How many significant figures are in measurement 0.00304kg

Significant figures are numbers that are not 0s, but they are included if they are between two numbers:
There are three significant figures, 304

Hope this helps! :)

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.