Question

The average density of the Earth from seismic observations is 5.5 g/cm^3. You've weighed a 216 in^3 (6in x 6in x 6in) cube of lherzolite (an igneous rock) using one of the trusty 115 lab scales, and determined it to weigh 25.75lb. Use this information to calculate whether the average density of the Earth can be explained by the Earth being entirely composed of lherzolite.

Answer 1

No, the average density of the earth is 5500kg/m3, which includes low density upper crustal rocks to very high-density inner core and outer core. the inner and outer core contains nickel and iron and this increases the average density of the earth. mantle material has an average density of 3300 kg/m3.

outer core density= 9900 kg/m3 inner core=12800kg/m3

Answer 2

To determine whether the average density of the Earth can be explained by the Earth being entirely composed of lherzolite, we need to calculate the density of lherzolite based on the given information and compare it to the average density of the Earth.

Given data: Average density of the Earth from seismic observations = 5.5 g/cm^3 Weight of lherzolite cube = 25.75 lb Volume of lherzolite cube = 216 in^3

First, we need to convert the weight of the lherzolite cube from pounds to grams and the volume from cubic inches to cubic centimeters to have consistent units:

1 lb ≈ 453.592 g 1 in^3 ≈ 16.3871 cm^3

Weight of lherzolite cube in grams: 25.75 lb * 453.592 g/lb ≈ 11670.79 g

Volume of lherzolite cube in cubic centimeters: 216 in^3 * 16.3871 cm^3/in^3 ≈ 3539.63 cm^3

Next, we can calculate the density of lherzolite:

Density of lherzolite = Weight / Volume Density of lherzolite = 11670.79 g / 3539.63 cm^3 ≈ 3.297 g/cm^3

Now, we compare the density of lherzolite (3.297 g/cm^3) to the average density of the Earth (5.5 g/cm^3). Since the density of lherzolite is significantly lower than the average density of the Earth, it indicates that the Earth cannot be entirely composed of lherzolite.

The average density of the Earth is much higher than the density of lherzolite, suggesting that the Earth's composition is more complex, with materials of higher density, such as iron and nickel, at its core contributing to the overall density. The Earth's core is believed to be significantly denser than the crust, which leads to the observed average density of 5.5 g/cm^3.