The temperature of a sample of liquid water changes from 50°c to 30°c. which statement best explains the change that must happen at the molecular level?

a. the molecules move more quickly and their average kinetic energy increases.
b. the molecules move more slowly and their average kinetic energy decreases.
c. the molecules move more quickly and their average kinetic energy decreases.
d. the molecules move more slowly and their average kinetic energy increases

B. The molecules move more slowly and their average kinetic energy decreases.

Explanation: Kinetic energy is the energy possessed by a body by virtue of its motion.

Average kinetic energy is defined as the average of the kinetic energies of all the particles present in a system. It is determined by the equation:

R = gas constant

T = temperature of system

From above, it is visible that kinetic energy is directly related to the temperature of the system. So when the temperature is decreased from to ,the average kinetic energy of the system will also decrease and the molecules will start moving more slowly.

conduction is the transfer of thermal energy (heat in transfer) due to collisions between the molecules in the object. collisions between adjacent atoms and molecules transfer kinetic energy from the warmer to the cooler object. the objects must be in physical contact.