Question

your friend suggests that measuring contact angle is an accurate way to determine how polar a substance is? based on the model above, do you agree and why?
yes, because polar substances will always bead up on any type of surface
no, because some polar molecules are hydrophobic, such as oils, so this would not work
yes, because if a polar substance is placed on a nonpolar surface, it will bead up at an angle according to its polarity
no, because contact angle is not related to polarity of a substance so it will not bead up at an angle

Explanation:

Contact angle is related to surface - liquid interactions, not directly to a substance's polarity. Polarity affects intermolecular forces within the substance, but contact angle also depends on the surface properties. For example, a polar liquid on a non - polar surface may bead up, but this is due to the mismatch in intermolecular forces (adhesive vs cohesive), not just the liquid's polarity. Also, the first option is wrong because polar substances don't always bead up (e.g., water on a clean glass surface spreads). The second option is wrong as oils are non - polar. The third option is wrong as contact angle is not solely determined by a substance's polarity.

Answer:

No, because contact angle is not related to polarity of a substance so it will not bead up at an angle.