This set includes:

Earth Is Tilting!
Gravity! Do You Feel It?
Let´s Classify Animals!
Melting Matter
Natural or Man-Made?
Plants Make Their Own Food
Seeds, Bees, and Pollen
Studying Weather and Climates
What Do Critters Do in the Winter?
What´s on the Food Chain Menu?
Where Did the Water Go?
Zap! It´s Electricity!

Twelve books total.