Worked example: Use the Curie law to compare the paramagnetic susceptibility of a salt with one unpaired electron per ion at 300 K and 30 K (Curie constant C = 0.375 cm³·K/mol for spin-½). Step 1: Curie law χ = C/T (molar susceptibility). Step 2: At 300 K: χ = 0.375/300 = 1.25×10⁻³ cm³/mol. Step 3: At 30 K: χ = 0.375/30 = 1.25×10⁻² cm³/mol — 10× larger. Step 4: Physical meaning: colder means less thermal randomisation, so moments align more easily — susceptibility diverges as T → 0 (until ordering or quantum effects intervene). Step 5: Contrast with Pauli paramagnetism of metals (temperature-independent) and diamagnetism (negative, tiny). Conclusion: χ ∝ 1/T is the fingerprint of localised unpaired moments — a quick susceptibility measurement identifies the magnetic species.