He'd left a pan of water on the stove and it had boiled dry.
Don't let the lentils boil dry.
Check the fish now and then to make sure it hasn't boiled dry.
Top up the water level regularly so that it doesn't boil dry.
Never allow a pan to boil dry as it will shorten its life.
You don't want the beans to boil dry - they'll burn.
See also: boil verb (HEAT LIQUID)