📚 Making Salts – Fertilisers | 盐的制备与化肥
In KS3 chemistry, a salt is much more than the white powder you sprinkle on food. Salts are a huge family of ionic compounds made by neutralising acids. Many important fertilisers are salts, and understanding how they are made helps us link acids, bases, and agriculture.
在 KS3 化学中，盐远不止撒在食物上的白色粉末。盐是由酸被中和后生成的一大类离子化合物。许多重要的肥料都是盐，理解它们的制备方法可以帮助我们把酸、碱和农业联系起来。
1. What Is a Salt? | 什么是盐
A salt is an ionic compound formed when the hydrogen ion of an acid is replaced by a metal ion or an ammonium ion. Sodium chloride, NaCl, is only one example of a salt.
盐是酸中的氢离子被金属离子或铵根离子取代后生成的离子化合物。氯化钠（NaCl）只是盐的一个例子。
Many salts are soluble in water and can be obtained as solid crystals by evaporation. Others are insoluble and form as precipitates during reactions.
许多盐可溶于水，可以通过蒸发得到晶体。另一些盐难溶于水，在反应中以沉淀形式生成。
The name 'salt' comes from the reaction between an acid and a base, not from table salt alone.
“盐”这个名称来源于酸与碱的反应，而不仅仅指食盐。
2. Making Salts by Neutralisation | 通过中和反应制盐
When an acid reacts with a base, the products are always a salt and water. This process is called neutralisation.
酸与碱反应时，产物总是盐和水。这个过程称为中和反应。
acid + base → salt + water | 酸 + 碱 → 盐 + 水
For example, hydrochloric acid reacts with sodium hydroxide to form sodium chloride and water.
例如，盐酸与氢氧化钠反应生成氯化钠和水。
HCl + NaOH → NaCl + H₂O
The base provides the metal ion, while the acid provides the non-metal part of the salt.
碱提供金属离子，酸提供盐中的非金属部分。
3. Acid + Metal Oxide or Hydroxide | 酸 + 金属氧化物或氢氧化物
Common bases include metal oxides and metal hydroxides. Both react with acids to make salts.
常见的碱包括金属氧化物和金属氢氧化物，它们都能与酸反应生成盐。
A metal oxide is a compound of a metal and oxygen. Copper(II) oxide reacts with sulfuric acid to give copper(II) sulfate and water.
金属氧化物是金属与氧的化合物。氧化铜与硫酸反应生成硫酸铜和水。
CuO + H₂SO₄ → CuSO₄ + H₂O
A metal hydroxide contains hydroxide ions, OH⁻. Potassium hydroxide neutralises nitric acid to form potassium nitrate and water.
金属氢氧化物含有氢氧根离子 OH⁻。氢氧化钾中和硝酸生成硝酸钾和水。
KOH + HNO₃ → KNO₃ + H₂O
In the lab, an insoluble base such as copper(II) oxide is often added in excess, then filtered off before evaporating the solution to get salt crystals.
在实验室中，通常加入过量的不溶性碱（如氧化铜），然后过滤，再蒸发溶液得到盐晶体。
4. Naming Salts | 盐的命名
The name of a salt comes from the acid used and the metal or base that reacts with it.
盐的名称来源于所用的酸以及与之反应的金属或碱。
Hydrochloric acid produces chlorides, sulfuric acid produces sulfates, and nitric acid produces nitrates. Phosphoric acid produces phosphates.
盐酸生成氯化物，硫酸生成硫酸盐，硝酸生成硝酸盐，磷酸生成磷酸盐。
| Acid | 酸 | Salt ending | 盐的结尾 | Example | 例子 |
|---|---|---|
| Hydrochloric acid | 盐酸 | chloride | 氯化物 | Sodium chloride | 氯化钠 |
| Sulfuric acid | 硫酸 | sulfate | 硫酸盐 | Copper(II) sulfate | 硫酸铜 |
| Nitric acid | 硝酸 | nitrate | 硝酸盐 | Potassium nitrate | 硝酸钾 |
If a metal forms more than one ion, a Roman numeral shows the charge. For example, iron(II) sulfate contains Fe²⁺, while iron(III) sulfate contains Fe³⁺.
如果一种金属能形成不止一种离子，就用罗马数字表示电荷。例如，硫酸亚铁含 Fe²⁺，而硫酸铁含 Fe³⁺。
5. Fertilisers: Why Plants Need Salts | 肥料：植物为什么需要盐
Fertilisers are substances added to soil to provide essential chemical elements for healthy plant growth.
肥料是添加到土壤中、为植物健康生长提供必需化学元素的物质。
The three main fertiliser elements are nitrogen, phosphorus and potassium. They are often shown together as NPK.
三种主要肥料元素是氮、磷和钾，通常合称为 NPK。
Nitrogen promotes leaf growth, phosphorus supports root and flower development, and potassium improves fruit quality and disease resistance.
氮促进叶片生长，磷支持根和花的发育，钾改善果实品质和抗病能力。
Many fertiliser salts are ionic compounds containing these elements, such as ammonium nitrate, potassium chloride and superphosphate.
