Press and hold the Power button until the Chromebook turns off
Wait a few seconds
Press the Power button again to turn it back on
If the Chromebook is frozen, press and hold Refresh and Power at the same time
Release both keys when the Chromebook restarts
If needed, close the lid, wait a few seconds, and open it again
If the Chromebook is plugged in and unresponsive, disconnect and reconnect the charger, then restart it