Why do acids not show acidic behaviour in the absence of water?

When do solutions show ideal behaviour? Give two examples of ideal solution.

Why do stars twinkle?

Why do soaps not work in hard water?

Why chloroform is to be kept in a dark bottle in absence of air?

Of the two hydroxy organic compounds ROH and R'OH, the first one is basic and other is acidic in behaviour. How is R different from R'?

Explain why: Water shows unusual beheaviour among the hydrides of groups 16^(th) elements.

Why acetylene is acidic?