Define molecules escape from the surface of a liquid

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1) During evaporation, molecules escape from the surface of a liquid and enter the gas phase. This physical change requires an energy input: a molecule cannot become gaseous unless it has sufficient energy to break free of its interactions with neighboring molecules. Is evaporation an exothermic or endothermic process? (Hint: Exothermic versus endothermic processes are explained on many reliable internet sites.)

(2) Hold a small piece of ordinary ice in your hand and allow it to melt completely. Record your observations. Based on this experiment, do you think the melting process exothermic or endothermic? Explain.

(3) A 46.6-g sample of warm water was combined with a sample of liquid nitrogen in a Styrofoam cup calorimeter. The liquid nitrogen sample rapidly evaporated, leaving only cool water in the calorimeter. Careful temperature measurements showed that the water cooled from an initial temperature of 74.60C to a final temperature of 8.50C. Calculate the amount of heat released by the water. Express your answer in units of kilojoules

Reference no: EM13167812

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