Is the temperature at which a substance melts the same as the temperature changes from a liquid to a solid

No.

Explanation:

If the temperature changes a substance from it's original form, going from solid to liquid, then the temperature required to change it from a liquid to a solid are the opposite. For example, Ice is Water (H2O) in it's solid form. In order to freeze water into ice, the temperature must be very low. In order to melt the ice back into water, the temperature must be higher than the freezing point, but not too high or it will boil, making it a gaseous substance instead.

the atomic mass is the bottom number on the element.

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