The amount of heat required to melt lead at it melting temperature is 23.0 kj/kg. the amount of heat required to melt mercury at its melting temperature is 11.4 kj/kg. what is the effect of adding 24 kj of thermal energy to 1 kg of mercury and lead when each have just reached their melting temperatures? the addition of 24 kj of energy will allow all of the mercury and lead to change from solid to liquid. the temperature of each substance will also increase. the addition of 24 kj of energy will allow all of the mercury and lead to change from solid to liquid. the temperature of each substance will not change. the addition of 24 kj of energy will allow all of the mercury to change from solid to liquid, and some of the lead to change from solid to liquid. only the temperature of the mercury will increase. the addition of 24 kj of energy will allow all of the mercury and lead to change from liquid to gas. the temperature of each substance will increase.