Is possible in Blender to give models sizes. For example I would like to create a spoon and it should be 10 cm long.

Not that I’m aware of. You just have to look at the squares and say to yourself “Ok, one of those is 1cm square”. You can change the number of division by going to View->View Properties so you could make each square divide into 12 so you could have inches and feet if you fancied. But Blender isn’t a CAD program.