从无机小分子生成有机小分子的阶段，即生命起源的化学进化过程是在原始的地球条件下进行的。需要着重指出的是米勒的模拟实验。在这个实验中，一个盛有水溶液的烧瓶代表原始的海洋，其上部球型空间里含有氢气、氨气、甲烷和水蒸汽等“还原性大气”。米勒先给烧瓶加热，使水蒸汽在管中循环，接着他通过两个电极放电产生电火花，模拟原始天空的闪电，以激发密封装置中的不同气体发生化学反应，而球型空间下部连通的冷凝管让反应后的产物和水蒸汽冷却形成液体，又流回底部的烧瓶，即模拟降雨的过程。经过一周持续不断的实验和循环之后。米勒分析其化学成分时发现，其中含有包括5种氨基酸和不同有机酸在内的各种新的有机化合物，同时还形成了氰氢酸，而氰氢酸可以合成腺嘌呤，腺嘌呤是组成核苷酸的基本单位。米勒的实验试图向人们证实，生命起源的第一步，从无机小分子物质形成有机小分子物质，在原始地球的条件下是完全可能实现的。

think about what you had for breakfast today. the packaging on any processed food you ate, including cereal, milk,bread and yogurt, has a label that provides you with nutrition information so you can make healthy diet choice. this imformation comes from chemical analysis.
suppose you ate a boiled egg and a banana instead of the cereal and milk. there is no label with nutrition information there, but analytical chemists have rested a sample of eggs and bananas for residues of harmful chemicals so you can be confident that your breakfast is safe to eat.
your toothpaste, too, will have a label that says something like 'active ingredient 0.7% w/w sodium monofluorophosphate'. an analytical chemist would have checked that this amount of active ingredient was correct.
analytical chemists are employed in a range of industries, from food manufacturing to environmental monitoring and foerensic sciences and many more. they use a range of techniques and technologies to determine the identity, quality, and quantity of the chemicals that make up our world.
the composition of consumer goods is of great importance. for example, residues such as dieldrin and DDT have been detected in meat. nutrionists urge us to eat fish on a regular basis to take advantage of the beneficial fatty scids that many fish contain. but fish can also contain heavy metals, such as mercury. goernments have placed restrictions on the amount of pesticides and heavy metals allowed in foods. for example, the acceptable daily intake of DDT is 0.002 milligram per kilogram of body weight per day(0.002mg/kg/day) while that of dieldrin is 0.0001mg/kg/day

还是自己写好了，因为这些需要自己经历过写出来才是最真实的，不管好坏只要对得起自己就够了。