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B7 H) The Water Cycle
B7 H) The Water Cycle
The water cycle is also known as the hydrological cycle. The water cycle shows how water moves from one place to another, and how it is constantly being recycled. The water cycle is shown below.
Water evaporates from the sea and stores of water on land into the atmosphere. Stores of water on land includes lakes, rivers and reservoirs. Evaporation is where energy from the sun causes liquid water to turn into water vapour and enter the atmosphere. Water also enters the atmosphere when it evaporates from plants; water entering the atmosphere from plants is known as transpiration.
The water vapour that enters the atmosphere rises because warm gases rise. As water vapour rises, it cools and condenses to form clouds. Moisture in cloud form is transported around the earth by winds. Eventually, the water in clouds falls down to the surface of earth as precipitation (rain, snow, sleet and hail). Precipitation is important as it provides fresh water for plants and animals.
After the fresh water from precipitation hits the surface of earth, the water can go to a few different places.
The water vapour that enters the atmosphere rises because warm gases rise. As water vapour rises, it cools and condenses to form clouds. Moisture in cloud form is transported around the earth by winds. Eventually, the water in clouds falls down to the surface of earth as precipitation (rain, snow, sleet and hail). Precipitation is important as it provides fresh water for plants and animals.
After the fresh water from precipitation hits the surface of earth, the water can go to a few different places.
- Some of the water that falls on the surface of earth becomes part of the soil. Plants take in some of the water in the soil. They use some of this water for photosynthesis (carbon dioxide + water –> glucose + oxygen). Also, some of the water that plants take in becomes part of the tissue of the plants. When the plants are eaten by another organism, the water stored in the plant’s tissue is passed onto the organism that eats the plant (water is passed through the food chain). Water also leaves plants through the leaves and enters the atmosphere; this is known as transpiration.
- Animals take in water by drinking it. The animals use the water for chemical reactions and store it in tissue. Water leaves animals by excretion (getting rid of waste products – urine and faeces), sweating and breathing (water vapour is released when we breath out).
- The majority of water that lands on the surface of earth works its way to rivers that lead to the sea. Water then evaporates and the whole process starts again.