今天带大家来了解一下Elephant’s Toothpaste ：大象牙膏实验。
大象牙膏实验的原理是由于使用碘化钾(potassium iodide)或者酵母(Yeast)等物质作为催化剂(catalyst)，加速了双氧水(hydrogen peroxide)分解速率，分解出大量氧气，因为分解速率快，，所以产生了大量的泡泡。这个反应速率取决于双氧水的浓度，我们在视频中能看到，随着浓度的增加，反应速度越来越快。同时，除了肉眼可见的”泡沫山”(volcano of foam)，这个反应还产生了热，所以也叫做放热反应(Exothermic Reaction)
What to do?
1. Use a funnel to carefully pour 1/2 cup (118 ml) of the hydrogen peroxide liquid into the bottle
2. Add about 10 drops of your favorite food coloring into the bottle.
3. Add about 1 tablespoon (15ml) of liquid dish soap into the bottle and swish the bottle around a bit to mix it.
4. In a separate small cup, combine the warm water and the yeast together and mix for about 30 seconds. It should be about the consistency of melted ice cream – add a bit more warm water if needed.
5. Now the adventure starts! Use the funnel to pour the yeast-water mixture into the bottle and watch the foaminess begin!
How does it work?
Foam is awesome! The foam you made is extra-special because each tiny foam bubble is filled with oxygen.The yeast acted as a catalyst; a catalyst is used to speed up a reaction. It quickly broke apart the oxygen from the hydrogen peroxide. Because it did this very fast, it created lots and lots of bubbles. Did you notice the bottle got warm. Your experiment created a reaction called an Exothermic Reaction – that means it not only created foam, it created heat! The foam produced is just water, soap, and oxygen so you can clean it up
with a sponge and pour any extra liquid left in the bottle down the drain.
This experiment is sometimes called “Elephant’s Toothpaste” because it looks like toothpaste coming out of a tube, but don’t get the foam in your mouth!
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