Thermal Energy and Phase Changes

The video tutorial explains the energy involved in phase changes, focusing on phase diagrams that show temperature versus heat absorbed. It covers the phase diagram for water, highlighting the constant temperature during melting and boiling. The tutorial details how to calculate heat using Q=mcΔT for temperature changes and enthalpy for phase changes. It distinguishes between endothermic and exothermic processes and provides example calculations for converting ice to steam and freezing mercury and aluminum.

What happens to the temperature of a substance during a phase change?

• It increases.

• It decreases.

• It remains constant.

• It fluctuates randomly.

Which equation is used to calculate the heat involved when the temperature of a substance changes?

• Q = mcΔT

• Q = mL

• Q = nRT

• Q = PΔV

What is the term for the heat required to change a solid to a liquid?

• Heat of vaporization

• Heat of fusion

• Heat of sublimation

• Heat of condensation

Which of the following is an endothermic phase change?

• Melting

• Deposition

• Condensation

• Freezing

What is the specific heat capacity of water in its liquid state?

• 1.996 J/g°C

• 4.18 J/g°C

• 2.09 J/g°C

• 0.5 J/g°C

How much energy is required to convert 18 grams of ice at 0°C to steam at 120°C?

• 747 kJ

• 500 kJ

• 1000 kJ

• 600 kJ

What is the heat of fusion for mercury in kilojoules per mole?

• 40.7 kJ/mol

• 10.9 kJ/mol

• 0.333 kJ/mol

• 2.3 kJ/mol

When freezing a substance, what sign does the heat of fusion take?

• Negative

• It depends on the substance

• Zero

• Positive

What is the molar mass of mercury used in the calculations?

• 300.59 g/mol

• 200.59 g/mol

• 100.59 g/mol

• 400.59 g/mol

How much energy is released when 2.5 moles of aluminum freeze at 933 K?

• 1.15 kJ

• 5.99 kJ

• 10.9 kJ

• 27.3 kJ