All the water evaporated about a million years ago and left the rock behind.

If so, this is the reason its water evaporates faster.

While the water evaporates from the lake, the salt remains.

If the water evaporates instantly, turn the heat down and test again in 3 minutes.

So water evaporates much more slowly the lower the temperature gets.

Not a small amount, if you imagine the water evaporating all year 'round.

Take off the lid, turn the heat up to high and cook until all the water has evaporated.

So eventually all the water will evaporate from an open container.

Check to be sure there is enough liquid; if the water has evaporated, add more.

Even with such measures, liquid water on Earth would evaporate in about 2.5 billion years from now.