Water is very important to living things. Without water there can be no life on the earth. All animals and plants need water. Man also needs water. We need water to drink, to cook our food and to clean ourselves. Water is needed in offices, factories and schools. Water is needed everywhere. There is water in seas, rivers and lakes. Water is found almost everywhere. Even in the desert part of the world, there is some water in the air. You can not see or feel it when it is a part of the air. The water in the seas, rivers and lakes is a liquid, the water in the air is a gas, and we call it water vapor (蒸气). Clouds are made of water. They may be made of very small drops of water. They may also be made of snow crystals(结晶体). Snow crystals are very small crystals of ice. Ice is frozen water. It is a solid. There can be snow and ice everywhere in winter. Water may be a solid or a liquid or a gas. When it is a solid, it may be as hard as a stone. When it is a liquid, you can drink it. When it is a gas, you can not see or feel it. Where can we find water?