Chemistry of the Environment
IGCSE Chemistry Topic 10 10:36 English narration · English + 中文 subtitles burned in
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Look at a glass of water, and the air in this room.
看看一杯水，还有这个房间里的空气。
Both look clean and simple.
两者看起来都干净又简单。
But natural water carries dissolved oxygen, minerals, and sometimes sewage and toxic metals.
但天然水里溶有氧气、矿物质，有时还有污水和有毒金属。
And the air carries gases we put there — some of which are warming the planet.
空气里则携带着我们排放的气体——其中一些正在让地球变暖。
Chemistry tells us what is in them, how to clean them, and how to protect them.
化学告诉我们它们里面有什么、怎样净化它们、以及怎样保护它们。
This is the chemistry of the environment.
这就是环境化学。
Welcome to the chemistry of the environment.
欢迎来到环境化学。
Water, fertilisers, and air quality.
水、肥料，还有空气质量。
Let's begin.
让我们开始吧。
First, water.
首先是水。
Two colour tests show that water is present.
两个颜色测试可以显示水的存在。
Anhydrous cobalt chloride turns from blue to pink.
无水氯化钴由蓝变粉。
Anhydrous copper sulfate turns from white to blue.
无水硫酸铜由白变蓝。
But careful — those only show water is there, not that it is pure.
但要小心——这些只能说明有水，不能说明它是纯的。
To prove purity, you check the fixed points: pure water melts at exactly zero degrees, and boils at exactly one hundred.
要证明纯度，就要看固定点： 纯水恰好在零度熔化，恰好在一百度沸腾。
Any dissolved substance shifts those values.
任何溶解的物质都会改变这些数值。
Natural water is never pure: it carries dissolved oxygen, which fish need, but also sewage, toxic metals, and nitrates from fertilisers.
天然水从来不纯：它含有溶解氧，鱼需要它，但也含有污水、有毒金属，以及来自肥料的硝酸盐。
Lock this diagram in.
把这张图记住。
Two colour-change tests show water is present: cobalt chloride blue to pink, and copper sulfate white to blue.
两个颜色变化测试显示有水：氯化钴由蓝变粉，硫酸铜由白变蓝。
Only fixed melting and boiling points of zero and one hundred degrees show it is pure.
只有固定的熔点与沸点——零度和一百度——才能证明它是纯的。
That is why distilled water is used in chemistry instead of tap water — it has far fewer chemical impurities, so results are not spoiled by dissolved salts.
这就是为什么化学里用蒸馏水而不是自来水——它的化学杂质少得多，结果不会被溶解的盐干扰。
Water from rivers, lakes and the sea is never pure.
河、湖、海里的水从不纯净。
It may hold dissolved oxygen, metal compounds, plastics, sewage, harmful microbes, and nitrates and phosphates from fertilisers and detergents.
其中可能含有溶解氧、金属化合物、塑料、污水、 有害微生物，以及来自肥料和洗涤剂的硝酸盐与磷酸盐。
Some of these help: dissolved oxygen lets aquatic life breathe, and some metal compounds supply essential minerals.
有些是有益的： 溶解氧让水生生物呼吸，有些金属化合物提供必需矿物质。
Others harm: some metals are toxic, plastics hurt aquatic life, sewage carries disease-causing microbes, and nitrates and phosphates cause deoxygenation — loss of oxygen — which kills fish.
有些是有害的： 有些金属有毒，塑料伤害水生生物，污水携带致病微生物， 硝酸盐和磷酸盐造成缺氧——氧气流失——从而杀死鱼类。
So how do we make water safe to drink?
那我们怎样让水变得可以安全饮用？
Three steps.
三个步骤。
First, sedimentation and filtration — the big solid bits settle out and are filtered away.
第一，沉降和过滤—— 大块固体沉下来，然后被过滤掉。
Second, the water passes through carbon, which removes bad tastes and smells.
第二，水通过活性炭，除去异味和气味。
Third, chlorination — adding chlorine kills the harmful microbes that cause disease.
第三，氯消毒——加氯杀死引起疾病的有害微生物。
Each step removes a different problem, and the order matters: solids first, then taste, then germs.
