The higher the number, the more basic the solution
pH值越高，表示溶液堿性越強(qiáng)
the lower the number, the more acidic
pH值越低，表示酸性越強(qiáng)
So our solution started off basic
我們的溶液最開始是堿性的
It was blue and had sodium hydroxide in it
它是藍(lán)色的，其中有氫氧化鈉
And this is what the chemical structure of the molecule looks like when it's blue
這是指示劑分子呈藍(lán)色時(shí)的化學(xué)結(jié)構(gòu)
The chemical bonds in the molecule are absorbing
分子中的化學(xué)鍵能夠吸收
colors of the visible spectrum that are not blue
藍(lán)色以外的可見光譜
so blue is reflected back to our eyes
所以藍(lán)色反射回我們的眼睛
Now if a compound picks up a hydrogen ion
但如果該化合物結(jié)合一個(gè)氫離子
which it would if you add an acid to it
加入酸時(shí)它確實(shí)會(huì)這樣
the molecule changes color
此時(shí)分子會(huì)變色
Now it absorbs blue and reflects yellow
它開始吸收藍(lán)光，并反射黃光
Since the colors depend on the structure of the molecule
由于顏色依賴于分子結(jié)構(gòu)
a chemist could reprogram the molecule to switch its color at
化學(xué)家可以重新構(gòu)造分子
other pHs, other numbers on this scale
讓顏色變化發(fā)生在其它pH值上
That's useful depending on the kind of reactions she may want to study
這對(duì)于所要研究的化學(xué)反應(yīng)很有用
Now nature experiments with color all the time
自然界也在不斷使用著顏色
Animals use color to avoid predators, attracts mates
動(dòng)物使用顏色來避開捕食者，吸引配偶
scare off enemies, etc
嚇退敵人，等等
Alright, so now let's take a look at
好，我們?cè)賮砜纯?/p>
what's happening in the second set of cylinders that started off pink
第二組最開始是粉色的柱形容器中發(fā)生了什么
The indicator in there is phenolphthalein
這里的指示劑是酚酞
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