This learning resource explores the global distribution of water through a 100-liter model that visualizes the total water available on Earth. It explains the composition of the hydrosphere, highlighting the vast amount of saltwater compared to the minimal freshwater resources. The document discusses why most of Earth's water is unusable for drinking, focusing on the concept of salinity and its effects on human health. The resource also introduces the cryosphere, detailing its role in the Earth's water system, and concludes with a review section to reinforce the key concepts about liquid and frozen water.