Pf3 has a dipole moment of 1.03 d butbf3
has a dipole moment of zero. explain thedifference.

The difference between both molecules can be explained on the basis of valance shell electron pair repulsion theory (VSEPR).  

Explanation:

The difference between both molecules can be explained on the basis of valance shell electron pair repulsion theory (VSEPR).  

PF3 which is lone pair reside on phosphorus has a tetrahedral structure and it is trigonal pyramidal. As all fluorine of molecules present on the same side, therefore, dipole doesn't cancel out hence have some dipole moment while on the other side, BF3 which is trigonal planar molecules, thus bond polarities of molecules are canceled thus giving zero net dipole moment.

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.