<p>I have some questions that I cannot understand…</p>
<p>1) Is “pure (distinct) substance” and “substance” are the same meaning, or is substance means anything different?</p>
<p>2) Do I can use unit “amu” to atomic number, mass number, and average atomic mass?</p>
<p>3) What is the difference between “Homogeneous Mixture” and “Pure Substance?” Both terms describes “uniformity throughot” but it seemed to me that both homogeneous mixture and pure substance have same composition throughout?</p>