Answer:
Mass of lava is 8370 g.
Step-by-step explanation:
Density: 
Density is equal to the mass of substance divided by its volume. 
Units: 
SI unit of density is Kg/m3. 
Other units are given below, 
g/cm3, g/mL , kg/L 
Formula: 
D=m/v 
D= density 
m=mass 
V=volume 
Symbol: 
The symbol used for density is called rho. It is represented by ρ. However letter D can also be used to represent the density. 
Given data: 
density of lava = 3.1 g/cm³
volume= 2700 cm³
mass= ? 
Solution:
d = m/v
m = d×v
m = 3.1 g/cm³×2700 cm³
m = 8370 g