How to identify if a natural substance is mixture or compound?

In a mixture, we can separate the elements or compounds inside easily by using physical methods, such as filtration, evaporation, distillation etc.
However, a compund is two or more elements chemically combined together, so we cannot separate them using physical methods, only with checmicals methods such as apply heat or electricity (electrolysis)

4- c, because all matter stays the same no matter what. it is still there. 5- b, because matter is known as mass. 6-c because, flammability is a chemical property. malleability is changing the shape of an object.