Water and Its Properties Essential Question: What makes water so important?

What are some of water’s roles on Earth?

Influencing Weather All weather is related to water. Water constantly moves from the Earth’s surface to the atmosphere as a result of evaporation. Condensation of water vapor forms clouds. Clouds produce rain, hail, sleet and snow.

Shaping Earth’s Surface Flowing rivers and pounding ocean waves slowly wear away rock and carry away sediment and soil. Glaciers (rivers of frozen ice) scrape away rocks and soil depositing these sediments elsewhere when the glacier melts.

Supporting Life Living things are largely made up of water. Nearly all biological processes use water. Clean water is vital to humans for survival and good health.

Supporting Human Activities Agriculture (irrigating crops, watering farm animals) Industry (manufacturing, hydroelectric power, mineral extraction, cleaning industrial products) Household Use (drinking, bathing, cleaning, gardening)

What is the structure of a water molecule?

Water (H 2 O) is a “polar” molecule. The hydrogen atoms have a small positive charge while the oxygen atom has a small negative charge. Since a water molecule has a positive end and a negative end, it is said to have “polarity.”

What states of water occur on Earth? Glaciers, ice sheets, icebergs, and some forms of precipitation are examples of how Earth’s water exists as ice. Most of Earth’s water is in the liquid form in rivers, lakes and oceans. Water vapor (gaseous water) exists in the atmosphere. When this water vapor condenses, clouds form.

What are four properties of water? The polarity of water molecules affects the properties of water. Water’s polarity affects how water molecules interact with one another and with other types of molecules.

Cohesion Cohesion is the property that holds molecules of a substance together. Because of their polarity, water molecules stick together tightly. The positive hydrogen ends of water molecules are attracted to the negative oxygen ends of other water molecules holding the molecules together. Because of cohesion, water forms droplets.

Adhesion Adhesion is the property that holds molecules of different substances together. “Wettable” substances attract water molecules more strongly than water molecules attract each other, so water sticks to them. (Example: Paper Towels) Water drops role off of unwettable (or waterproof) surfaces which are made of non- polar molecules.

Specific Heat Specific heat is the amount of heat needed to heat a substance by a particular amount. The attraction between polar water molecules means that separating them takes a great deal of energy. This means the specific heat of water is high, so water can absorb more energy than many other substances.

Water as a Solvent A liquid that dissolves substances is called a solvent. Because of its polarity, water dissolves many substances. For this reason, water is often referred to as the universal solvent. Water transports vital dissolved substances through, and allows for chemical reactions to take place inside organisms.