Heat Transfer and Thermodynamics Review

30 question-and-answer style flashcards covering the key concepts of heat transfer, thermal conduction, convection, radiation, planetary energy balance, and phase changes drawn from the lecture notes.

What are the three fundamental methods of heat transfer?

Conduction, convection, and radiation.

Which sub-atomic particles are chiefly responsible for thermal conduction in metals?

Mobile electrons.

Does "cold" flow from ice to your hand when you touch a metal bar whose other end rests on ice?

No. Heat flows from your hand to the ice; "cold" is the absence of heat flow.

Why can a firewalker step barefoot on glowing wooden coals without injury?

Wood is a poor thermal conductor, so little heat is transferred to the foot during brief contact.

Thermal convection operates mainly in which type of materials?

Fluids (liquids and gases).

What temperature change occurs when air rapidly expands?

It cools (adiabatic expansion).

Which bodies emit radiant energy into space?

Both the Sun and the Earth emit radiant energy.

What is the primary origin of Earth’s internal thermal energy?

Radioactive decay of elements within Earth’s interior.

If an object absorbs radiant energy well, how does it typically behave as an emitter?

It also emits radiant energy well.

A hot pizza placed in the snow is primarily a net .

Emitter of radiant energy (loses more than it gains).

In terms of cause and effect, which statement is more accurate: "A black object absorbs energy well" or "An object that absorbs energy well appears black"?

"An object that absorbs energy well appears black" is more accurate (absorption leads to black appearance).

Will wrapping a fur coat around a thermometer normally change its reading?

No. The coat is an insulator, not a heat source; both reach the same temperature.

Why are mountaintops often snow-covered while valleys below are warmer and green?

Rising warm air cools with expansion, and valleys are blanketed by thicker, insulating air layers.

If a good absorber of radiation were a poor emitter, how would its temperature compare to its surroundings?

It would be higher, because it would gain more energy than it loses.

What would happen to Earth’s average temperature if the atmosphere became more transparent to infrared radiation?

Earth would cool (reduced greenhouse effect).

When a liquid vaporizes into a gas, does it absorb or release energy?

It absorbs energy (latent heat of vaporization).

During boiling, why does the temperature of the liquid remain nearly constant?

Added energy goes into changing phase (breaking intermolecular bonds) rather than raising temperature.

In the crushed-can demonstration, what primarily lowers the internal gas pressure when the can is inverted into water?

Condensation of steam inside the can, which reduces the amount of gas and its pressure.

When a dish of water sits open to the air, what processes occur at the surface?

Both evaporation and condensation occur simultaneously; the net rate determines water level.

Why can briefly touching a hot iron with a wet finger prevent a burn?

The water on the finger absorbs heat as it vaporizes, protecting the skin (Leidenfrost effect).

For kitchen use, would a salt that raises or lowers water’s boiling point be more useful?

One that raises the boiling point; it allows cooking at a higher temperature, shortening cooking times.

In which direction does heat naturally flow?

From higher-temperature objects to lower-temperature objects.

What term describes the cooling of air as it rises and expands in the atmosphere?

Adiabatic cooling.

Why is a good absorber also a good emitter according to Kirchhoff’s law of thermal radiation?

At a given temperature and wavelength, absorptivity equals emissivity; materials that absorb well must radiate equally well.

If the same bowl of hot chili is placed in a hotter oven, is it a net emitter or absorber?

Net absorber; it gains more radiant energy than it loses.

How does poor thermal conductivity help during firewalking?

It limits the rate at which heat transfers to the foot, preventing burns.

What effect does adding energy to a substance undergoing a phase change have on its temperature?

Generally none; the energy goes into changing phase rather than increasing temperature.

Why do valleys stay warmer at night compared to surrounding high terrain?

A thicker blanket of air acts as insulation, trapping heat near the surface.

What physical law explains why increasing greenhouse gases warm Earth?

They lower atmospheric transparency to infrared radiation, trapping outgoing heat (greenhouse effect).

Why does the pressure inside a sealed container of gas rise when it is heated?

Gas molecules move faster, collide more frequently and forcefully with the container walls, increasing pressure (Gay-Lussac’s law).