短文一

The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons. The electrons of an atom are bound to the nucleus by the electromagnetic force. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it is positively or negatively charged and is known as an ion. An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons determines the chemical element, and the number of neutrons determines the isotope of the element.

原子是物质的基本单位，由密集的中央核周围有云带负电荷的电子。原子核包含一个组合的带正电的质子和电中性的中子。一个原子的电子被电磁力约束的核。原子含有相同数目的质子和电子是电中性的，否则它是正或负电荷，称为离子。根据其原子核的质子和中子的数量分类：质子数决定元素，而中子数决定元素的同位素。

短文二

Analytical chemistry is the study of the separation, identification, and quantification of the chemical components of natural and artificial materials. Analytical methods can be separated into classical and instrumental. Classical methods use separations such as precipitation, extraction, and distillation and qualitative analysis by color, odor, or melting point. Quantitative analysis is achieved by measurement of weight or volume. Instrumental methods use an apparatus to measure physical quantities of the analyte such as light absorption, fluorescence, or conductivity. The separation of materials is accomplished using chromatography, electrophoresis.

分析化学是研究的分离，鉴定，以及自然和人工材料的化学成分定量分析。分析方法可分为经典和仪器。传统的方法使用的分离，如沉淀，萃取，蒸馏和定性分析的颜色，气味，或熔点。定量分析是以重量或体积测量的实现。仪器方法使用一个测量装置的被分析物，如光吸收，荧光的物理量，或电导率。材料的分离是通过使用色谱法，电泳。

短文三

Chromatography is a separation and analysis technique. The mixture is dissolved in a fluid called the mobile phase, which carries it through another material called the stationary phase. The various constituents of the mixture travel at different speeds, causing them to separate. The separation is based on differential partitioning between the mobile and stationary phases. Subtle differences in a compound's partition coefficient result in differential retention on the stationary phase. Chromatography may be preparative or analytical. The purpose of preparative chromatography is to separate the components and further get purified components. Analytical chromatography is done normally with smaller amounts of material and is for measuring the relative proportions of analytes in a mixture.

色谱是一种分离和分析技术。混合物溶解于流体称为流动相，进行通过另一种物质称为固定相。在不同速度下的混合各种成分的旅行，使他们分开。分离是基于差分移动和固定相之间的分配。在固定相的化合物的分配系数产生微分保持微妙的差异。色谱法可制备或分析。制备色谱的目的是分离的组件，进一步得到纯化的成分。解析法是通常与少量的物质是混合物中测量分析物的相对比例。

短文四

A buffer is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. Its pH changes very little when a small amount of strong acid or base is added to it and thus it is used to prevent changes in the pH of a solution. Buffer solutions are used as a means of keeping pH at a nearly constant value in a wide variety of chemical applications. Many life forms thrive only in a relatively small pH range so they utilize a buffer solution to maintain a constant pH. One example of a buffer solution found in nature is blood.

缓冲溶液由弱酸及其共轭碱或弱碱及其共轭酸的混合物。pH值的变化非常小，当少量的强酸或碱加入它，因此它是用来防止在溶液pH的变化。缓冲溶液作为pH值保持在多种化学应用的一个几乎恒定的值的方式。许多形式的生命茁壮成长，只在一个相对较小的pH值范围内，所以他们利用保持恒定的pH缓冲溶液的一个例子在自然界中发现的缓冲溶液是血。

短文五

A molecule is an electrically neutral group of two or more atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their lack of electrical charge. A molecule of a substance cannot be seen by the naked eye - a drop of water is made up of many, many molecules of water.

Scientists believe that molecules are always moving. They can be solids, liquids or gases. Molecules move the most and are the furthest apart when they are gases. Molecules are closest together and move the most slowly when they are solids. Molecules that are liquids movement is between those of gases and those of solids.

Molecules come in different sizes and molecular weights. Their atoms can be arranged in different ways. Molecules in substances can be split up in chemical reactions to form other molecules. They can also recombine into larger molecules or be broken down into smaller molecules.

一个分子是由化学键结合在一起的两个或两个以上的原子的电中性的组。分子与离子的电荷的缺乏。一种物质不能分子被肉眼看到一滴水是由许多，许多水分子。

科学家认为，分子总是在不断地运动。他们可以是固体，液体或气体。分子移动最是最远时，气体。分子是最接近的移动最慢时，固体的。分子，液体运动的气体和固体之间的。

分子有不同的大小和分子量。他们的原子可以在不同的排列方式。分子物质可分成化学反应形成其他分子。他们还可以组合成更大的分子或被分解成更小的分子。

短文六

Liquid is one of the four fundamental states of matter (the others being solid, gas, and plasma), and is the only state with a definite volume but no fixed shape. A liquid is made up of tiny vibrating particles of matter, such as atoms and molecules, held together by intramolecular bonds. Water is, by far, the most common liquid on Earth. Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly constant density. A distinctive property of the liquid state is surface tension, leading to wetting phenomena.

The density of a liquid is usually close to that of a solid, and much higher than in a gas. Therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, they are both called fluids. Although liquid water is abundant on Earth, this state of matter is actually the least common in the known universe, because liquids require a relatively narrow temperature/pressure range to exist.

液体是物质的四种基本状态（其它是固体，气体，等离子体），并且是唯一的国家有一定的体积，但没有固定的形状。液体是由物质的微小振动的粒子，如原子和分子，通过分子内的键连接在一起。水是，迄今为止，地球上最常见的液体。如气体，液体可以流动，容器的形状。一些液体抵抗压缩，也可以压缩。不同于气体，液体不散的填充容器的每一个空间，并保持相当恒定的密度。的液体状态的独特性质是表面张力，导致润湿现象。

液体的密度通常是接近的固体，并远远高于在气。因此，液体和固体都称为凝聚态物质。另一方面，作为液体和气体的份额流动的能力，他们都被称为流体。虽然液态水是丰富的地球上，这种状态的物质在已知的宇宙中，实际上是最常见的，因为液体需要一个相对窄的温度/压力范围内存在。