Question

The density of mercury is 5,427 kg/m3. If the density of water is 1.0 g/mL, will mercury float or sink in water?

Answer 1

Mercury will sink because the destiny of mercury is 5.427 g/mL, which is greater than the 1.0g/mL density of water.

Answer 2

1 kg =1000 g = 10³ g,
1 m = 100 cm  ,
(1m)³  = (100 cm)³= (10²)³ cm³ = 10⁶ cm³  or 10⁶ mL

5,427 kg/m³ = 5,427 kg/ 1m³ = (5427 * 10³ g)/ 10⁶ mL=5427/10³ g/mL=
=5427/1000 g/mL = 5.427 g/mL 

5.427 g/mL   is density of Mercury, and 1.0 g/mL is density  of water.
Density of Mercury is more then density of the water, so
mercury will sink in the water.