A student separately places identical amounts of gaseous ammonia and methane in rigid containers of equal volume. At each temperature, no condensation is observed. The student calculates the ideal-gas pressure using \(P_{\text{ideal}}V=nRT\) and records the following data.

Gas	\(\dfrac{P_{\text{measured}}}{P_{\text{ideal}}}\) at \(500\text{ K}\)	\(\dfrac{P_{\text{measured}}}{P_{\text{ideal}}}\) at \(300\text{ K}\)
\(\text{NH}_3\text{(g)}\)	\(0.98\)	\(0.95\)
\(\text{CH}_4\text{(g)}\)	\(1.02\)	\(1.01\)

Which of the following statements best explains why the pressure ratio for \(\text{NH}_3\text{(g)}\) is lower than that for \(\text{CH}_4\text{(g)}\) and decreases more upon cooling?