Explanation:
Given that,
Mass of metal cube, m = 20 g
Volume of cube, V =5 mL
We need to find the density of the cube. Mass per unit volume equals density.
So, the density of the cube is 4 g/ml.
We know that the density of Aluminium is 4 g/mL.
So, the cube is not Aluminium cube.
A mixture can be separated. Everything in a mixture keeps it's own properties and are not chemically joined together. I am not completely sure about the compound. Although with the cake example, the ingredients have been mixed and kind of "fused" together upon baking. Hope this helps a little. (P.S. trail mix is a good example of a mixture.)
The bad smelling element is Sulfur, which smells like rotting eggs.
a)
A: Copper
B: CuO
C: 
D: $\mathrm{CuCO_3}$
E: $\mathrm{CO_2}$
F: $\mathrm{Cu(NO_3)_2}$
b)
$\mathrm{CuO+ H_2SO_4}\rightarrow \mathrm{CuSO_4 + H_2O}$
c)
$\mathrm{CuCO_3+ 2HNO_3}\rightarrow \mathrm{Cu(NO_3)_2+ CO_2+ H_2O}$
Within a physical change, an element can change forms, such as going from solid to a liquid through melting. Color change can also occur during a physical change. Physical changes are very different from chemical changes. In a chemical change the element itself changes into something else within a reaction, such as combustion (burning).
Hope this helped
