When a 2 kg log is burned, it produces 0.5 kg of ash. Explain why the mass of the ash is less than the mass of the log. In other words, where did all of the mass go?

my mass turned into gasses and other substances besides ash

Explanation:

burning a log products smoke and ash. the smoke takes some mass and the ash takes the rest.

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