At 25 degrees Celsius, the ion product of water, denoted as \( K_w \), is \( 1.0 \times 10^{-14} \). This value is crucial to remember, as it serves as a reference point for understanding the behavior of water's ionization. \( K_w \) is an equilibrium constant, which means it is influenced by temperature changes. As the temperature increases, the value of \( K_w \) also tends to increase. This relationship can be observed across a range of temperatures, from 0 degrees Celsius to 100 degrees Celsius, where a clear trend shows that \( K_w \) rises with temperature.

It's important to note that if the temperature deviates from 25 degrees Celsius, you will be provided with the corresponding \( K_w \) value, as memorizing all possible values at different temperatures would be impractical. Understanding this temperature dependence of \( K_w \) is essential for grasping concepts related to acid-base chemistry and the behavior of aqueous solutions.