Answer:
Everything in Earth's system can be placed into one of four major subsystems: land, water, living things, or air. These four subsystems are called "spheres." Specifically, they are the "lithosphere" (land), "hydrosphere" (water), "biosphere" (living things), and "atmosphere" (air).
Explanation:
Answer: Volume of 1g of pure gold 
Given;
Density of a pure gold=19.3 
Mass of a pure gold =1g
To find:
Volume of 1g of pure gold
Solution:
According to the formula,
Density= Mass/Volume
Where 
=density of pure gold
m=mass of pure gold
v=volume of pure gold
From the above equation volume can be calculated as
Substitute the values of mass and density value in the above equation
Result:
Thus the volume of 1g of pure gold is
The second one is more concentrated as they both times with the same thing but the second one (1.5) is bigger
<span>magnesium oxide is a compound that is composed of one atom of magnesium and two atoms of oxygen. The compound is a combination of Mg2+ ion and O2-. The ions translate into atoms which reflects on the subscripst of the elements already. magnesium oxide is a basic oxide with the pH level greater than 7.</span>
2. caco3 -> cao + co2
limestone -> calcium oxide + carbon dioxide
