13 A2 water vital for life

CHAPTER 1 Water in Our Lives PEOPLE USE A LOT OF WATER EVERY DAY. HOW MUCH DO YOU USE? A person can live without food for more than a month. Without water, a person dies in less than one week. We need water inside our bodies. We need water outside our bodies, too. We need to wash our clothes, our dishes, our food, and our bodies. A person can easily use seven and a half liters of water a day to brush his teeth. We also need water to make food. It takes three and a half liters of water to process the meat for one hamburger.

第一章我们生活中的水人们每天使用大量的水。 你用多少？一个人不吃东西可以活一个多月。 没有水，一个人不到一周就会死亡。 我们体内需要水。 我们也需要体外的水。 我们需要洗衣服、洗盘子、洗食物、洗身体。 一个人每天可以轻松地使用7.5升水来刷牙。 我们也需要水来制作食物。 加工一个汉堡的肉需要3.5升水。

We even need water for the cars we drive. It takes 7,843 liters of water to make four new tires for a car. Not everyone uses the same amount of water, however. The average person in the United States uses 2,500,000 liters every year. That's the same as an Olympic swimming pool! Someone in China uses about 700,000 liters in a year. People in Uganda or Ethiopia use about 5,000. One reason for this big difference is the way people use water. Do you leave the water running when you brush your teeth? That's about 11 liters per minute. Do you take a shower or a bath? A five-minute shower uses about 75 liters of water. A full bathtub can hold 130 liters. Do you wash your car in the sunshine, or do you wait until it rains?

我们甚至需要水来开汽车。 为一辆汽车制造四个新轮胎需要7843升水。 然而，并不是每个人都用同样的水量。 美国人平均每年使用250万升。 这和奥林匹克游泳池是一样的！在中国，有人一年要用掉大约70万升。 乌干达和埃塞俄比亚的人使用大约5000种。 造成这种巨大差异的一个原因是人们使用水的方式。 你刷牙的时候让水开着吗？ 也就是每分钟11升。 你洗澡还是泡澡？ 5分钟的淋浴要用75升水。 一个装满水的浴缸可以装130升水。 你是在阳光下洗车，还是等到下雨？

CHAPTER 2 Water in the Air SOMETIMES WE CAN SEE WATER IN THE AIR- AND SOMETIMES WE CANT: There is a lot of water in the air. Think of clouds, for example. A cloud is a group of very small drops of water. The drops are so small that they float in the air. There are different kinds of clouds. Cumulus clouds are big and fluffy. Cirrus clouds are very thin and long. When cirrus clouds are in the sky, it means the weather is going to change soon. Cumulus and cirrus clouds are white. They are white because the drops of water are not very close together. Gray clouds have more water, and the drops are very close together. These are rain clouds, or nimbostratus clouds.

第二章空气中的水有时我们能看到空气中的水——有时我们看不见：空气中有很多水。 以云为例。 云是一组非常小的水滴。 水滴很小，可以漂浮在空中。 有不同种类的云。 积云又大又蓬松。 卷云很薄很长。 当天空中出现卷云时，就意味着天气即将发生变化。 积云和卷云是白色的。 它们是白色的，因为水滴不是靠得很近。 灰色的云里有更多的水，水滴也靠得很近。 这些是雨云，或称雨层云。

Fog is also a cloud. But it is not up in the sky. It is down on the ground where we walk. Fog can be beautiful, but it can also be scary. Fog stops you from seeing or hearing things well, so most people don't feel safe when it's very foggy. That's why there is often a lot of fog in scary movies. London is famous for its fog. In old movies with detectives like Sherlock Holmes, the streets of London are often full of fog. But that wasn't really fog. It was smog! When fog mixes with smoke in the air, it makes smog. Smog isn't healthy for people to breathe. Today, there isn't as much smog in London as there was in the days of Sherlock Holmes. The air is much cleaner, but it's still often foggy in London.

雾也是一种云。但它不是在天上。 它就在我们行走的地方。 雾可以是美丽的，但它也可以是可怕的。 雾会让你看不清或听不清东西，所以大多数人在雾很大的时候会感到不安全。 这就是为什么恐怖电影中经常有很多雾的原因。 伦敦以雾而闻名。 在像夏洛克·福尔摩斯这样的侦探的老电影中，伦敦的街道经常充满了雾。 但那不是真正的雾。 是雾霾！当雾与空气中的烟混合时，就形成了烟雾。 人们呼吸烟雾是不健康的。 如今，伦敦的雾霾已经没有福尔摩斯时代那么严重了。 伦敦的空气干净多了，但仍然经常有雾。

Humidity means how much water is in the air. On a humid summer day, the skin on your arms, face, and legs feels wet. It's hard to breathe because the air feels heavy. Your clothes stick to your body, and you feel uncomfortable. When the weather is humid, the temperature usually feels higher than it really is. Think about this: when the air temperature is 24C and there is 0 percent humidity, it feels like 21C to our bodies. But if the humidity is 100 percent, it feels like 27C. That's why you feel more comfortable in a warm, dry place than in a warm, humid place.

湿度意味着空气中有多少水。 在潮湿的夏天，你的手臂、脸和腿上的皮肤感觉湿润。 呼吸困难，因为空气感觉很重。 你的衣服粘在身上，你感到不舒服。 当天气潮湿时，温度通常感觉比实际温度高。 想想看：当气温为24摄氏度，湿度为0%时，我们的身体感觉就像21摄氏度。 但如果湿度是100%，感觉就像27摄氏度。 这就是为什么你觉得在温暖干燥的地方比在温暖潮湿的地方更舒服。

Of course, water can also be in the air in the form of rain. When the tiny drops of water in the air come together, they get big and heavy and make clouds. When the drops become too heavy, they fall from the clouds as rain. If it rains too much rain in one place, then a flood can happen. The water from rivers goes onto fields, into towns, and into buildings. But there are good floods and bad floods. Good floods can help farmers. The flood waters can bring new richer soil into the fields. That means it's easier for the farmers to grow crops. Bad floods can kill people and destroy homes. In October 2011, there was a very bad flood in Thailand. As many as 800 people died, and tens of thousands of people lost their homes.

当然，水也可以以雨的形式存在于空气中。 当空气中的小水滴聚集在一起时，它们变得又大又重，形成了云。 当水滴变得太重时，它们就会以雨的形式从云层中落下。 如果一个地方下了太多的雨，就会发生洪水。 河水流入农田，流入城镇，流入建筑物。 但是有好的洪水和坏的洪水。 好的洪水可以帮助农民。 洪水会给田地带来新的更肥沃的土壤。 这意味着农民更容易种植庄稼。 严重的洪水可以杀死人，摧毁房屋。 2011年10月，泰国发生了一场非常严重的洪水。 多达800人死亡，数万人失去家园。