The ratio of the mass of a substance to its volume is called

I believe it is called, Density.

Answer : The ratio of the mass of a substance to its volume is called density.

Explanation :

Density : It is defined as the mass of a substance contained per unit volume.

The unit of mass is gram (g) and the unit of volume is milliliter (ml). So, the unit of density is g/ml.

Formula used :

For example : If mass of object is 550 grams  and volume of water displaced 25 ml. Calculate the density of an object.

By using formula, we get:

Thus, density of the object will be 22 g/ml