📚 Choosing Fuels | 选择燃料
Choosing a fuel is not just about finding a substance that burns. It involves comparing energy released, cost, availability, storage, safety and environmental impact. This article explains how fuels work and how we decide which fuel is best for a job.
选择燃料不只是找到一种能燃烧的物质。它涉及比较释放的能量、成本、可获得性、储存、安全性和环境影响。本文解释燃料如何起作用，以及我们如何决定哪种燃料最适合某种用途。
1. What Is a Fuel? | 什么是燃料？
A fuel is a substance that stores chemical energy and releases it as heat and light when it burns. Most everyday fuels, such as petrol, natural gas and wood, contain carbon and hydrogen.
燃料是储存化学能并在燃烧时以热和光的形式释放能量的物质。大多数日常燃料，如汽油、天然气和木材，都含有碳和氢。
Burning is a chemical reaction with oxygen. We call this combustion. Combustion converts chemical energy stored in the fuel into useful thermal energy and light energy.
燃烧是与氧气发生的化学反应，我们称之为燃烧反应。燃烧把储存在燃料中的化学能转化为有用的热能和光能。
2. The Combustion Reaction | 燃烧反应
When a fuel burns completely in plenty of oxygen, it forms carbon dioxide and water. The word equation is:
燃料在充足的氧气中完全燃烧时，会生成二氧化碳和水。文字方程式为：
fuel + oxygen → carbon dioxide + water (+ energy)
For example, methane, the main gas in natural gas, burns according to this equation:
例如，天然气的主要成分甲烷按下列方程式燃烧：
CH₄ + 2O₂ → CO₂ + 2H₂O
Complete combustion releases the maximum amount of energy and usually gives a blue flame. If the oxygen supply is limited, incomplete combustion can occur, producing carbon monoxide and soot.
完全燃烧释放最大能量，通常产生蓝色火焰。如果氧气供应不足，就会发生不完全燃烧，产生一氧化碳和碳烟。
fuel + limited oxygen → carbon monoxide + water
3. Fossil Fuels | 化石燃料
Coal, oil and natural gas are called fossil fuels. They formed from the remains of dead plants and tiny marine organisms over millions of years under heat and pressure.
煤、石油和天然气被称为化石燃料。它们由死去的植物和微小的海洋生物遗骸经过数百万年的高温高压形成。
Fossil fuels are non-renewable. They are being used much faster than they can be replaced. Once they run out, they cannot be quickly remade.
化石燃料是不可再生的。它们被使用的速度远快于其形成速度。一旦耗尽，就无法迅速再生。
They are still widely used because they are energy-rich, easy to transport and relatively inexpensive. However, burning them releases carbon dioxide and other pollutants.
它们仍被广泛使用，因为能量密度高、便于运输且成本相对低廉。但燃烧它们会释放二氧化碳和其他污染物。
4. Measuring Energy from Fuels | 测量燃料释放的能量
To compare fuels, we can burn a known mass of fuel and use the flame to heat a fixed volume of water. The temperature rise of the water gives an estimate of the energy transferred.
为了比较燃料，我们可以燃烧已知质量的燃料，用火焰加热固定体积的水。水温的升高可估算传递的能量。
A fair test must keep several variables the same: the mass of fuel, the volume of water, the starting temperature and the distance between the flame and the container.
公平实验必须保持几个变量相同：燃料质量、水的体积、起始温度以及火焰与容器之间的距离。
In the laboratory, energy is measured in joules (J) or kilojoules (kJ). A larger temperature rise usually shows that the fuel releases more energy per gram.
在实验室中，能量以焦耳（J）或千焦（kJ）为单位。温度升高越大，通常说明每克燃料释放的能量越多。
5. Factors in Choosing a Fuel | 选择燃料的因素
No single fuel is perfect for every use. We choose a fuel by comparing its energy content, physical state, boiling point, ease of storage, safety, cost and pollution.
没有一种燃料适合所有用途。我们通过比较能量含量、物理状态、沸点、储存难易、安全性、成本和污染来选择燃料。
For cars, petrol and diesel are common because they are liquid at room temperature, easy to pump and store, and release a lot of energy when burned.
汽车常用汽油和柴油，因为它们在室温下是液体，易于泵送和储存，燃烧时释放大量能量。
For home heating, natural gas is popular because it can be piped directly to buildings. Solid fuels such as coal are harder to handle but can be stored in heaps.
家庭供暖常用天然气，因为它可以直接通过管道输送到建筑物。煤等固体燃料较难处理，但可以堆放储存。
6. Environmental Impact | 环境影响
Burning fossil fuels produces carbon dioxide, a greenhouse gas linked to global warming. The more fossil fuel we burn, the more CO₂ enters the atmosphere.
燃烧化石燃料会产生二氧化碳，这是一种与全球变暖有关的温室气体。我们燃烧的化石燃料越多，进入大气的二氧化碳就越多。
Some fuels also contain sulfur. When they burn, sulfur dioxide (SO₂) is released and can dissolve in rainwater to form acid rain, which damages buildings, soil and lakes.
