Does a woman have to cover her hands in front of non-mahram males?

Yes, a woman has to cover
her hands, because the hand is part of the ‘awrah. Al-‘Allaamah Ibn
al-Qudaamah said in al-Muqni’, as was quoted by al-Mardaawi in
al-Insaaf (1/452): The free woman is entirely ‘awrah, even her
fingernails and hair. End quote. 

Shaykh al-Islam Ibn
Taymiyah (may Allaah have mercy on him) said: It is proven in al-Saheeh
that the woman in ihraam is not allowed to wear niqaab and gloves. This is
one of the things that indicate that niqaab and gloves were customary among
women who were not in ihraam. This implies that they covered their faces and
hands. Majmoo’ al-Fataawa (15/371-372). Thus you may know that the
woman is enjoined to cover her hands in front of non-mahram men, but it does
not mean that she has to cover them with gloves. She may let part of her
garment hang down over them, and if she needs to wear gloves sometimes and
it is a little hard for her but she can put up with it, then she should put
up with it and seek reward for that, because the reward will be commensurate
with the degree of hardship involved, as it says in the hadeeth from the
Prophet (peace and blessings of Allaah be upon him). 

And Allaah knows best.