Which of these is an example of a physical change?
a banana ripening in the air
hydrogen burning in the air
zinc reacting with an acid
liquid water turning into vapor

What is the h+ concentration for an aqueous solution with poh = 4.01 at 25 ∘c? express your answer to two significant figures and include the appropriate units.

In the analysis of hair and fiber samples, which does a compound comparison microscope allow for that a conventional compound microscope does not? a. simultaneous observation b. polarization c. fluorescence d. higher magnification

Which other elements contain the same number of outer electrons as sodium