Arrange them according to their melting pointH2O PH3 SiO2.NH3  

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megamind-616 eNotes educator| Certified Educator

Melting point is the temperature at which a substance turns from solid to liquid (melts). Melting point is considered to be a physical property of a substance. Physical properties are measurable properties that allude to a substance's characteristics or state. Other examples of physical properties are density, solubility, atomic mass, and boiling point. 

Below are the compounds listed within the question arranged from low to high melting points. All temperatures are in degrees Celcius. 

PH3 (phosphine) = -132.8

NH3 (ammonia) = -77.73

H2O (water) = 0

SiO2 (silicon dioxide) = 1600

Melting point is in contrast to chemical properties, which describe the reactivity of a substance. For example, flammable and corrosive are words to describe chemical properties.

The chemteam.info describes chemical versus physical properties in more detail and gives additional examples of each.