每一步解决不同的问题， 而且顺序很重要：先除固体，再除味道，最后杀菌。
Follow the flowchart left to right.
按流程图从左到右看。
Sedimentation lets heavy solids settle.
沉降让较重的固体沉下。
Filtration traps the smaller solids that stay suspended.
过滤拦住仍悬浮的较小固体。
Carbon then strips bad tastes and smells.
然后碳除去异味和气味。
Only after that comes chlorination, which kills the microbes.
之后才是氯消毒，杀死微生物。
Skip a step, or reverse the order, and the water is not fully safe.
跳过某一步，或颠倒顺序，水就不够安全。
Next, fertilisers.
接下来是肥料。
Plants need three elements most, and fertilisers supply them.
植物最需要三种元素，肥料提供它们。
Nitrogen, for leaf and stem growth.
氮，用于叶和茎的生长。
Phosphorus, for strong roots.
磷，用于强壮的根。
And potassium, for flowers and fruit.
钾，用于开花结果。
Together they are called NPK fertilisers, after the chemical symbols.
它们合起来叫做氮磷钾肥料，取自化学符号。
Ammonium salts and nitrates are the common ones.
铵盐和硝酸盐是常见的肥料。
But there is a catch: when fertilisers wash into rivers, the nitrates cause deoxygenation, which harms fish.
但有个问题：当肥料被冲进河里，硝酸盐会造成缺氧，危害鱼类。
Three cards, one job each.
三张卡片，各有一个任务。
Nitrogen for leaf and stem growth.
氮用于叶和茎的生长。
Phosphorus for strong roots.
磷用于强壮的根。
Potassium for flowers and fruit.
钾用于开花结果。
Farmers buy NPK fertilisers to put all three into the soil at once.
农民购买氮磷钾肥料，一次把三种元素都加进土壤。
Common sources are ammonium salts and nitrates.
常见来源是铵盐和硝酸盐。
Remember the river risk: nitrates and phosphates washed off fields also drive deoxygenation in natural water.
记住河流风险：从田里冲走的硝酸盐和磷酸盐也会让天然水缺氧。
Where does the nitrogen in fertiliser come from?
肥料里的氮从哪里来？
From the air — but plants cannot use nitrogen gas directly.
来自空气——但植物不能直接利用氮气。
The Haber process solves this.
哈伯法解决了这个问题。
It combines nitrogen from the air with hydrogen to make ammonia, using a high pressure, a moderate temperature, and an iron catalyst.
它用高压、中等温度和铁催化剂，把空气中的氮和氢结合成氨。
That ammonia is then turned into ammonium salts and nitrates — the fertilisers that feed most of the world.
然后氨被转化成铵盐和硝酸盐——养活世界大部分人口的肥料。
Start with clean, dry air on the pie chart.
先看饼图上洁净干燥的空气。
About seventy-eight percent is nitrogen.
大约百分之七十八是氮。
About twenty-one percent is oxygen.
大约百分之二十一是氧。
The thin remaining slice — about one percent — is a mixture of noble gases and carbon dioxide.
剩下那薄薄的一片——大约百分之一——是稀有气体和二氧化碳的混合物。
Learn those three figures cold: exams ask them again and again.
把这三个数字记牢：考试会反复考到。
Now the air.
现在说空气。
Clean, dry air is about seventy-eight percent nitrogen, twenty-one percent oxygen, and one percent everything else — noble gases and carbon dioxide.
洁净干燥的空气大约含百分之七十八的氮、百分之二十一的氧， 还有百分之一的其他——稀有气体和二氧化碳。
But we add pollutants.
但我们加入了污染物。
Complete combustion of fuels makes carbon dioxide.
燃料完全燃烧生成二氧化碳。
Incomplete combustion makes toxic carbon monoxide, and particulates.
不完全燃烧生成有毒的一氧化碳，和颗粒物。
Car engines make oxides of nitrogen.
汽车发动机生成氮氧化物。
And burning fuels that contain sulfur makes sulfur dioxide.