一些燃料还含有硫。燃烧时会释放二氧化硫（SO₂），它溶于雨水形成酸雨，损坏建筑物、土壤和湖泊。
Incomplete combustion releases carbon monoxide (CO), a toxic gas that has no colour or smell. Particulates such as soot can also cause breathing problems.
不完全燃烧会释放一氧化碳（CO），这是一种无色无味的有毒气体。烟尘等颗粒物也会引起呼吸系统问题。
7. Renewable and Alternative Fuels | 可再生燃料与替代燃料
Renewable fuels come from sources that can be replenished in a short time. Examples include wood, bioethanol and biodiesel made from plants or waste.
可再生燃料来自短期内可补充的来源。例子包括木材、用植物或废物制成的生物乙醇和生物柴油。
Biofuels are often described as carbon-neutral because the plants absorbed carbon dioxide while growing. However, energy is still needed to grow, harvest and process them.
生物燃料常被描述为碳中性，因为植物在生长过程中吸收了二氧化碳。但种植、收获和加工生物燃料仍需要能量。
Hydrogen is another alternative fuel. It produces only water when burned, so it does not release carbon dioxide at the point of use.
氢气是另一种替代燃料。它燃烧时只生成水，因此在使用时不会释放二氧化碳。
8. Hydrogen as a Fuel | 氢气作为燃料
Hydrogen can be burned in air or used in a fuel cell. In both cases, the main chemical product is water.
氢气可以在空气中燃烧或用于燃料电池。两种情况下，主要化学产物都是水。
hydrogen + oxygen → water
This makes hydrogen attractive for reducing CO₂ emissions from vehicles. However, hydrogen is a gas that is difficult to store, and it is very flammable, so it must be handled carefully.
这使得氢气在减少汽车二氧化碳排放方面很有吸引力。但氢气是一种难以储存的气体，而且非常易燃，因此必须小心处理。
Most hydrogen today is made from fossil fuels, so its overall carbon footprint depends on how it is produced. Green hydrogen, made using renewable electricity, is cleaner but more expensive.
目前大多数氢气由化石燃料制成，因此其总体碳足迹取决于生产方式。利用可再生电力制造的绿色氢气更清洁，但成本更高。
9. Comparing Fuels | 燃料比较
The table below compares some common fuels. It shows why each fuel may be chosen for a particular purpose.
下表比较了几种常见燃料。它说明了每种燃料为何会被选择用于特定用途。
| Fuel / 燃料 | State / 状态 | Main products / 主要产物 | Advantages / 优点 | Disadvantages / 缺点 |
|---|---|---|---|---|
| Coal / 煤 | Solid / 固体 | CO₂, SO₂, ash / 二氧化碳、二氧化硫、灰分 | Cheap, long-lasting / 便宜、耐烧 | Dirty, heavy / 污染大、重 |
| Petrol / 汽油 | Liquid / 液体 | CO₂, water / 二氧化碳、水 | Energy-rich, easy to store / 能量高、易储存 | Releases CO₂, flammable / 释放二氧化碳、易燃 |
| Natural gas / 天然气 | Gas / 气体 | CO₂, water / 二氧化碳、水 | Piped to homes, efficient / 可管道入户、高效 | Non-renewable, leak risk / 不可再生、有泄漏风险 |
| Hydrogen / 氢气 | Gas / 气体 | Water / 水 | No CO₂ at point of use / 使用时无二氧化碳 | Hard to store, expensive / 难储存、成本高 |
| Wood / 木材 | Solid / 固体 | CO₂, water, smoke / 二氧化碳、水、烟 | Renewable, widely available / 可再生、易获得 | Bulky, smoke pollution / 体积大、有烟污染 |
10. Making Sustainable Choices | 做出可持续的选择
Choosing a fuel wisely means balancing usefulness today with the needs of future generations. We can reduce fuel use by insulating homes, using public transport and choosing energy-efficient devices.
明智地选择燃料意味着要在今天的用途和子孙后代的需要之间取得平衡。我们可以通过房屋保温、使用公共交通和选择节能设备来减少燃料使用。
Where possible, switching to renewable electricity, biofuels or hydrogen can lower carbon dioxide emissions. However, each option still has environmental and practical costs.
在可能的情况下，改用可再生电力、生物燃料或氢气可以降低二氧化碳排放。但每种选择仍有环境和实际成本。
Scientists and engineers compare fuels over their whole life cycle: extraction, transport, use and waste disposal. This helps us choose fuels with the smallest overall impact.
科学家和工程师从燃料的整个生命周期来比较：开采、运输、使用和废物处理。这有助于选择总体影响最小的燃料。
11. Key Points Summary | 要点总结
- Fuels store chemical energy and release it by combustion. / 燃料储存化学能并通过燃烧释放。
- Complete combustion of hydrocarbons produces carbon dioxide and water. / 碳氢化合物完全燃烧生成二氧化碳和水。
- Fossil fuels are non-renewable and cause pollution, including greenhouse gases. / 化石燃料不可再生，会造成污染，包括温室气体。
- Choosing a fuel involves comparing energy, cost, storage, safety and environmental impact. / 选择燃料需要比较能量、成本、储存、安全性和环境影响。
- Renewable fuels and hydrogen can reduce emissions but have their own challenges. / 可再生燃料和氢气可以减少排放，但也有各自的挑战。
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