化学风化将岩石材料的成分改变为表面矿物,例如粘土。它会攻击在表面条件下相对不稳定的矿物质,如玄武岩,花岗岩或橄榄岩等火成岩的主要矿物。它也可能发生在沉积岩和变质岩中,是腐蚀或化学侵蚀的一个元素。化学风化不会通过风,水和冰(这是物理风化)将岩石破碎成较小的碎片。它也不会通过植物或动物的作用(即生物风化)将岩石分开。相反,它通常通过碳酸化,水合作用,水解或氧化来改变岩石的化学成分。水通过裂缝引入化学活性剂并使碎石碎片化是特别有效的。水也可能使材料的薄壳松散(在球状风化中)。化学风化可能包括浅层,低温蚀变。当由于大气二氧化碳(CO2)而天然呈微酸性的降雨与碳酸钙(CaCO3)(例如石灰石或白垩)结合时发生碳酸化。相互作用形成碳酸氢钙或Ca(HCO3)2。雨的正常pH值为5.0-5.5,单独酸性足以引起化学反应。酸雨是由大气污染引起的非自然酸性,其pH值为4(较低的数字表示较大的酸度,而较高的数字表示较大的碱度)。碳化,有时也被称为溶解,是岩溶地貌的落水洞,洞穴和地下河流背后的驱动力。当水与无水矿物反应时会发生水合作用,形成新的矿物质。将水加入矿物的晶体结构中,形成水合物。无水石膏,意为“无水石”,是一种硫酸钙(CaSO4),通常在地下环境中发现。当暴露在表面附近的水中时,它很快就会变成石膏,这是莫氏硬度标度上最柔软的矿物质。水解与水合作用相反;在这种情况下,水会分解矿物的化学键,而不是产生新的矿物质。这是一种分解反应。这个名称使这个特别容易记住:前缀“hydro-”表示水,而后缀“ – 析”表示分解,分解或分离。氧化是指氧与岩石中的金属元素反应形成氧化物。一个容易识别的例子就是生锈。铁(钢)容易与氧气反应,变成红褐色的铁氧化物。这种反应是造成火星红色表面的原因。赤铁矿和磁铁矿是另外两种常见的氧化物;你可以在这个画廊找到。

加拿大卡尔加里大学化学Assignment代写:化学风化

Chemical weathering alters the composition of the rock material toward surface minerals, such as clays. It attacks minerals that are relatively unstable in surface conditions, such as the primary minerals of igneous rocks like basalt, granite or peridotite. It can also occur in sedimentary and metamorphic rocks and is an element of corrosion, or chemical erosion. Chemical weathering does not break rocks into smaller fragments through wind, water and ice (that’s physical weathering). Nor does it break rocks apart through the action of plants or animals (that’s biological weathering). Instead, it changes the chemical composition of the rock, usually through carbonation, hydration, hydrolysis or oxidation. Water is especially effective at introducing chemically active agents by way of fractures and causing rocks to crumble piecemeal. Water may also loosen thin shells of material (in spheroidal weathering). Chemical weathering may include shallow, low-temperature alteration. Carbonation occurs when rain, which is naturally slightly acidic due to atmospheric carbon dioxide (CO2), combines with a calcium carbonate (CaCO3), such as limestone or chalk. The interaction forms calcium bicarbonate, or Ca(HCO3)2. Rain has a normal pH level of 5.0-5.5, which alone is acidic enough to cause a chemical reaction. Acid rain, which is unnaturally acidic from atmospheric pollution, has a pH level of 4 (a lower number indicates greater acidity while a higher number indicates greater basicity). Carbonation, sometimes referred to as dissolution, is the driving force behind the sinkholes, caverns and underground rivers of karst topography. Hydration occurs when water reacts with an anhydrous mineral, creating a new mineral. The water is added to the crystalline structure of a mineral, which forms a hydrate. Anhydrite, which means “waterless stone,” is a calcium sulfate (CaSO4) that is usually found in underground settings. When exposed to water near the surface, it quickly becomes gypsum, the softest mineral on the Mohs hardness scale. Hydrolysis is the opposite of hydration; in this case, water breaks down the chemical bonds of a mineral instead of creating a new mineral. It is a decomposition reaction. The name makes this one particularly easy to remember: The prefix “hydro-” means water, while the suffix “-lysis” means decomposition, breakdown or separation. Oxidation refers to the reaction of oxygen with metal elements in a rock, forming oxides. An easily recognizable example of this is rust. Iron (steel) reacts easily with oxygen, turning into reddish-brown iron oxides. This reaction is responsible for the red surface of Mars. Hematite and magnetite are two other common oxides; you can find both in this gallery.

发表评论

电子邮件地址不会被公开。 必填项已用*标注