Water Cycle Lecture Notes

Definition of the Water Cycle: The water cycle is described as the process of water moving around between the air and the land.
Scientific Definition: In more scientific terms, the water cycle is the process of water evaporating and condensing on planet Earth in a continuous process.
Historical Longevity: This process has been occurring continuously for millions of years.
Biological Necessity: This cycle is essential for life; without it, there would be no life on Earth.

Process Overview: Water evaporates from the Earth’s surface.
Transformation of State: Evaporation is the process of water turning from a liquid into a gas. This gas form is specifically called water vapor.
Everyday Observation: An example provided is spilling a glass of water outside; after a few hours, the water is gone because it has turned into water vapor.
Visibility: Because water in its gas form (water vapor) has no color, it is invisible as it enters the air.
Role of Solar Energy: The evaporation of water outside is powered by the sun.
Temperature Correlation: Evaporation happens faster on a hot day. The hotter the temperature outside, the faster the water will evaporate.

Process Overview: Water vapor rises up into the sky due to the heat provided by the sun.
Transformation of State: Condensation is the process of water turning from a gas back into a liquid. This occurs once the water vapor rises high enough in the atmosphere.
Cloud Formation:
- Most water vapor rises high in the sky to form clouds.
- Fun Fact: Clouds are comprised of tiny water droplets numbering in the billions and billions.
Ground-Level Condensation (Dew and Fog):
- Not all water condenses high in the sky.
- Some water condenses close to the ground to form dew.
- Some water rises only a small amount to form fog.
The Cold Glass Analogy: Condensation can be experienced with a cold glass of water at a restaurant. As the cold glass sits, water vapor from the surrounding air condenses into liquid water droplets on the exterior of the glass.

Process Overview: Water falls back to the Earth as precipitation when water droplets in the clouds become heavy enough.
Forms of Precipitation: Precipitation can occur in several different ways depending on state and size:
- Rain: Liquid water.
- Snow: Frozen water.
- Hail: Large pieces of frozen water.
Cyclical Continuity: Precipitation returns water to the Earth, where the sun eventually shines on it again to restart the evaporation process, completing the cycle.

Drying Clothes Outside: Before the invention of drying machines, people dried washed clothes outside. This is possible through the process of evaporation, where liquid water in the clothes turns into gas.
Weekly Weather Patterns: Periodic rain or snow is a direct result of the water cycle.
Meteorology: Scientists known as meteorologists study the movement of water throughout the atmosphere to predict upcoming weather patterns.
Snow Days: The variety of precipitation forms (snow and hail) can lead to school closures, referred to as snow days.

Evaporation: When a liquid turns into a gas.
Condensation: When a gas turns into a liquid.
Water Vapor: Water in gas form.
Water Cycle: The cycle of water evaporating and condensing on Earth, which has been happening for millions of years.
Dew: Condensation found on the ground, usually on grass.
Clouds: Tiny droplets of condensed water vapor floating high above the ground.

Evidence of Water Vapor: We know water vapor exists in the air through several pieces of evidence:
- The presence of clouds.
- The sensation of moisture on the skin on humid days.
- The formation of droplets (condensation) on the surface of cold drinks.
Drivers of State Changes: Water changes form in response to temperature changes.
- Cooling: When temperatures become colder, water vapor becomes liquid water.
- Heating: When temperatures become warmer, liquid water becomes water vapor.
Purification via Evaporation: Generally, water becomes cleaner when it evaporates. This is because particles (impurities) in the water typically do not evaporate with the water vapor; they are left behind as the vapor rises.
DIY Solar Bowl Investigation Findings: In this specific investigation, the dirt and grass were left behind in the bowl during condensation on the plastic covering. This occurred because the dirt and grass were too heavy to evaporate.
The Distillation Process: In distillation, water is heated until it transforms into water vapor. The vapor then rises and enters a special tube designed to allow the vapor to cool down and return to a liquid state.