Assuming that the solid being referred to is opaque, it will form a
shadow because it is not able to pass fully through it. If the light is
able to to move through the solid completely, it means that the solid is
transparent, or if only slightly through it, the solid is translucent.
You can look at magnesium, it can react with oxygen to form oxides. (chemical) it is malleable and a solid at room temperature. (physical)
to measure its density, the mass and volume can be worked out and from this density too. look up the equation, it is quite easy :)
physical changes -- it can be melted, and oxidized <span />
C. They don't have free electrons.
The only things capable of conducting a charge are things that have charged particles in them that are free to move, e.g free electrons, free positions, or dissociated ions