十万个为什么·科学启蒙30篇（3）

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盐是从哪里来的

Most table salt comes from seawater, underground salt deposits, or ancient dried-up seas.
Seawater contains about 3.5% dissolved salts, mostly sodium chloride, left behind when water evaporates.
Salt farms—called salterns—use shallow ponds and sunshine to harvest salt naturally over weeks.
Rock salt forms when ancient oceans dried up and left thick layers buried deep underground.
Mines dig these layers out using machines, then crush and purify the salt before packaging.
Some salt also comes from brine wells, where water is pumped underground to dissolve buried salt beds.
The resulting salty water is boiled until crystals form, a method used for centuries in China and Europe.
Iodine is added to most table salt to prevent thyroid problems, especially in children.
Sea salt often retains trace minerals like magnesium and potassium, giving it a slightly different flavor.
No matter its source, salt’s chemical formula—NaCl—stays exactly the same.

听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。

No matter its source, salt’s chemical formula—NaCl—stays exactly the same. 无论来源如何，食盐的化学式——NaCl——始终完全相同。
Most table salt comes from seawater, underground salt deposits, or ancient dried-up seas. 大部分食盐来自海水、地下盐矿或远古干涸的海洋。
Salt farms—called salterns—use shallow ponds and sunshine to harvest salt naturally over weeks. 盐田（又称盐场）利用浅池和阳光，经数周自然晒制收获食盐。

这篇中文题目最接近哪一句？盐是从哪里来的一次学校运动会的通知一份超市购物清单

课文第一句的意思更接近？大部分食盐来自海水、地下盐矿或远古干涸的海洋。今天学校放假了。请把窗户打开。

这一课主要在讲什么？（看英文标题） Where Does Salt Come From? How to cook noodles A maths worksheet

No matter its source, salt’s chemical formula—NaCl—stays exactly the same.

No matter its source, salt’s chemical formula—NaCl—stays exactly the same.

第一版：录下来、回听、再听标准音。系统打分以后再加。

用今天的表达，自己说一句。

例子：No matter its source, salt’s chemical formula—NaCl—stays exactly the same.