One of the uses of
estar (not
ser) is to talk about the
physical condition of something, someone or a place. This specific use of
estar is used for non-permanent conditions. Have a look and listen to these examples:
¡Vaya! Mis gafas están rotas.Oops! My glasses are broken.
Sus pantalones estaban sucios.His trousers were dirty.
¡Qué sorpresa! La habitación de mi hija está ordenada.What a surprise! My daughter's room is tidy.
Marina, estás muy guapa hoy.Marina, you look very pretty today.
Remember, this specific use of estar is used for non-permanent conditions. For permanent physical descriptions see Using ser (not estar) to express an essential or permanent characteristic
¡Vaya! Mis gafas están rotas.Oops! My glasses are broken. Marina, estás muy guapa hoy.Marina, you look very pretty today. ¡Qué sorpresa! La habitación de mi hija está ordenada.What a surprise! My daughter's room is tidy. Sus pantalones estaban sucios.His trousers were dirty. 
