This is a good visual for the part of the unit on identifying types of seeds. The students' will be able to see that not all seeds look the same. They will see the significant differences in shape and size.
Get a paper towel and wrap your apple seeds in them. Wet the paper towel and put it in the plastic bag. Make sure the plastic bag is sealed tight, and put it in the fridge. Your seeds should take about a month to germinate but check every few weeks and wet again if dry. Your seeds will start to have little white sprouts coming out of them soon enough that's when you know there ready for planting.