Cooling a substance before measurement is important from a chemistry perspective, particularly when dealing with hygroscopic materials. Hot samples can cause convection currents in the surrounding air, leading to inaccuracies in mass measurements due to the ascending force created by the warm air. Additionally, cooling helps prevent the sample from reabsorbing moisture from the air, which is critical for hygroscopic salts. Analytical balances are typically calibrated at room temperature, making it essential to allow samples to cool to ensure accurate readings.