Pure substances have a ... melting and boiling point.

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Prepare for the IGCSE Edexcel Chemistry Test with engaging flashcards and multiple-choice questions. Each question comes with detailed hints and explanations to enhance your learning experience. Master your exam with confidence!

Multiple Choice

Pure substances have a ... melting and boiling point.

Explanation:
Melting and boiling points are set by the energy needed to overcome the forces holding a substance together. For a pure substance, every particle is the same, so there is a single, specific temperature at which the solid changes to a liquid and a single, specific temperature at which it boils (at a given pressure). This gives definite, fixed points. If there are impurities, the uniform structure is disturbed, so these phase changes occur over a range of temperatures rather than at one exact point. That’s why pure substances have fixed melting and boiling points.

Melting and boiling points are set by the energy needed to overcome the forces holding a substance together. For a pure substance, every particle is the same, so there is a single, specific temperature at which the solid changes to a liquid and a single, specific temperature at which it boils (at a given pressure). This gives definite, fixed points. If there are impurities, the uniform structure is disturbed, so these phase changes occur over a range of temperatures rather than at one exact point. That’s why pure substances have fixed melting and boiling points.

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