Answer: The law of conservation of mass is reffering to the fact that energy cannot be created or destroyed. So when you speak about atoms not being created or destroyed it is the same thing. Unless you're talking about an atomic bomb where the atoms are split.
As they get older, they become less mobile.
Answer:
It is made of atoms that are covalently bonded together.
Explanation:
For example the carbonate ion CO3++.
The carbon and oxygen atoms are held together by covalent bonds.
Answer:
Between 5.5 to 7.5
The optimum pH range for most plants is between 5.5 and 7.5