The heat of fusion for a substance is 122 joules per gram. how many joules of heat are need to melt 7.50 grams of this substance at its melting point?

915 Joules

Explanation:The heat of fusion is the heat that is required to convert a given mass of a substance from solid state to liquid state without change in temperature.In this case, we are given specific heat of a substance as 122 joules per gramIt means that amount of heat equivalent to 122 joules is required to change 1 gram of the substance from solid state to liquid state.Therefore, we can determine the amount of heat needed to change 7.5 grams of the substance from solid to liquid state.

1 g = 122 Joules

7.5 g = ?

       = 122 × 7.5

      = 915 Joules

Thus, 7.5 g of the substance at its melting point will require 915 Joules of heat to melt.