保持健康的英语作文400字【一】
苹果为什么削皮后放有一定的时间会变成褐色呢？我在书本和网络中寻找答案，得知个中原因是苹果里含有一种氧化酶，当苹果削去皮后，果肉与空气相遇，在氧化酶的催化下果肉中的氧化物质便被氧化，导致变色。
怎么样才使削皮后的苹果不变色呢？为此，我做了几个实验。
首先，把苹果果肉切成薄片，在其中的一片上滴上几滴柠檬汁，第二片涂上盐水，第三片什么都不涂。
大约10分钟过去后，第三片开始变浅咖啡色，其他两片还保持原来的鲜亮洁白。半个小时后，第三片果肉从咖啡色变成了黄褐色，其他两片仍然保持原来的颜色不变。
实验表明了柠檬水和盐水可以让去皮后的'苹果不变色。为什么柠檬汁和盐水有这个功效呢？原来柠檬汁里含有维生素C，维生素C有还原性；盐水能把空气挡在外面，果肉接触不到空气，自然不会变色了。
不管是用柠檬汁还是盐水，其原理都是阻止去皮苹果接触空气而被氧化变色，这就是保持苹果不变色的绝招！按照这样的原理，要使苹果去皮后不变色，就要想方设法阻止果肉接触空气。
为了进一步印证这个原理，我又做了第二次实验，去三片果肉片，一份暴露在空气中，一份泡在凉开水中，一份涂上橙汁，结果第一片还是在约10分钟后变色，第二份约30分钟后开始变颜色，第三片过了24小时还是没有变色。可见涂上橙汁可以防止去皮的苹果变色，原来橙汁跟柠檬汁一样含有维生素C，也能阻止苹果果肉的氧化。
因此，要想使苹果去皮后不变色，我们可以采取多种方法，只要是能够阻止空气与苹果果肉接触，都能达到目的。
保持健康的英语作文400字【二】
I attended Jack's birthday party tonight. After dinner, Jack gave cigarets to our boy students present.
At the important moment, I stop them and told them the bad effects of smoking: firstly Smoking is a waste of money and it's greatly harmful to our health. And it can lead to fires easily. So we should not smoke at all.
But it seemed helpless and they wouldn't listen to me. Somebody even said that body and health belonged to themselves and it's up to them to decide whether to smoke or not. I told him calmly, "Even if you have the right to harm your own body, but it doesn't mean that you have the same right to harm others'."
At last, they agreed with me, and some students said that they would never smoke any longer.
For the next one hour, we danced and sang happily, and nobody did smoke again.I felt very happy that my classmate all understood the harmness of smoking.
我今晚参加了杰克的生日派对。晚饭后，杰克给我们的男同学吸烟。
在重要的时刻，我阻止并告诉他们吸烟的不良影响：首先，吸烟很浪费钱，它对对我们的健康危害很大。它会很容易引起火灾。所以我们不应该吸烟，所以我们不能吸烟。
但很无奈似乎他们不听我的。甚至有人说身体是自己的，这是是否吸烟由他们自己说了算。我平静地说，“即使你有伤害自己身体的权利，但这并不意味着你要伤害别人的权利。”
最后，他们同意我的看法，一些学生说他们不会再抽烟了。
在接下来的一个小时里，我们跳舞，唱歌，没有人吸烟了。我感到非常高兴，我的同学都知道了吸烟的危害。
保持健康的英语作文400字【三】
Today smoking is a widespread habit ali over the world. Not only the old, the youth, but also middle school students have been engaged in smoking. Many of them think that smoking is a smart symbol.
However, smoking is harmful to one's health. It contributes a lot of lung cancer, from which many people have died in the past years. It can also cause many other diseases. In a word, if you smoke, you do have a much greater chance of losing your health. Furthermore, scientific research shows that smoking is not only harmful to smokers themselves, but also a threat to public health, especially to women and children. Therefore, many countries have made laws forbidding smokers to smoke m public places such as cinemas, stations, hospitals, and so on Giveup smoking! If you don't smoke, don't start. Give upsmoking for the sake of your health, for the sake of your family, and for the sake of the whole world.
当今吸烟是一个世界范围内的习惯。不仅是老人，青年，而且中学生都吸烟。他们中的许多人认为吸烟是一种潇洒的象征。
然而，吸烟有害人的健康。它会引起肺癌，其中许多人在过去的一年都死去了。它还可以造成许多其他疾病。总之，如果你吸烟，你有更大的机会失去你的健康。此外，科学研究显示，吸烟不仅对吸烟者有害，而且对公众健康构成威胁，尤其是对妇女和儿童。因此，许多国家都制定了法律禁止吸烟如电影院，车站，医院等公共场所禁止吸烟，如果你不抽烟，不要开始。戒烟吧，为了你的健康，为了你的家庭，和世界。
