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 it is frozen, press and hold Refresh and Power at the same time
Release both keys when the Chromebook restarts
If needed, close the lid and reopen it to wake the Chromebook
If the battery is removable, turn it off, remove the battery, reinsert it, and power it on again