Cambiar de ...

Question

Why is cambiar used with the preposition de and sometimes without? Is there any difference between the two ways of using cambiar?

Answer

Hola Emanuel,
We'd use "cambiar de + noun" for sentences of this type:

Cámbiate de zapatos. Esos son muy feos.
(Change shoes, those are very ugly.)
Marisa siempre está cambiando de novio.
(Marisa is always changing boyfriend.)
No he cambiado de opinión. 
(I haven't changed my mind.)

In these sentences, the whole phrase "cambiar de ..." implies that you sort of swap something for another thing of the same kind (a pair of shoes for another pair of shoes, a boyfriend for another boyfriend, an opinion for another opinion). With this short phrase we don't need to say something like:

Cámbiate esos zapatos por otros zapatos diferentes.
(Change those shoes for other different shoes.)

This could be simplified with "Cámbiate de zapatos"
Also, cambiar with no "de" is used with sentences meaning a different sort of "change" for example, change of attitude/personality in a person:

Miguel ha cambiado mucho en estos últimos años.
Miguel has changed a lot these last few years.

There is no swapping here, it is simply talking about a change in character, attitude...in a person.
Un saludo
Inma

Answer

Thank you for the informative explanation. Would I say Quiero cambiar (de) dinero? With or without the preposition. The explanation implies that the preposition de should be used...