the diagram below shows the temperature dropping from 80°c to 20°c. 80 °c 20 °c molecules that have longer…
the diagram below shows the temperature dropping from 80°c to 20°c. 80 °c 20 °c molecules that have longer arrows are moving faster. which statement describes what is happening in this system? molecules vibrate more as temperature decreases. temperature is not related to the average kinetic energy of a system. kinetic energy decreases as temperature decreases. there is no change in average kinetic energy between these two systems.
Answer
Explanation:
Step1: Recall kinetic - energy and temperature relation
The average kinetic energy of molecules in a substance is directly proportional to the temperature of the substance. Mathematically, the average kinetic energy of gas molecules is given by $\overline{K.E.}=\frac{3}{2}kT$, where $k$ is the Boltzmann constant and $T$ is the absolute temperature.
Step2: Analyze the given temperature change
The temperature is dropping from $80^{\circ}C$ to $20^{\circ}C$. As the temperature decreases, according to the relation $\overline{K.E.}\propto T$, the average kinetic energy of the molecules also decreases.
Step3: Evaluate each option
- Option 1: Molecules vibrate less as temperature decreases, not more, so this is incorrect.
- Option 2: Temperature is directly related to the average kinetic energy of a system, so this is incorrect.
- Option 3: Since $\overline{K.E.}\propto T$, when $T$ decreases, kinetic energy decreases. This is correct.
- Option 4: There is a change in average kinetic energy as the temperature changes, so this is incorrect.
Answer:
Kinetic energy decreases as temperature decreases.