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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A 10 g sample of a substance at its melting point absorbs 1200 J of energy and melts completely. What is the heat of fusion?
A 100 g sample of a substance at its boiling point requires 22,600 J to vaporize completely. What is the heat of vaporization?
A 15 g sample of a substance requires 4500 J to vaporize at its boiling point. What is the heat of vaporization?
A 20 g sample of a substance requires 6800 J to vaporize at its boiling point. What is the heat of vaporization?
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?
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.
Explain why the temperature of a substance does not change during vaporization, even though heat is being added.
If 2500 J of energy is supplied to 5 g of a substance at its melting point, and the substance melts completely, what is its heat of fusion?
The heat of fusion of a substance is 150 J/g. How much energy is released when 4 g of the substance solidifies at its freezing point?
The heat of fusion of ice is 334 J/g. How much energy is required to melt 10 g of ice at 0°C?
The heat of vaporization of ethanol is 841 J/g. How much energy is released when 3 g of ethanol vapor condenses at its boiling point?
The heat of vaporization of water is approximately 2260 J/g. How much energy is needed to vaporize 2 g of water at 100°C?
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.
Describe how the values of heat of fusion and heat of vaporization for water contribute to its role in Earth's climate regulation.
Explain, at the molecular level, why the heat of vaporization is significantly higher than the heat of fusion for most substances.
