Why are two sides different color on a frog

Frogs change color to help hide from predators by matching the colors of their surroundings. The also change color to help control their body temperature as some colors absorb more or less light and can cool or warm them up.

"The Dorsal surface is a green color and has spots. The Ventral surface is a lighter green color. It helps them camouflage itself from predators. The bottom of the frog is a lighter color then the top" So to camouflage themselves they adapted over time to have this certain coloring difference on their skin to adapt to their environment and survive.

if you're asking what comes out, it's steam.

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3