Question

4 multiple choice 2 points
when one end of a short metal bar is heated, the opposite end will eventually become hot. which of the following processes transfers the heat through the bar?
condensation
conduction
convection
radiation
5 multiple choice 2 points
a barefoot student steps on a hot concrete surface. most of the heat transferred to the students skin by this contact is by the process of
convection
conduction
vaporization
radiation
6 multiple choice 2 points
in a laboratory, a sealed container with 100g of steam is cooled until all the steam becomes a liquid. the container is then cooled further until all the water becomes a solid.
which of the following remains constant during both of these changes?
the mass of the water
the pressure in the container
the total energy of the water
the position of the atoms in the container

Explanation:

• Question 4: Conduction is the transfer of heat through direct contact within a material (like the metal bar). Condensation is a phase - change process (gas to liquid), convection involves the movement of fluids (liquids or gases) to transfer heat, and radiation is heat transfer via electromagnetic waves (no medium needed).
• Question 5: When the barefoot student steps on the hot concrete, heat is transferred by conduction (direct contact between the concrete and the skin). Convection would require a fluid (like air or water) in motion, vaporization is a phase - change (liquid to gas), and radiation is non - contact heat transfer.
• Question 6: According to the law of conservation of mass, the mass of a substance remains constant during phase changes (steam to liquid to solid). The pressure in the container is likely to change during cooling (as the volume and state of the substance change), the total energy of the water changes (as heat is removed during cooling), and the position of the atoms changes (from the more disordered state in steam to the more ordered state in solid).

Answer:

• Question 4: B. conduction
• Question 5: B. conduction
• Question 6: A. the mass of the water