120 pounds of dry concrete mix is a significant amount of material, totaling 120 lb (54.4 kg). It is about the size of a 5-gallon bucket and occupies a volume of 7.19 gal (27.2 L).

Volume
7.19 gallons
7.19 gal (27.2 L)
about the size of a 5-gallon bucket
Dry concrete mix typically ranges 1.9–2.2 g/mL depending on how it's packed. A firmly packed scoop weighs more.