Thermodynamics and Phase Changes

Dr. English introduces intermolecular forces, focusing on phase diagrams and enthalpy changes. The tutorial covers phase changes, heating curves, and calculating enthalpy changes using specific formulas. A detailed example demonstrates how to calculate the enthalpy change for converting water to steam, emphasizing the importance of understanding phase diagrams and energy calculations.

What is the term used for the phase change from solid to gas?

• Sublimation

• Fusion

• Condensation

• Vaporization

Which phase change involves energy being released?

• Melting

• Sublimation

• Vaporization

• Freezing

During a phase change, what happens to the temperature of the substance?

• It decreases

• It remains constant

• It fluctuates

• It increases

What is the key concept of Hess's Law in relation to enthalpy changes?

• Enthalpy changes are independent of the path taken

• Enthalpy changes are always negative

• Enthalpy changes depend on the path taken

• Enthalpy changes are always positive

Which formula is used to calculate the energy change when there is a change in temperature?

• q = mgh

• q = mcΔT

• q = ΔH fusion

• q = ΔH vaporization

What is the specific heat capacity of water as a liquid?

• 1.84 J/g°C

• 4.18 J/g°C

• 2.09 J/g°C

• 3.98 J/g°C

In the example, what is the first step in calculating the enthalpy change for converting water to steam?

• Draw the phase diagram

• Convert grams to moles

• Calculate the heat of vaporization

• Calculate the heat of fusion

What is the heat of vaporization of water used in the example?

• 44.0 kJ/mol

• 40.7 kJ/mol

• 50.2 kJ/mol

• 36.5 kJ/mol

How many moles of water are equivalent to 45 grams?

• 2.0 moles

• 3.0 moles

• 2.5 moles

• 1.5 moles

What is the final enthalpy change calculated in the example?

• 110.5 kJ

• 124.2 kJ

• 101.75 kJ

• 117.1 kJ