Question 1

Which process is illustrated by the image of dry ice (solid CO2) disappearing without leaving any liquid behind?

Accepted Answer

Sublimation

Question 2

A kettle is boiling water at sea level. What is the main difference between boiling and evaporation?

Accepted Answer

Boiling occurs only at the boiling point and throughout the volume, while evaporation occurs at any temperature below boiling and only at the surface.

Question 3

What happens to the temperature of ice at 0°C when heat is added until all the ice melts?

Accepted Answer

The temperature remains constant until all the ice melts.

Question 4

Which equation correctly represents the heat required for a phase change?

Accepted Answer

$$Q = \pm mL$$

Question 5

If 1 kg of water at 100°C is converted to steam at 100°C, how much energy is required? (Latent heat of vaporization for water $$L_v = 2.256 	imes 10^6$ J/kg)

Accepted Answer

$$Q = 2.256 	imes 10^6$ J

Question 6

Why does water boil at a lower temperature on top of Mount Everest compared to sea level?

Accepted Answer

Because the atmospheric pressure is lower at higher altitudes.

Question 7

A metal (gallium) melts in your hand at room temperature. If its latent heat of fusion is $$L_f = 8.04 	imes 10^4$ J/kg, which statement is correct?

Accepted Answer

Gallium requires less energy per kg to melt than ice.

Question 8

Which phase change occurs when heat is removed from water vapor at 100°C at atmospheric pressure?

Accepted Answer

Condensation

Question 9

A student heats a mixture of ice and water at 0°C. Which formula should they use to calculate the heat required to melt all the ice?

Accepted Answer

$$Q = mL_f$$

Question 10

Which of the following best describes the latent heat?

Accepted Answer

The heat required to change the phase of a unit mass of a substance without changing its temperature.

Question 11

If 1 kg of water is heated from 0°C to 100°C, how much energy is required? (Specific heat of water $$c = 4190 J/kg$$·K)

Accepted Answer

$$Q = 4.19 	imes 10^5$ J

Question 12

Which phase change is responsible for the 'disappearing teaspoon' phenomenon when gallium melts in your hand?

Accepted Answer

Melting (fusion)

Question 13

Which statement about phase changes is correct?

Accepted Answer

Phase changes occur at a definite temperature for a given pressure.

Question 14

A beaker contains ice and water at 0°C. If heat is added, what happens first?

Accepted Answer

The ice melts without a change in temperature.

Question 15

Which phase change requires the greatest amount of energy for water per kilogram?

Accepted Answer

Vaporization

Question 16

Which real-life scenario best illustrates evaporation?

Accepted Answer

Feeling cold after stepping out of a swimming pool as water evaporates from your skin.

Question 17

Which phase change occurs when heat is supplied to a solid at its melting point?

Accepted Answer

Melting (fusion)

Question 18

Which factor determines the boiling point of a liquid?

Accepted Answer

Both temperature and pressure

Question 19

Which phase change is represented by the equation $$Q = mL_v$$?

Accepted Answer

Vaporization (boiling)

Question 20

A student observes that dry ice (solid CO2) disappears without forming a liquid. What is the most likely explanation?

Accepted Answer

CO2 sublimates because it cannot exist as a liquid at atmospheric pressure.

Heat and Phase Changes: Physics Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards