SCIENCE CHAPTER 6 WATER CYCLE AND WEATHER

LESSON 1 Where is Earth’s Water ?

Lesson 1 ¾ of Earth’s surface is covered with water. Ocean Water/Fresh Water Ocean water is very salty. It is not healthy to drink. Fresh water is found underground, or in lakes, rivers, and streams.

Lesson 1 The ocean is less salty in areas where there are rivers, melting ice, or heavy rains that add plenty of fresh water. The Baltic Sea is less salty because many rivers flow into it.

LESSON 2 How do water and air affect weather?

Lesson 2 The never-ending movement of water from Earth’s surface to its atmosphere is the water cycle. The Sun’s purpose in the water cycle is to evaporate water. When moist air rises, it cools and the water vapor in it condenses and forms clouds.

Lesson 2 Condensation is the process of water vapor, a gas, changing to a liquid as it cools. Air is a mixture of invisible gas that surrounds Earth. If there is air near an area of low pressure that air will move toward the area of low pressure Air pressure decreases as you go higher in the atmosphere. –Air pressure becomes lower

LESSON 3 What are air masses?

Lesson 3 Humidity is the amount of water vapor in the air. The area where two air masses meet is called a front.

Lesson 4 There are two types of fronts: cold front, warm front Cold fronts form when a cold air mass bumps into a warm air mass that is not moving at all. The dense cold air sinks. The warm air is pushed upwards. Water vapor condenses into clouds. Clouds will usually form in a line along a cold front.