Plastic are made of one type material. why are they not classified as a composite

Zoe is investigating the composition of substance a, an unknown substance. using chemical processes, she analyzes substance a and determines it is composed of sodium, oxygen, and hydrogen atoms in a ratio of 1 : 1 : 1. what is substance a? a. a compound b. an element c. a heterogeneous mixture d. a homogeneous mixture

How many oxygen atoms are there in 3.15 moles of hcl manganese (iv) oxide, mno2

What prefix multiplier is appropriate for reporting a measurement of 5.57 ×10−5 m?