Which of the following statements correctly distinguishes a pure substance from a mixture?
- A) Pure substances can be separated into simpler components by physical methods, whereas mixtures require chemical reactions to separate.
- B) Pure substances have constant, characteristic melting and boiling points, whereas mixtures melt and boil over a range of temperatures.
- C) Pure substances must consist of only a single chemical element, whereas mixtures must contain multiple chemical compounds.
- D) Mixtures always display a uniform composition throughout, whereas pure substances may have a variable composition depending on the sample.