燃烧含硫的燃料生成二氧化硫。
Each has an effect: carbon dioxide and methane warm the planet; carbon monoxide is poisonous; particulates cause breathing problems; and sulfur dioxide and oxides of nitrogen cause acid rain.
每一种都有影响： 二氧化碳和甲烷让地球变暖；一氧化碳有毒；颗粒物引起呼吸问题； 二氧化硫和氮氧化物造成酸雨。
Burning fossil fuels pollutes the air and changes the climate.
燃烧化石燃料污染空气并改变气候。
A power station that burns coal or oil sends out carbon dioxide, and if the fuel contains sulfur it also sends out sulfur dioxide.
燃烧煤或油的发电厂放出二氧化碳， 如果燃料含硫，还会放出二氧化硫。
Cars add oxides of nitrogen from the hot engine, and incomplete combustion on the road adds carbon monoxide and particulates.
汽车的热发动机加上氮氧化物， 路上不完全燃烧再加上一氧化碳和颗粒物。
Source first, then effect — that is how exam tables are built.
先来源，再影响——考试表格就是这样建的。
One more greenhouse gas: methane.
还有一种温室气体：甲烷。
It comes from rotting plants and from waste gases of animal digestion — farms and landfills matter as well as chimneys.
它来自腐烂的植物，以及动物消化排出的废气—— 农场和垃圾填埋场与烟囱一样重要。
Carbon dioxide and methane together drive global warming and climate change.
二氧化碳和甲烷一起推动全球变暖和气候变化。
Extra effects the table must not miss: particulates raise the risk of respiratory problems and cancer.
表格里不能漏的额外影响：颗粒物提高呼吸问题和癌症的风险。
Oxides of nitrogen also cause photochemical smog and breathing problems, not only acid rain.
氮氧化物还会造成光化学烟雾和呼吸问题，不只是酸雨。
Worked example.
例题。
A power station burns coal containing sulfur, and a lake downwind slowly turns acidic.
一座发电厂燃烧含硫的煤，下风向的湖泊慢慢变酸。
Name the pollutant, explain the link, and give one way to stop it.
说出污染物，解释联系， 并给出一种阻止办法。
Burning a fossil fuel that contains sulfur releases sulfur dioxide, which causes acid rain, so the rain falling on the lake is acidic.
燃烧含硫的化石燃料放出二氧化硫，造成酸雨， 所以落到湖上的雨是酸性的。
To stop it at the source, use flue gas desulfurisation, where calcium oxide removes sulfur dioxide from the waste gases, or switch to a low-sulfur fuel.
要在源头阻止，使用烟气脱硫，用氧化钙从废气中除去二氧化硫， 或改用低硫燃料。
A catalytic converter treats a car's oxides of nitrogen — it would do nothing about this power station's sulfur dioxide.
催化转化器处理汽车的氮氧化物——对这座发电厂的二氧化硫毫无作用。
How exactly do greenhouse gases warm the Earth?
温室气体究竟怎样让地球变暖？
Sunlight passes straight through the atmosphere and warms the ground.
阳光径直穿过大气层，温暖地面。
The warm Earth then gives off thermal energy.
温暖的地球随后放出热能。
Greenhouse gases like carbon dioxide and methane absorb some of that energy, and send it back down.
像二氧化碳和甲烷这样的温室气体吸收其中一部分能量，并把它送回地面。
Less heat escapes to space, so the Earth gets warmer.
逃逸到太空的热量减少了，所以地球变暖。
The natural opposite is photosynthesis: plants take carbon dioxide and water and, using light, make glucose and oxygen — removing carbon dioxide from the air.
自然界的反面是光合作用：植物利用光， 把二氧化碳和水变成葡萄糖和氧气——从空气中除去二氧化碳。
Trace the arrows on the diagram.
顺着图上的箭头看。
Sunlight passes through the atmosphere and warms the Earth.
阳光穿过大气层，温暖地球。
The warm ground gives off thermal energy.
温暖的地面放出热能。
Greenhouse gases absorb some of that heat and send it back down.
温室气体吸收其中一部分热并送回地面。
Less energy is lost to space, so the planet warms.
