Your teacher gives you a black powder. When you dissolve the powder in water, you see red particles that float on top, black particles that sink to the bottom, and a green liquid. Was the black powder a pure substance, mixture, element, or compound?
Mixture
A molecule of ozone gas has three atoms of oxygen. Which of these describes ozone most specifically?
Element
The chemical formula for sodium citrate is Na 3C 6H 5O 7. Which of the following statements is true?
Sodium citrate is a compound with a total of 21 atoms.
