Hi there!
Gallium is chemical element 31, (meaning 31 protons, 31 electrons).
The symbol for Gallium is "Ga"
Hope this helps you!
~DoctorLex

Since the sound travels from the submarine to the object AND back, it actually travelled 3625x2=7250m.

Speed of sound: 1450m/s
Mass = Density * Volume
Density = 19.3 g/cm³
Volume = 24 cm³
Mass = Density * Volume = 19.3 g/cm³ * 24 cm³ = 463.2 g
Mass = 463.2 g
Is a physical change because only the state of the matter has changed.
Physical changes can often be reversed. Allowing the water to evaporate will return the salt to a solid state.
It has not combined with the water to cause an irreversible chemical reaction.