The Water Cycle
The same water you drink might have once been inside a dinosaur!
Goal:
Goal:
Water has been recycled through the water cycle since the beginning of life on Earth; that means the amount of fresh water on Earth never changes. The amount of fresh water currently on Earth is the same as what was present when the dinosaurs roamed.
Water is recycled through a process known as the water cycle. The water cycle is the continuous movement of water on the Earth's surface, underground, and in the atmosphere. This movement of water plays an essential role in supporting life on Earth. The water cycle can be broken down into three parts.
- Evaporation (liquid to gas)
- Condensation (gas to liquid)
- Precipitation (gas to liquid or solid)
As the temperature begins to warm, ice and snow melt from the tops of mountains and begin to flow down as freshwater streams that eventually meet up with rivers, lakes, or the ocean. The force of gravity pushes water from the tops of tall mountain ranges down until it flows into a lake or the ocean. Energy from the Sun shining on water is transferred to the individual water molecules that begin to warm up. Remember, when water molecules warm up, they gain energy and start moving around faster and faster until they change from a liquid and into a gas as water vapor--they evaporate. When water evaporates, the water molecules are purified or cleaned. This is important because the largest amount of evaporation occurs from the surface of the Earth's oceans, and we know the oceans are salt water. When water evaporates from the ocean into the atmosphere, the salt is left behind. Fresh, pure water becomes water vapor.
The higher you go in the atmosphere, the colder the air becomes. As water vapor molecules rise in the atmosphere, they begin to cool down, loose energy, slow down, and join back up with one another. These tiny liquid water droplets form clouds through condensation. You have probably seen condensation as fog in the early morning or as the water beads that collect on the outside of a glass of ice water. The water droplets in the atmosphere condense, or join back together, to form the clouds we see in the sky.
When water droplets in the clouds become too heavy, gravity pulls them down to Earth as rain, or snow if the temperature is cold enough. The liquid rain and solid snowflakes fall from the sky onto Earth’s surface to seep into the ground or collect in another body of water. Then, the whole process of the water cycle begins again!
Match each part of the water cycle to the correct explanation.