Are Zero and Open conditional the same thing, or are Open and First conditional the same? Which conditional do you use 'when' with?
The zero conditional is a structure used for talking about general truths -- things which always happen under certain conditions
If you heat water to 100 degrees, it boils.
Phosphorus burns if you expose it to air.
These typically refer to the furute and the condition may or may not be fulfilled.
Open conditionals and first conditionals are basically the same. Most grammar books include the "zero conditionals " in this group too.