Which of the following statements is true regarding the melting and boiling points of pure substances?
The boiling point is always higher than the melting point
The melting point is always higher than the boiling point
The melting and boiling points are always the same for all substances
The melting and boiling points can vary depending on the substance
Correct answer is D
The melting and boiling points are specific physical properties of each substance and can vary depending on the nature of the substance. Different substances have different melting and boiling points, which are determined by the strength of the intermolecular forces and the molecular structure of the substance.