Why does phenolphthalein turn pink?
Phenolphthalein (HIn) is weakly acidic in nature. And in aqueous solution, it dissociates into [math]H^+[/math] and [math]In^-[/math] ions.The pink colour of the solution is due to the concentration of [math]In^-[/math] ions in the solution.Under acidic conditions, the concentration of [math]In^-[/math] in the solution is very low and concentration of [math]H^+[/math] is high, hence it is colourless.Similarly, under basic conditions, the concentration of [math]H^+[/math] ions is very low and concentration of [math]In^-[/math] is high, hence the solution is pink coloured.For example, Titration of HCl (0.1N) against NaOH (0.1N) in the presence of phenolphthalein indicator.10 ml Titrant ( HCl ) is taken in a conical flask and phenolphthalein (2–3 drops) is added to it.At this point, no Titrand (NaOH) is added to the solution.Therefore, Phenolphthalein is under acidic conditions and hence it is colourless.This solution is now titrated against Titrand ( NaOH).As soon as we add 10 ml of NaOH, complete Neutralisation takes place.HCl + NaOH ====> NaCl + [math]H_2[/math]O.At this point, Phenolphthalein indicator is under neutral conditions and it imparts very very light pink colour to the solution. This point is called as Equivalence point.Now, after the equivalence point we add 0.1 ml of NaOH.After this addition phenolphthalein comes under basic conditions and imparts Pink colour to the solution. This point is called as the End point.End point tells us that the reaction is completed.I hope, I’ve answered your query.Edit: Made answer more clear.
Which language should I learn to speak first? I can't really decide…
You have embarked on a lifetime of joy and of study. There is nothing like language study.One concerning thing is when you say that you “have tried many languages, but few interest me.” A polyglot will speak several languages (by definition) but if few languages interest you, then becoming a polyglot is decidedly much more difficult.Some polyglots will study dozens upon dozens of languages - though if you speak three or four languages you are considered a polyglot.Grammar is certainly hard, in every language. Some have a much more difficult grammar than others - Russian grammar has been described as quite difficult, and Dutch on the other hand is supposed to be very easy. (However… your experiences may be different.)Perhaps the most important thing you have stated is this:I want to learn languages so I can learn about different cultures, history, and how languages work.Thus, you should focus on languages that address these goals. Choose a culture that fascinates you, a history that you are passionate about, and select a language based on that.Your last item is very interesting - you want to learn how languages work. This opens up planned languages like Esperanto, and linguist-created languages like Klingon, Elvish, Dwarvish, and others. It sounds to me as if you would enjoy studying the linguistic work of J.R.R. Tolkein (who was a linguist - the Lord of the Rings was designed as a fictional vehicle for the languages it contains, all created by Tolkein).You might also like to study languages from different language families. Instead of studying French, Spanish, Portuguese, and Italian - all Romance - why not study French (Romance), Russian (Slavic), Greek, Japanese, and Mandarin Chinese? (Not all at once!)Also don’t rule out the more mundane reasons for learning a language - you might want to learn one because the cute gal down the street is from another country, or because the folks in your favorite bookstore all seem to speak another language, or your favorite television show (anime!) is produced originally in a different language.Good luck!