Question

Molecular motion shows itself as,
A. Temperature.
B. Internal energy.
C. Friction.
D. Viscosity.

Answer 1

Hint: First, the relation of molecular motion with temperature, internal energy, friction and
viscosity should be identified. It is necessary to understand that matter consists of moving
particles viz. atoms and molecules. This motion of particles forms the basis of kinetic theory.
The motion of molecular particles or molecules is increased by increasing temperature.
Conversely, the motion of the molecule is reduced by lowering the temperature. Since the
molecules are in motion, they have kinetic energy. Temperature is a measure of the average
kinetic energy of the particles. The molecular motion is directly proportional to the temperature.
It is not internal energy as internal energy is the sum of potential energy, kinetic energy,
electronic energy and nuclear energy of molecules. It cannot be friction as friction always acts
opposite to the direction of motion. Viscosity is again related to fluid and is a measure of its
resistance to deformation at a given rate.
When heat is added to a substance by increasing temperature, the molecules move faster as the
spacing between them increases. From this characteristic it can be determined that molecular
motion is directly related to temperature.
Hence, the correct answer is (A).
Note: In the solution, the students have to relate the theory of molecular motion with change in
temperature. From the kinetic theory, it is understood the behavior of a molecule and how the
molecules move when temperature is increased or decreased.