Earth’s crust, aluminum (or aluminium) was not discovered until 1825 because its isolated state is so reactive that free nuggets or flakes of the metal are never found in nature; rather, the metal is typically found as part of an amalgam, most commonly bauxite ore. Moreover, elemental aluminum is extremely difficult—and expensive—to separate from its ores by traditional chemical means. Indeed, the extreme reactivity of aluminum helps protect its modern, ubiquitous manifestations, such as aluminum foil. The surface of pure aluminum instantly combines with atmospheric oxygen to form a thin but robust “passivization” seal of aluminum oxide that prevents further corrosion. Many other metals, such as iron, are less reactive than aluminum, but their superficial oxides do not form as swiftly, completely, or impermeably.

For several decades after its discovery, aluminum was considered a precious metal and was more costly than gold or platinum, not because of any fundamental scarcity, but because of its elevated cost of production. The price of aluminum suddenly plummeted in 1886, however, when two 23-year-old inventors independently developed an electrolytic process of separating pure aluminum from a bath of molten aluminum salts, primarily cryolite. Cryolite itself is rare enough that synthetic salts eventually replaced it as the solution medium.

1. What can be most logically inferred from the passage about iron?
(A) It corrodes more quickly than aluminum.
(B) Its oxides form more slowly and robustly than those of aluminum.
(C) It is cheaper to isolate from its ores by traditional chemical means than aluminum.
(D) It is more susceptible to passivization than is aluminum.
(E) It is more commonly found in its isolated, elemental state.

2. According to the passage, the natural passivization layer on the surface of aluminum metal
(A) causes atmospheric oxygen to react chemically with the metal
(B) is less impenetrable than typical iron oxide films formed on pure iron
(C) lowers the utility of aluminum in its uncontaminated state
(D) provides aluminum with a chemical advantage, relative to other metals

(E) precludes the inexpensive purification of the metal by traditional chemical processes

3. In terms of economic impact, which of the following hypothetical situations would be most analogous to what the passage indicates happened in 1886?
(A) Fossil remains of a previously unknown dinosaur species are simultaneously discovered by two researchers working independently of one another.
(B) Lead-acid batteries are widely replaced in automobiles by batteries containing lithium, a much rarer metal than lead.
(C) Direct processing of light signals within fiber-optic devices supplants electronic signal processing performed by solid-state transistors.
(D) After supplies of a widely used commodity become unavailable, the price of the commodity surges.
(E) Low-cost artificial synthesis of diamonds, which are expensive to mine but composed of the common element carbon, is perfected.

参考答案，做完才看 ：）

ADE

irisville

ade

Minato66666

A
B
E

Minato66666

less impenetrable 佛了

123Better

EDD

_Salaxy_

P1:地壳最常见的金属铝直到1825年才被发现，因为它分离状态过分活跃所以游离的铝很难在自然界存在。利用传统方法将铝元素从铁矿石中剥离难度很大成本很高。纯铝的表面有一层很薄但很粗糙的可以防止生锈的铝氧化物封层。其他金属比如铁就不如铝那么活跃，但他们的表面的氧化层并不像铝形成的那么快、完整且不易渗透。
P2:铝价格高不在于稀缺性，而是因为不断上涨的生产成本。然而直到1886年，两位23岁的发明家独立发明出一种分离纯铝的方法使得铝的价格骤降。

EAE

N0ire

5min
主旨：铝为什么一度非常稀有（属性+制造工艺）
P1: 铝含量高但非常活泼，常以化合物的形态出现，单质难以被分离，并且容易形成致密的氧化膜防腐蚀；
P2: 铝价因为量产困难而居高不下，直到电解铝的发现。

ADE

半日大哥

C D D
用时5分钟
1. 铝是地球上储量最丰富的金属。纯铝特别容易发生化学反应，所以自然界几乎没有铝单质存在，因此直到1825年铝元素才被发现。
2. 很多年以来铝很贵是因为很难生产，直到1886年两个年轻人应用了电解法。

xulexuan

bde

Sibaiyuan

ADE