Download Water Cycle Study Guide

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The Water Cycle Study Guide
 About ¾ of the Earth is covered with water.
 All most all of that water is ocean water.
 Even though the ocean water is salty, it provides a large amount of Earth’s fresh
water.
 Earth’s water is always being recycled.
 Heat from the sun causes fresh water to evaporate from the oceans, leaving the
salt behind. This evaporated water condenses to form clouds. Fresh water falls
from the clouds to Earth’s surface as rain, snow, sleet, or hail. This constant
recycling of water is called the water cycle.
 During the cycle, water changes from a liquid to a gas and back to a liquid.
 The water cycle – the constant recycling of water from Earth’s surface, to the
atmosphere, and back to Earth’s surface again.
 Evaporation
 Condensation
 Precipitation
Ocean Water
 Ocean water is a mixture of water and many dissolved solids. Most of these
solids are salts.
 Sodium chloride is the most common salt in ocean water. It is also known as
table salt.
 Most of the salts and other substances in the ocean come from the land. As rivers,
streams, and runoff flow over the land, they slowly break down the rocks that
make it up. Over time, flowing water carries substances from the rocks to the
ocean.
 Near places where rivers empty into the ocean, the ocean water is less salty than it
is farther from the shore. This is because the fresh water mixes with the salt
water.
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 Ocean water is a little saltier near the equator, where it is hot and water evaporates
faster.
 Ocean water is al little less salty near the North and South Poles, where it is
colder and water evaporates more slowly.
Review
1. How does water change from a liquid to a gas and back to a liquid in the water cycle?
Answer: As air temperature increases, water evaporates from Earth’s surface. The gas
molecules rise, cool, and condense to form liquid water.
2. What factors affect the saltiness or density of ocean water?
Answer: Closeness to river mouths and the rate of evaporation; the latter depends on
temperature. Also, refer to the information above about the Equator and the North and
South Poles about saltiness of the ocean water.
Harcourt Science D34-37