The speed of sound depends on the density of the medium in which it is travelling and increases when the density increases. For example, in solids sound travels faster than in liquid and even faster than in gas, and the density is highest in solids, lower in liquids and lowest in gas.

So iron has a density of about 7,800 kg/m$^3$, while mercury has 13,600 kg/m$^3$, but the speed of sound is 1,450 m/s in mercury and 5,130 m/s in iron, so mercury has a higher density, but sound travels slower in it. Why is this?

The speed of sound depends on the density of the medium in which it is travelling and increases when the density increases. For example, in solids sound travels faster than in liquid and even faster than in gas, and the density is highest in solids, lower in liquids and lowest in gas.

So iron has a density of about $7\,800\ \mathrm{kg/m^3}$, while mercury has $13\,600\ \mathrm{kg/m^3}$, but the speed of sound is $1\,450\ \mathrm{kg/m^3}$ in mercury and $5\,130\ \mathrm{kg/m^3}$ in iron, so mercury has a higher density, but sound travels slower in it. Why is this?

The speed of sound depends on the density of the medium in which it is travelling and increases when the density increases. For example, in solids sound travels faster than in liquid and even more than in gas and the density is highest in solids, lower in liquids and lowest in gas.

So iron has a density of about 7,800 kg/m^3 while mercury has 13,600 kg/m^3, but the speed of sound is 1,450 m/s in mercury and 5,130 m/s in iron, so mercury has a higher density, but sound travels slower in it. Why is it?

The speed of sound depends on the density of the medium in which it is travelling and increases when the density increases. For example, in solids sound travels faster than in liquid and even faster than in gas, and the density is highest in solids, lower in liquids and lowest in gas.

So iron has a density of about 7,800 kg/m$^3$, while mercury has 13,600 kg/m$^3$, but the speed of sound is 1,450 m/s in mercury and 5,130 m/s in iron, so mercury has a higher density, but sound travels slower in it. Why is this?

Sound depends on density and increases when density increases. for example in solids sound travels faster than in liquid and even more than in gas and the density is highest in solids, lower in liquids and lowest in gas. So iron has density of about 7800 while mercury has 13600 but speed of sound is 1450 in mercury and 5130 in iron so mercury has more density but sound travels slower in it. Why is it?

The speed of sound depends on the density of the medium in which it is travelling and increases when the density increases. For example, in solids sound travels faster than in liquid and even more than in gas and the density is highest in solids, lower in liquids and lowest in gas. 

So iron has a density of about 7,800 kg/m^3 while mercury has 13,600 kg/m^3, but the speed of sound is 1,450 m/s in mercury and 5,130 m/s in iron, so mercury has a higher density, but sound travels slower in it. Why is it?