损失到太空的能量变少，所以行星变暖。
Carbon dioxide and methane are the two you must name.
你必须能说出二氧化碳和甲烷这两种。
Photosynthesis is the opposite of combustion — it removes carbon dioxide from the air instead of adding it.
光合作用是燃烧的反面——它从空气中除去二氧化碳，而不是加入。
Plants use light energy and chlorophyll to turn carbon dioxide and water into glucose and oxygen.
植物利用光能和叶绿素，把二氧化碳和水变成葡萄糖和氧气。
Say the word equation: carbon dioxide plus water goes to glucose plus oxygen.
说出文字方程式：二氧化碳加水和生成葡萄糖加氧气。
Plant more trees and you pull more carbon dioxide out of the atmosphere — one real climate fix.
多种树就能从大气中拉走更多二氧化碳——这是真正的气候对策之一。
Finally, the fixes — and each fix must match its pollutant.
最后是解决办法——而每个办法必须对应它的污染物。
To cut acid rain: fit catalytic converters in cars, which remove oxides of nitrogen; use low-sulfur fuels; and use flue gas desulfurisation, where calcium oxide strips sulfur dioxide out of a power station's waste gases.
要减少酸雨：给汽车装催化转化器， 除去氮氧化物；使用低硫燃料；使用烟气脱硫，用氧化钙把二氧化硫从发电厂的废气中除去。
To slow climate change: plant trees, burn fewer fossil fuels, and switch to renewable energy like wind and solar.
要减缓气候变化：植树、少烧化石燃料、改用风能和太阳能等可再生能源。
Careful in the exam: a catalytic converter does nothing about a power station's sulfur dioxide.
考试时要小心：催化转化器对发电厂的二氧化硫毫无作用。
Inside a catalytic converter is a ceramic honeycomb coated with catalyst metals.
催化转化器内部是涂有催化剂金属的陶瓷蜂窝。
Thousands of tiny channels give a huge surface area so the reactions run fast.
成千上万条细通道提供巨大表面积， 让反应快速进行。
In a hot car engine, nitrogen and oxygen from the air react to form oxides of nitrogen.
在热的汽车发动机里，空气中的氮和氧反应生成氮氧化物。
The converter removes them — for example carbon monoxide and nitrogen monoxide turn into carbon dioxide and nitrogen.
转化器除去它们——例如一氧化碳和一氧化氮变成二氧化碳和氮气。
It treats car exhaust, not a coal chimney.
它处理汽车尾气，不是燃煤烟囱。
Climate fixes go beyond the power station and the car.
气候对策不止发电厂和汽车。
Plant trees to take up carbon dioxide.
植树吸收二氧化碳。
Farm fewer animals to cut methane from digestion.
少养动物以减少消化产生的甲烷。
Burn fewer fossil fuels.
少烧化石燃料。
Use more hydrogen and renewable energy such as wind and solar.
多用氢能，以及风能和太阳能等可再生能源。
Each action targets greenhouse gases or the fuels that make them — match the fix to the gas, just as you matched the fix to acid rain.
每个行动都针对温室气体或产生它们的燃料——把办法和气体对应起来， 就像你把办法和酸雨对应起来一样。
Three marks to lock in.
锁住三个分。
First: the colour tests show water is present; only the fixed melting and boiling points show it is pure.
第一：颜色测试显示有水；只有固定的熔点和沸点才能证明它是纯的。
Second: match each pollutant to its source and its effect — carbon monoxide from incomplete combustion is toxic; sulfur dioxide and oxides of nitrogen cause acid rain; carbon dioxide and methane are greenhouse gases.
第二：把每种污染物与它的来源和影响对应起来——不完全燃烧产生的一氧化碳有毒； 二氧化硫和氮氧化物造成酸雨；二氧化碳和甲烷是温室气体。
Third: greenhouse gases let sunlight through but absorb the heat the Earth gives off, sending it back down.
第三：温室气体让阳光通过， 但吸收地球放出的热并送回地面。
Master these, and this topic is yours.
掌握这些，这个专题就是你的了。