Why are scientific theories modified and not just thrown out when new evidence is discovered? this is 8th grade science by the way

Amines are good nucleophiles, even though they are neutral molecules. how would the rate of an sn2 reaction between an amine and an alkyl halide be affected if the polarity of the solvent is increased? amines are good nucleophiles, even though they are neutral molecules. how would the rate of an reaction between an amine and an alkyl halide be affected if the polarity of the solvent is increased? because both reactants in the rate-limiting step are neutral, the reaction will be faster if the polarity of the solvent is increased. because both reactants in the rate-limiting step are neutral, the reaction will be slower if the polarity of the solvent is increased. because both reactants in the rate-limiting step are neutral, the reaction will occur at the same rate if the polarity of the solvent is increased. request answer