Why didnt they hatch?

Question

At school we were doing embryology. We got chicken eggs and we incubated them, turned them, checked the temperature, gave humidity. They didnt hatch we had 20 eggs! The second time a couple hatched yet one died. We ended up with a total of 4 live chicks out of about 50 (in both tries)! Some were opening but they didnt come out the second time we tried. What happened?!

Answer 1

THE EGGS WERE SOME TIMEPROBABLY EMPTY OR THE CHICKS DIED IN THE EGG. OR MAYBE SOMBODY REPLACED THEM WITH FAKE EGGS. OR MAYBE THEY NEED SOME TIME

Answer 2

Chicks starting to hatch but not making it out indicates that the humidity was not high enough.It needs to be increased in the last few days to allow the shells to soften. Even opening the incubator in the last few days can effect this as it disturbs the humidity.

Other thing may be that not all the eggs were fertile to begin with. Even with a rooster around it's not a sure thing that eggs will be fertile.

Transport, not storing them correctly before incubating or storing them too long (some say more than 7 days between laying and incubating is too long) or even not turning them enough while incubating can all lead to eggs not hatching.

There are a LOT of reasons why they may not have hatched. Without going through your process step by step it's really impossible to tell exactly why, and different eggs may not have hatched for different reasons.