The Periodic Table Song

If I had this video when I was a school girl, 

I would definitely study chemistry better.

And a slow version!

What is Quora?

Quora is a question-and-answer website and network where questions are created, answered, edited and organized by its community of users. It's a good source of knowledge. Ask any question, get real answers from people with first hand experience, and blog about what you know.

Quora's mission is 

to share and grow the world's knowledge.

What is Wordnik?

  is a very useful tool for learning new English words in the contemporary context. It is  like a dictionary, but it includes extra information, like example sentences, phrases that the word is a part of, Twitter results for each word, and statistics on the word's popularity. It's a kind of a network-based dictionary.