What are the significance of metals in human life and civilization? can someone help me answer this?​

Metals have an important role in our daily life. The discovery of the metal is said to be the most important milestone in the history of human civilization. We cannot live without machines now. All machines are made up of metals. Machines reduce the work of man. Many modern facilities would not have been possible without metals. Most metals occur as their compounds in nature.

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.