• Changes in materials
    Irreversible changes, like burning, cannot be undone. Reversible changes, like melting and dissolving, can be changed back again. Introdu...
  • Food Chains and Cycles
    Food chains show the feeding relationships between living things. Pyramids of biomass reveal the mass of living material at each stage in ...
  • Animal Adaptations
    Animal Adaptations This planet is full of different animals. They can be easily found anywhere. They are easily adapted to conditions o...