Since the nucleophile is the actual attacking molecule or molecule that starts the reaction and allows for further steps in the mechanism to occur, it is the limiting reagent, as based on the amount of the nucleophile you have, the reaction will tend to proceed until you run out. The excess would be the sodium hydroxide, it is union part of the solution.
The dependent variable is plant height.
The <em>dependent variable</em> (plant height) is the <em>property that changes</em> as a result something the scientist does.
The <em>independent variable</em> is the <em>property that the scientist changes</em> systematically (the amount of CO_2) to see its effect.
The <em>number of plants</em> and the <em>types of plants</em> are <em>uncontrolled variables</em>. They may or may not affect the heights of the plants.
The bonding of two atoms will most likely occur if A. a more stable state can result from the union.
Otherwise, there would be no point in making two atoms bond.
It would be an physical change ; if you melt butter the butter goes from a solid to a liquid so therefore the physical state is changed.
