酸碱指示剂 化学实验系列

这是英文原版

Hi, I'm Sandy from Science World and today I'm going to show you a chemistry experiment that you can do at home. Now I've found a bunch of chemicals in my kitchen and in my bathroom and I want to know whether these things are acids or bases. How do I figure that out? What I need is an indicator, which sounds pretty fancy, but you can make an indicator out of something as ordinary as purple cabbage. I cut up a purple cabbage and added a bunch of hot water and I've got what I fondly refer to as cabbage juice. As you can see, it is this beautiful purple color. That's because it contains a pigment called anthocyanin that makes most purple and blue plants purple or blue. Anthocyanin is neat because it changes color depending on whether it's in an acid or a base. So let's take lemon juice. Acid or base. Some lemon juice into the graduated cylinder and I'll add a little bit of my cabbage juice. It turns pink. Lemon juice is an acid and in an acid, anthocyanin is going to turn red or pink. What have I got next? I've got ammonia. Now, ammonia is not something you want to play with without an adult's permission. It's pretty strong stuff. I'll put just a tiny bit into my cylinder. Now let's see what happens. Here is an acid，The cabbage juice will turn red, but here we've got something completely different happening. Our cabbage juice is turning green. That tells us that ammonia is a base. Actually, ammonia is a very strong base and bases are often used in cleaning products. The next thing I have here is soap and water. That sounds like a cleaning product. Let's see whether it's an acid or a base. Soapy water into the cylinder and we'll add the cabbage juice. Now it looks to me like this soap isn't actually changing the color of the indicator at all, which means that it's neutral. It's neither an acid nor a base. Probably healthy if you're going to put it on your skin. What else have I found here? Some vinegar. Now, you think vinegar is more like lemon juice or more like ammonia? Probably having gas. We'll put vinegar into this container and we will add some cabbage juice indicator. So what's that most like? Just like lemon juice, vinegar is in fact an acid. The last product I found is baking soda and water. If you've ever mixed baking soda and vinegar together, you know that baking soda and vinegar do something. One of the reasons you might want to know whether you have an acid or a base is to predict what kind of chemical reaction you might have. So I'm going to add some cabbage juice to the baking soda and water and we will see that that is definitely basic, sort of like the ammonia. So there we go, with simply the anthocyanin that's inside purple cabbage leaves, we are able to make an indicator that can tell the difference between acids, bases and neutral substances. Now, at Science World, we have the opportunity to use some slightly fancier indicators. In a moment, we're going to try and experiment with bromothymol blue. At Science World, we have access to special indicators like bromothymol blue. So this is an indicator that we can use to indicate an acid actually. So I'm going to put some in this giant container of water and we'll see what color it looks like. Now, despite its name, bromothymol blue actually looks clean when it's in a neutral or in a basic solution. And we want to see what it looks like in an acid. So we have to somehow make this liquid into an acid. The easiest way I know how to do that is to make it into carbonic acid by dissolving carbon dioxide in the water. And the best way I know to do that is to blow bubbles in this giant, earth-fired glass. Blow some bubbles, dissolve some carbon dioxide, make some carbonic acid, and let's see if we can make the indicator change color to indicate that we have an acid. Starting to see something happen, so that's my carbon dioxide that I'm producing, dissolving in the water, and changing the color of the indicator by turning the water into carbonic acid. That's bromethyme blue, despite its name, green in a neutral solution, and yellow in an acid like this carbonic acid solution from my breath.

这是中文翻译

嗨，我是来自科学世界的桑迪，今天我将向您展示一个可以在家中进行的化学实验。现在我在厨房和浴室找到了一些化学品，我想知道这些东西是酸还是碱。要弄清楚这一点，我需要一个指示剂，听起来很高级，但你可以用普通的紫甘蓝制作一个指示剂。我切碎了一些紫甘蓝，加了一些热水，得到了我们称之为紫甘蓝汁的东西。正如您所看到的，它是一种美丽的紫色。这是因为它含有一种叫做花色素的色素，使大多数紫色和蓝色的植物呈现紫色或蓝色。花色素很神奇，因为它会根据所处的酸性或碱性而改变颜色。现在我们来看看柠檬汁。酸性还是碱性？我将一些柠檬汁倒入量筒中，然后加入一点紫甘蓝汁。它变成了粉红色。柠檬汁是一种酸，在酸性环境中，花色素会变成红色或粉红色。接下来是氨水。现在，氨水不是您没有成年人许可就可以玩的东西。它是相当强力的物质。我只加入了一点点到量筒中。现在我们来看看会发生什么。这里是一个酸，紫甘蓝汁会变红，但这里发生了完全不同的反应。我们的紫甘蓝汁变成了绿色。这告诉我们氨水是一种碱。实际上，氨水是一种非常强的碱，碱经常用于清洁产品中。下一个是肥皂和水。听起来像是清洁产品。我们来看看它是酸还是碱。将肥皂水倒入量筒中，然后加入紫甘蓝汁。现在看起来好像这个肥皂实际上没有改变指示剂的颜色，这意味着它是中性的，既不是酸也不是碱。如果你要把它涂在皮肤上，这可能是健康的。我还找到了一些醋。你认为醋更像柠檬汁还是氨水？可能会产生反应。我们将醋倒入容器中，然后加入一些紫甘蓝汁指示剂。那个结果最像什么？就像柠檬汁一样，醋实际上是酸性的。我找到的最后一个产品是小苏打和水。如果你曾经将小苏打和醋混合在一起，你就会知道小苏打和醋会发生反应。了解您是否有酸性或碱性物质的一个原因是为了预测可能发生的化学反应类型。因此，我将在小苏打和水中加入一些紫甘蓝汁，我们将看到它肯定是碱性的，有点像氨水。这样一来，我们只需使用紫甘蓝叶中的花色素，就能制作出一个可以区分酸、碱和中性物质的指示剂。在科学世界，我们有机会使用一些稍微高级的指示剂。接下来，我们将尝试使用溴甲蓝进行实验。在科学世界，我们可以使用溴甲蓝等特殊指示剂。实际上，这是一种可以用来指示酸性的指示剂。我将一些溴甲蓝放入这个巨大的水容器中，我们将看到它的颜色是什么样子的。尽管它的名字是溴甲蓝，但在中性或碱性溶液中它实际上看起来是干净的。我们想要看看它在酸性溶液中的表现。所以我们必须以某种方式使这种液体成为酸性的。我知道最简单的方法是将它转化为碳酸。通过将二氧化碳溶解在水中。而我所知道的最好的方法是在这个巨大的陶瓷玻璃中吹泡泡。吹一些泡泡，溶解一些二氧化碳，生成一些碳酸，让我们看看是否能让指示剂改变颜色，表明我们有一个酸性溶液。开始看到一些变化，那是我产生的二氧化碳溶解在水中，通过将水转化为碳酸，改变了指示剂的颜色。这就是溴甲蓝，在中性溶液中是绿色的，而在酸性溶液中（比如我呼出的碳酸溶液）是黄色的。