Understanding Pollution and the Water Cycle

Vocabulary

Pollution

Pollution is any substance added to the environment that negatively impacts the environment or its organisms.

Smog

Smog is a type of air pollution where gases from burning fossil fuels react with sunlight to form a fog.

Particulate Matter

Particulate matter consists of microscopic particles of dust, metal, and unburned fuels produced by industrial processes.

Acid Rain

Acid rain is precipitation with a decreased pH due to atmospheric pollutants. It contains elevated levels of hydrogen ions and is caused by sulfur and nitrogen oxide emissions from factories and power stations.

Greenhouse Effect

The greenhouse effect is the natural warming process where gases like carbon dioxide, methane, and water vapor trap heat in the Earth's atmosphere. These gases absorb thermal infrared radiation emitted from the Earth's surface.

Global Warming

Global Warming refers to the ongoing increase in average global temperatures.

The waste products from burning fossil fuels, such as gas and oil, produce ground-level ozone. While ozone is a pollutant harmful to human health, it also shields the Earth from ultraviolet rays.

Main Pollutants

• Smog
• Ground-level ozone

Effects of the Greenhouse Effect

• Increased tropical storms
• Melting of polar ice sheets
• Rising sea levels
• Destruction of cool-temperature ecosystems

The Water Cycle

What is the water cycle? It's the continuous movement and existence of water on, in, and above the Earth. Water constantly changes states—liquid, vapor, and ice—and this cycle has sustained life for billions of years.

Evaporation

Evaporation occurs when the sun heats water in rivers, lakes, or oceans, transforming it into vapor or steam. This vapor rises into the atmosphere.

Condensation

As water vapor in the air cools, it changes back into liquid droplets, forming clouds. This process is called condensation.

Precipitation

Precipitation happens when condensed water droplets in clouds become too heavy for the air to hold. Water falls back to Earth as rain, hail, sleet, or snow.

Collection

After precipitation, water may return to oceans, lakes, or rivers. On land, it either seeps into the ground as groundwater, which plants and animals use, or flows over the surface, eventually returning to bodies of water, restarting the cycle.