pH of water is 7.0 at ${25}^{0}C.$ If water is heated to ${70}^{0}C$, the

On heating water ${\text{K}}_{\mathrm{W}}$ increases and thus pH scale for neutrality changes from 7 to some lower value, i.e., 6.8 or 6.3depending upon ${\text{K}}_{\mathrm{W}}$ values.