In physics, weight is a measure of the force exerted by gravity on a mass.
You probably know that you weigh less on the Moon than on Earth. For instance, if you weigh 100. pounds on Earth, you will weigh 16.6 pounds on the Moon. But, if your mass on Earth is 100 kg, your mass on the Moon is... also 100 kg. Because the amount of matter you have does not change from the Earth to the Moon, but the gravitational force on the Earth is stronger than on the Moon, so you weigh more on Earth.
You can think of gravity pulling a mass toward the center of an object like the Earth. It pulls a lot harder for more massive objects like the Earth than for the Moon. That's why there's a difference in weight.
As a caveat, adding energy or mass to an object will affect its mass. Additionally, general relativity informs us that when something as traveling very near the speed of light, the whole idea of mass equivalency is not exactly true...
It’s more dense than air and less dense than liquid!
Take the tiny bit of carbon dioxide and the tiny bit of water vapor out of the air,
and the rest of what you're breathing right now is a mixture of elements.
Take into account that density and relative density are given by:

Take into account that the volume associated to each of the given sustances in the table is determined by the Level Difference (because it is the change in the volume of the water of the recipient in which the substance is immersed).
The density of water in kg/m^3 is 1000 kg/m^3.
Due to the density must be given in kg/m^3, it is necessary to express the volumes of the table in m^3 and mass in kg, then, consider the following conversion factor:
1 m^3 = 1000000 ml
1 kg = 1000 g
Then, you obtain the following results:
Brass:

Cooper: