Heat of Fusion and Vaporization
Chemistry ⇒ Thermochemistry and Energetics
Heat of Fusion and Vaporization starts at 10 and continues till grade 12.
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Describe the difference between heat of fusion and heat of vaporization.
Describe what happens to the temperature of a substance during the process of melting, assuming constant pressure.
Explain why sweating cools the body in terms of heat of vaporization.
Explain why the heat of vaporization is generally much higher than the heat of fusion for most substances.
A student heats 50 g of ice at 0°C. If the heat of fusion is 334 J/g, how much energy is needed to melt all the ice?
A 100 g sample of a substance at its melting point is cooled and releases 33,400 J as it solidifies. What is the heat of solidification, and how does it relate to the heat of fusion?
A 25 g sample of a substance at its boiling point absorbs 55,000 J of energy and vaporizes completely. Calculate the molar heat of vaporization if the molar mass of the substance is 50 g/mol.
A scientist is studying a new compound. She finds that 8.0 kJ of energy is required to melt 40.0 g of the compound at its melting point. If the compound is then heated to its boiling point and 72.0 kJ is required to vaporize the same 40.0 g, calculate the ratio of the heat of vaporization to the heat of fusion for this compound.
During which phase change is the heat of fusion involved? (1) Melting (2) Boiling (3) Condensation (4) Sublimation
Which of the following best defines the heat of fusion? (1) The energy required to change a solid to a liquid at its melting point (2) The energy required to change a liquid to a gas at its boiling point (3) The energy released when a gas condenses to a liquid (4) The energy required to raise the temperature of 1 g of a substance by 1°C
Which of the following best describes the energy change during condensation? (1) Energy is absorbed (2) Energy is released (3) No energy change (4) Energy is converted to mass
Which of the following is NOT a correct unit for heat of vaporization? (1) J/g (2) kJ/mol (3) cal/g (4) g/J
Fill in the blank: The amount of heat required to convert 1 mole of a solid into a liquid at constant temperature is called the __________ heat of fusion.
Fill in the blank: The heat of fusion is measured at the __________ point of a substance.
Fill in the blank: The process of a solid changing directly to a gas is called __________, and it requires the heat of __________.
The process of changing a liquid to a gas at its boiling point is called __________.
True or False: The heat of fusion and the heat of solidification for a substance have the same magnitude but opposite signs.
True or False: The heat of fusion is an endothermic process.
True or False: The heat of vaporization can be measured at any temperature.
True or False: The heat of vaporization is always greater than the heat of fusion for the same substance.
