Transfer of Thermal Energy (P2.3)

Front

Thermal conduction

Back

The transfer of thermal energy through a substance

Answer explanation

Thermal conduction is defined as the transfer of thermal energy through a substance, typically occurring in solids where heat moves from hotter to cooler areas. This distinguishes it from other processes like fluid heating or radiation.

Front

Why does thermal conduction occur faster in metals than in non-metals?

Back

Metals have free electrons that speed up energy transfer

Answer explanation

Thermal conduction occurs faster in metals because they have free electrons that facilitate rapid energy transfer, unlike non-metals, which lack these mobile charge carriers.

Front

When does thermal conduction end?

Back

When thermal equilibrium is reached

Answer explanation

Thermal conduction ends when thermal equilibrium is reached, meaning there is no net heat transfer between substances. This occurs when their temperatures equalize, regardless of particle movement or heating/cooling.

Front

Thermal equilibrium

Back

A state with no net energy transfer

Answer explanation

Thermal equilibrium is defined as a state with no net energy transfer between systems. This occurs when two systems reach the same temperature, resulting in no heat flow, making the correct choice 'A state with no net energy transfer'.

Front

True or False: Thermal conduction does not happen in liquids or gases.

Back

False

Answer explanation

False is correct because thermal conduction occurs in all states of matter, including solids, liquids, and gases. In liquids and gases, conduction happens through molecular collisions and energy transfer.

Front

What is a convection current?

Back

The movement of fluid due to temperature differences

Answer explanation

A convection current is the movement of fluid caused by temperature differences, where warmer, less dense fluid rises and cooler, denser fluid sinks, creating a continuous circulation pattern.

Front

What substance is used to demonstrate convection in water? Options: Potassium permanganate, Sodium chloride, Sugar, Vinegar

Back

Potassium permanganate

Answer explanation

Potassium permanganate is commonly used to visualize convection currents in water due to its distinct color. When added to water, it disperses as the water heats up, clearly demonstrating the movement of warmer water rising and cooler water sinking.

Front

True or False: Heat is a substance that can rise.

Back

False

Answer explanation

Heat is not a substance; it is a form of energy. It cannot rise like a material object. Therefore, the statement is false.

Front

What happens when a fluid is cooled?

Back

The particles move closer together and density increases

Answer explanation

When a fluid is cooled, its particles lose energy and move closer together, resulting in an increase in density. This is why the correct answer is that the particles move closer together and density increases.

Front

True or False: All objects emit thermal radiation.

Back

True

Answer explanation

True. All objects, regardless of their state (solid, liquid, or gas) and temperature, emit thermal radiation. This emission occurs due to the motion of particles within the object.