Determine a massa, em kg, de um material que está contida em um volume de 18l. sabe-se que a densidade do material é de 0,9 g/cm3

The question in English is "Determine the mass, in kg, of a material that is contained in a volume of 18L. It is known that the material density is 0.9 g/cm 3"

 

We can use a simple equation to solve this problem. 
    d = m/v

Where d is the density, m is the mass and v is the volume.

d = 0.9 g/cm³
m = ?
v = 18 L = 18 x 10³ cm³

By applying the equation,
    0.9 g/cm³ = m / 18 x 10³ cm³
                  m = 0.9 g/cm³ x 18 x 10³ cm³ 
                  m = 16200 g
                  m = 16.2 kg

Hence, the mass of 18 L of material is 16.2 kg.

Vander waals forces are inter molecular bonds that exist within molecules of the same substance. a water molecule is made up of oxygen and hydrogen atoms which share electrons between each other. the vander waals forces are forces that exist between multitude of different  molecules of water. dipole dipole forces is the type of vander waals force that exist in water. the oxygen atom which is more electronegative pulls the shared electron closer to itself thus generating a partial negative charge while the hydrogen acquire a partial positive charge. these two different charges causes attraction to occur in water molecules.

Gamma waves is the answer