Question

Which of the following choices correctly identifies the following three heat transfer processes? Heat transferred from the Sun to the Earth A metal spoon heating up when placed in a pot of hot soup A rising plume of smoke from a fire a. I. Radiation; II. Conduction; III. Convection b. I. Conduction; II. Radiation; III. Convection c. I. Radiation; II. Convection; III. Conduction d. I. Convection; II. Conduction; III. Radiation

Short answer

a. I. Radiation; II. Conduction; III. Convection

Step-by-step solution

Understand Heat Transfer Processes

There are three main types of heat transfer: Radiation, Conduction, and Convection. Radiation is the transfer of heat through electromagnetic waves without needing a medium. Conduction is the transfer of heat through direct contact between materials. Convection is the transfer of heat by the movement of fluid (liquid or gas).

Analyze Heat Transfer – Sun to Earth

Heat transferred from the Sun to the Earth occurs through space, where there is no medium. This type of heat transfer is Radiation.

Analyze Heat Transfer – Metal Spoon in Hot Soup

A metal spoon heating up when placed in a pot of hot soup involves direct contact between the spoon and the hot soup. This type of heat transfer is Conduction.

Analyze Heat Transfer – Rising Plume of Smoke

A rising plume of smoke from a fire involves the movement of heated air (fluid). This type of heat transfer is Convection.

Match Processes with Choices

The correct choice must match Heat Transfer with: I. Radiation, II. Conduction, III. Convection. Therefore, the correct answer is: a. I. Radiation; II. Conduction; III. Convection.

Key concepts

Radiation

Radiation is a form of heat transfer that does not require a medium; it can occur even through a vacuum. This is because radiation involves the transfer of energy via electromagnetic waves, such as visible light, infrared, and ultraviolet rays. An excellent example of radiation is the heat we receive from the Sun. Even across the vast emptiness of space, the Sun’s energy reaches Earth, warming our planet.

Other instances of radiation include heat emanating from a light bulb or the warmth you feel when sitting near a fireplace.

• No medium required for heat transfer
• Involves electromagnetic waves
• Energy transfer across a vacuum

Remember, any process where heat is transferred through a medium-less space can be attributed to radiation.

Conduction

Conduction is the process of heat transfer through direct contact. When two objects of different temperatures touch, the heat moves from the hotter object to the colder one until both reach the same temperature. The primary mechanism behind conduction is the collision and interaction of particles.

For example, if you place a metal spoon into a pot of hot soup, the heat from the soup is directly transferred to the spoon through conduction. Suppose you hold the spoon for too long; the heat will eventually reach your hand. This same process explains why metal feels hotter or colder compared to wood.
Here are key points about conduction:

• Direct contact required
• Particles collide and transfer energy
• Occurs mainly in solids but also in liquids and gases to a lesser extent

Convection

Convection is the transfer of heat by the movement of fluids, which can be liquids or gases. This process occurs when a fluid is heated, causing it to expand and become less dense. The less dense fluid rises, and the cooler, denser fluid sinks, creating a cycle of heat transfer.

A common example of convection is boiling water. As the water at the bottom of the pot heats up, it rises to the surface, and the cooler water moves down to replace it, creating a convection current. Another example is the rising plume of smoke from a fire, where the heated air carries the smoke upward.
Key points about convection include:

• Involves movement of fluids
• Caused by changes in density
• Creates convection currents