Son unas chicas estupéndas ( you must add adjective ) Son chicas ( sexo feminino )

Hi! I will try to explain in english (sorry for the mistakes): When you say "chicas", you want say "girls"? Because "chicas" are the plural femmale word for "little", and "chicas" is "girls" too. I guess you are talking about "girls". "¿Son unas chicas?" sounds like a question for know more details about something. For example: For "little": Fuí a la ferretería pero no encontré las tuercas que me pediste. ¿Son unas grandes o son unas chicas?. For "girl": Las personas que vendrán a la fiesta, ¿son unas chicas?. "¿Son chicas?" is like a question with two options. For "little": ¿Las tuercas son grandes o son chicas?. No, son chicas. For "girls": ¿Tus amigos son chicos o son chicas?. Son chicas. Regards!

If you use the word "unas" you're talking about a group of women and you usually say something more about them. The other case you usually use to answer a question and you're referring women in general, not a group. For example: ¿quienes son esas chicas con el pelo rojo? Son unas chicas que cantan en este bar. ¿qué son pelirrojas? Son chicas que tienen el pelo rojo.