The aggregate state of a substance depends on its melting point (if it was originally a solid), boiling point and triple point.
Oxygen has a temperature of -215 °. This means that he passed the temperature of the triple point (it is equal to -219 °). At the temperature of the triple point, the substance is in two phases at once. Therefore, the state of oxygen is gas and liquid. Mercury melts at a temperature of -38.9 °. This means that mercury is in a solid state. Copper melts at a temperature of 1084 ° C, which means that copper is a liquid.
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