🧃 纯净物与混合物：一种还是好几种🧃 Pure Substances & Mixtures: One or Several
上一片，⚗️ 小烧瓶弄清了原子们靠什么"胶水"黏在一起。这一片它拿起放大镜，对准实验室的瓶瓶罐罐：为什么水是"独唱"，空气却是"合唱"？Last leaf, ⚗️ Little Flask learned what "glue" holds atoms together. Now it turns a magnifier on the lab shelves: why is water a solo, while air sings in a choir?
第 1 步：放大镜下的两杯液体Step 1: Two glasses under the magnifier
怎么看出一种物质还是好几种？小烧瓶把放大镜凑近两杯液体。How do we tell one kind of stuff from several? The flask holds its magnifier over two glasses.
放大镜往清水里一看：游来游去的只有水分子 H₂O 一个品种——这是纯净物，里面只有一种物质。再看果汁：水分子、糖分子、果酸分子、色素分子挤成一团，好几个品种——这是混合物。纯净物像独唱，混合物像合唱。Under the magnifier, clear water shows only one kind of swimmer — water molecules, H₂O. That is a pure substance: just one kind of thing inside. Juice is different: water, sugar, fruit-acid and color molecules crowd together — a mixture. A pure substance is a solo; a mixture is a choir.
那看不见也摸不着的空气呢？它算独唱还是合唱？What about air, which we can't even see? A solo or a choir?
第 2 步：空气的合唱团Step 2: Air's choir
把空气成分画成一块饼：氮气约 78%、氧气约 21%，剩下 1% 是氩气、二氧化碳、水蒸气等。一口吸进去的是一整支合唱团——所以空气是混合物。而氧气瓶里的氧气只有 O₂ 一位歌手，是纯净物。同一种物质：装在瓶里是独唱，散进空气中就成了合唱的一员。Slice air into a pie: about 78% nitrogen, 21% oxygen, and the last 1% argon, carbon dioxide, water vapor and more. One breath pulls in a whole choir — so air is a mixture. Oxygen in a tank is one singer alone, O₂: a pure substance. Same substance: a solo in the tank, one voice in the choir out in the air.
混在一起的东西，还能再分开吗？Can a mixture ever be taken apart again?
第 3 步：把合唱拆回独唱Step 3: Splitting the choir back into solos
能！先见识三招：泥沙水倒进漏斗，滤纸把泥沙拦住、清水滴下去——过滤；盐水放在蒸发皿里加热，水跑掉、盐留下——蒸发；想连水也收回来，就把它烧成蒸汽再冷凝回水——蒸馏。这些物理办法不产生新物质，也正是混合物只是"拌"在一起的证据。Yes! Three first moves: pour muddy water through a funnel — the filter paper traps the mud while clear water drips through (filtering); heat salt water in a dish — the water leaves and the salt stays (evaporation); to catch the water too, boil it into steam and cool it back (distillation). These physical tricks make no new substance — proof that a mixture is only stirred together.
🎮 你来当分拣员（30 秒）🎮 Your turn: substance sorter (30 seconds)
道理讲完了，来把 4 张物质卡分进"纯净物"和"混合物"两个筐。Time to sort: drop the 4 substance cards into the pure-substance basket or the mixture basket.
一句话记住它：数一数里面藏了几种物质——只有一种的是纯净物，好几种混在一起的是混合物；混合物能用过滤、蒸发、蒸馏拆开。Remember it in one line: count the kinds inside — one kind means a pure substance, several mixed mean a mixture; mixtures can be split by filtering, evaporating or distilling.
纯净物：只有一种物质（蒸馏水、氧气、铁）Pure substance: only one kind of thing (distilled water, oxygen, iron)混合物：好几种物质混在一起（空气、盐水、果汁）Mixture: several kinds together (air, salt water, juice)分离三招：过滤拦泥沙、蒸发留盐、蒸馏收水Splitting tricks: filtering traps mud, evaporation keeps salt, distillation recovers water
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
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