许多肥料盐都是含这些元素的离子化合物，例如硝酸铵、氯化钾和过磷酸钙。
6. Ammonium Salts from Ammonia | 由氨制铵盐
Ammonia is a base with the formula NH₃. It dissolves in water to form an alkaline solution.
氨是一种碱，化学式为 NH₃。它溶于水形成碱性溶液。
NH₃ + H₂O ⇌ NH₄⁺ + OH⁻
Ammonia reacts with acids to form ammonium salts, which are widely used as nitrogen fertilisers.
氨与酸反应生成铵盐，铵盐被广泛用作氮肥。
NH₃ + HNO₃ → NH₄NO₃
The ammonium ion is NH₄⁺. In ammonium nitrate, the ammonium ion is paired with the nitrate ion, NO₃⁻.
铵根离子是 NH₄⁺。在硝酸铵中，铵根离子与硝酸根离子 NO₃⁻ 配对。
Because both ions in ammonium nitrate contain nitrogen, the salt has a very high nitrogen content for plant growth.
由于硝酸铵中的两种离子都含氮，这种盐的含氮量很高，有利于植物生长。
7. Key Fertiliser Salts | 重要肥料盐
The most common nitrogen fertilisers are ammonium salts: ammonium nitrate, NH₄NO₃; ammonium sulfate, (NH₄)₂SO₄; and ammonium phosphate, (NH₄)₃PO₄.
最常见的氮肥是铵盐：硝酸铵 NH₄NO₃、硫酸铵 (NH₄)₂SO₄ 和磷酸铵 (NH₄)₃PO₄。
Potassium nitrate, KNO₃, provides both nitrogen and potassium. Potassium chloride, KCl, is a common potassium-only fertiliser.
硝酸钾 KNO₃ 同时提供氮和钾。氯化钾 KCl 是常见的纯钾肥。
Superphosphate is made by treating phosphate rock with sulfuric acid. It supplies phosphorus for root development.
过磷酸钙由磷矿石与硫酸反应制得，为根系发育提供磷。
Urea, CO(NH₂)₂, is another nitrogen-rich fertiliser, although it is not a salt. It is made industrially from ammonia and carbon dioxide.
尿素 CO(NH₂)₂ 是另一种富氮肥料，但它不是盐。工业上由氨和二氧化碳制得。
8. Making Ammonium Sulfate in the Lab | 实验室制备硫酸铵
Ammonium sulfate can be made by neutralising ammonia solution with sulfuric acid.
硫酸铵可以用氨水中和硫酸制得。
2NH₃ + H₂SO₄ → (NH₄)₂SO₄
In the lab, ammonia solution is added slowly to dilute sulfuric acid while stirring. An indicator can check when neutralisation is complete, although a pH probe is more accurate.
在实验室中，将氨水缓慢加入稀硫酸并搅拌。指示剂可以检查中和是否完成，不过 pH 探头更准确。
After neutralisation, the solution is heated gently to evaporate most of the water. White crystals of ammonium sulfate form on cooling.
中和后，将溶液轻轻加热，蒸发掉大部分水。冷却后形成白色的硫酸铵晶体。
Ammonium sulfate is safer to store than ammonium nitrate because it is less likely to decompose explosively.
硫酸铵比硝酸铵更易安全储存，因为它不太可能爆炸性分解。
9. Making Ammonium Nitrate | 制备硝酸铵
Ammonium nitrate is made by the direct reaction of ammonia with nitric acid.
硝酸铵由氨与硝酸直接反应制得。
NH₃ + HNO₃ → NH₄NO₃
The reaction is a simple neutralisation. However, the product must be kept dry and away from heat because ammonium nitrate can decompose explosively under certain conditions.
该反应是简单的中和反应。但产物必须保持干燥并远离热源，因为硝酸铵在一定条件下会爆炸性分解。
Farmers value ammonium nitrate because it contains about 35% nitrogen by mass, which is higher than many other fertilisers.
农民重视硝酸铵，因为它的含氮量按质量计约为 35%，高于许多其他肥料。
In the lab, evaporation of ammonium nitrate solution must be done very gently to avoid dangerous overheating of the solid.
在实验室中，蒸发硝酸铵溶液必须非常温和，以免固体过热发生危险。
10. Environmental Impact of Fertilisers | 肥料的环境影响
Fertilisers increase crop yields, but excessive use can damage the environment.
肥料能提高作物产量，但过量使用会破坏环境。
Rain can wash nitrate and phosphate salts from fields into rivers and lakes. This causes eutrophication: algae grow rapidly, block sunlight, and use up oxygen, which can kill fish.
雨水会把硝酸盐和磷酸盐从田地冲入河流和湖泊。这会导致富营养化：藻类迅速繁殖、遮挡阳光并消耗氧气，从而可能导致鱼类死亡。
Manufacturing fertilisers also requires energy and releases carbon dioxide, so farmers are encouraged to use the correct amount and to avoid spreading fertiliser near watercourses.
制造肥料还需要能源并释放二氧化碳，因此
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