The Atmosphere and Air
The Earth is surrounded by a thick layer of air called the atmosphere.
- Composition: Air is a mixture of gases (mostly Nitrogen and Oxygen), water vapor, and dust particles.
- Moving Air: Moving air is called wind. A gentle wind is a breeze, while a strong wind is a storm.
- Land and Sea Breezes: The chapter explains how air moves near coastal areas:
- Sea Breeze: During the day, cool air from the sea blows toward the land.
- Land Breeze: At night, cool air from the land blows toward the sea.
Water and Its States
Water exists in three forms: solid (ice), liquid (water), and gas (water vapor).
- Evaporation: The process by which water changes into water vapor due to the sun’s heat.
- Condensation: The process by which water vapor cools down and changes back into water droplets (forming clouds).
The Water Cycle
This is the continuous journey of water from the Earth’s surface to the sky and back again.
- The sun heats water in oceans and rivers (Evaporation).
- Water vapor rises and cools to form clouds (Condensation).
- Water falls back to Earth as rain, snow, or hail (Precipitation).
Weather and Seasons
- Weather: The condition of the atmosphere at a particular place and time (e.g., sunny, cloudy, or rainy). It can change from hour to hour.
- Factors Affecting Weather: The sun, wind, clouds, and rain are the main factors that decide the weather.
- Seasons: When the same type of weather continues for a few months, it is called a season (Summer, Winter, Monsoon).
Key Vocabulary
