📚 Mixtures | 混合物
In KS3 chemistry, a mixture is a physical combination of two or more substances that are not chemically bonded together. Each substance keeps its own properties, and mixtures can usually be separated by physical methods.
在 KS3 化学中，混合物是两种或两种以上物质通过物理方式组合在一起、没有发生化学键合的物质。每种物质都保持自身性质，混合物通常可以用物理方法分离。
1. What Is a Mixture? | 什么是混合物？
A mixture is made when two or more substances are put together but no chemical reaction happens. For example, mixing sand and salt gives a mixture: you can still see the two solids, and no new substance is formed. Air is also a mixture of gases such as nitrogen (N₂), oxygen (O₂), argon (Ar) and carbon dioxide (CO₂).
当两种或两种以上物质放在一起但没有发生化学反应时，就形成了混合物。例如，把沙子和盐混合得到一种混合物：你仍然能看到两种固体，而且没有新物质生成。空气也是一种气体混合物，含有氮气（N₂）、氧气（O₂）、氩气（Ar）和二氧化碳（CO₂）等。
The substances in a mixture are not joined by chemical bonds. This means they can be separated using their different physical properties, such as particle size, boiling point or solubility. Because there are no fixed proportions, the amounts of each substance in a mixture can vary.
混合物中的物质不是通过化学键结合在一起的。这意味着可以利用它们不同的物理性质（如颗粒大小、沸点或溶解度）进行分离。由于没有固定的比例，混合物中每种物质的含量可以变化。
2. Mixtures vs Pure Substances | 混合物与纯净物的区别
A pure substance contains only one type of particle. Elements and compounds are pure substances. A mixture contains at least two different substances that are physically mixed. For example, pure water contains only H₂O particles, while seawater is a mixture of water, salt and other minerals.
纯净物只含有一种粒子。单质和化合物是纯净物。混合物至少含有两种不同的物质，它们只是物理混合。例如，纯水只含有 H₂O 粒子，而海水是水、盐和其他矿物质的混合物。
Pure substances have sharp melting and boiling points, but mixtures often melt or boil over a range of temperatures. This difference helps us test whether a sample is pure. In the lab, if a solid melts over several degrees instead of at one temperature, it is probably a mixture.
纯净物有固定的熔点和沸点，但混合物往往在一个温度范围内熔化或沸腾。这个区别有助于我们检验样品是否纯净。在实验室中，如果一种固体在几度的范围内熔化而不是在某个固定温度熔化，它可能就是混合物。
3. Types of Mixtures: Homogeneous and Heterogeneous | 混合物的类型：均匀与非均匀
Mixtures can be classified as homogeneous or heterogeneous. A homogeneous mixture looks the same throughout, such as salt solution or clean air. A heterogeneous mixture has visibly different parts, such as a salad, sand in water or oil and water.
混合物可分为均匀混合物和非均匀混合物。均匀混合物整体看起来一样，例如盐水或洁净空气。非均匀混合物有肉眼可见的不同部分，例如沙拉、水中的沙子或油和水。
In a homogeneous mixture, the particles are evenly spread, so you cannot see the separate components. In a heterogeneous mixture, you can often identify the different materials because they are not evenly mixed. Knowing the type of mixture helps you choose how to separate it.
在均匀混合物中，粒子均匀分布，因此你看不到单独的组分。在非均匀混合物中，你通常能识别出不同的物质，因为它们没有混合均匀。了解混合物的类型有助于选择分离方法。
4. Solutions: Solute and Solvent | 溶液：溶质与溶剂
A solution is a homogeneous mixture of a solute dissolved in a solvent. The solute is the substance that dissolves, and the solvent is the liquid that does the dissolving. In salt water, salt is the solute and water is the solvent.
溶液是溶质溶解在溶剂中形成的均匀混合物。溶质是被溶解的物质，溶剂是进行溶解的液体。在盐水中，盐是溶质，水是溶剂。
Solutions are transparent, meaning light can pass through them, and they do not separate on standing. The solute may be a solid, liquid or gas. Carbonated drinks are solutions of carbon dioxide gas dissolved in water. Solubility is the mass of solute that can dissolve in a given amount of solvent at a certain temperature.
溶液是透明的，光线可以通过，而且静置时不会分层。溶质可以是固体、液体或气体。碳酸饮料是二氧化碳气体溶解在水中的溶液。溶解度是在一定温度下，一定量溶剂中能溶解的溶质质量。
5. Suspensions and Colloids | 悬浮液与胶体
A suspension is a heterogeneous mixture in which solid particles are spread through a liquid or gas but are large enough to settle out over time. Muddy water is a suspension: the soil particles sink to the bottom when left to stand.
悬浮液是一种非均匀混合物，其中固体颗粒分散在液体或气体中，但颗粒足够大，时间长了会沉降下来。泥水就是一种悬浮液：静置后泥土颗粒会沉到底部。
A colloid is a mixture with particles larger than those in a solution but smaller than those in a suspension. Colloids often look cloudy but do not settle quickly. Milk and fog are examples. KS3 usually focuses on solutions and suspensions, but recognising colloids helps explain everyday mixtures.
胶体是一种混合物，其中的颗粒比溶液中的大，但比悬浮液中的小。胶体通常看起来浑浊，但不会很快沉淀。牛奶和雾都是胶体的例子。KS3 通常重点学习溶液和悬浮液，但认识胶体有助于解释日常混合物。
6. Why Separation Matters | 为什么分离很重要
We separate mixtures to obtain useful materials, remove impurities or recycle substances. For example, drinking water is purified by removing mud, bacteria and salt. Crude oil is separated into fuels such as petrol and diesel.
我们分离混合物是为了获得有用物质、去除杂质或回收物质。例如，饮用水通过去除泥土、细菌和盐来净化。原油被分离成汽油和柴油等燃料。
Separation techniques rely on physical properties, not chemical reactions. This means the substances themselves do not change into new substances during separation. Choosing the best method depends on the properties of the components in the mixture.
分离技术依赖物理性质，
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