Which term describes a substance that melts at a lower temperature when mixed with other substances?

Which term describes a substance that melts at a lower temperature when mixed with other substances?

• A. Immiscible
• B. Hygroscopic
• C. Deliquescent
• D. Eutectic

Answer: (D)

A substance that melts at a lower temperature when mixed with other substances is describing a eutectic mixture. In a eutectic system, there is a specific ratio of components that yields the lowest melting point for that combination. At that eutectic composition, the solid phases transform to liquid at a single, lower temperature, rather than melting piece by piece at higher temperatures. This is why the mixed material melts so readily at a temperature below the melting points of the individual components—it's the special eutectic point. For example, the tin–lead solder has a eutectic composition that melts around 183°C, lower than either pure tin or pure lead. The other terms don’t describe this melting-point behavior: immiscible means components don’t mix into one phase, hygroscopic means it absorbs water from the air, and deliquescent means it dissolves into moisture it absorbs.

A substance that melts at a lower temperature when mixed with other substances is describing a eutectic mixture. In a eutectic system, there is a specific ratio of components that yields the lowest melting point for that combination. At that eutectic composition, the solid phases transform to liquid at a single, lower temperature, rather than melting piece by piece at higher temperatures. This is why the mixed material melts so readily at a temperature below the melting points of the individual components—it's the special eutectic point. For example, the tin–lead solder has a eutectic composition that melts around 183°C, lower than either pure tin or pure lead. The other terms don’t describe this melting-point behavior: immiscible means components don’t mix into one phase, hygroscopic means it absorbs water from the air, and deliquescent means it dissolves into moisture it absorbs.