15.1 Water and Its Properties > 1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 1. Calculate and record your % grade. Quest 5 = ____ 2. Did you meet your goal? Why or why not. Day

15.1 Water and Its Properties > 2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 3. Locate your Chapter 1, 2, 3, & 4 Tests / Quests and record those grades as well: 4. Calculate your average test grade: Average test grade = ____

15.1 Water and Its Properties > 3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 5. SPECIFIC study (preparation) plan for next test? Next time I will study by … 6. Record your new goal: - Your average MUST improve by at least 1% point Day

15.1 Water and Its Properties > 4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Chapter 15 Water and Aqueous Systems 15.1 Water and Its Properties 15.2 Homogeneous Aqueous Systems 15.3 Heterogeneous Aqueous Systems

15.1 Water and Its Properties > 5 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. What properties of water make it essential to life on Earth? Water covers about three quarters of Earth’s surface. All known life forms are made mostly of water. CHEMISTRY & YOU

15.1 Water and Its Properties > 6 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Water, H 2 O, is a simple molecule consisting of three atoms. The oxygen atom forms a covalent bond with each of the hydrogen atoms. Oxygen has a greater electronegativity than hydrogen, so the oxygen atom attracts the electron pair of the covalent O—H bond to a greater extent than the hydrogen atom. Thus, the O—H bond is highly polar. Water in the Liquid State

15.1 Water and Its Properties > 7 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The oxygen atom acquires a partial negative charge (δ – ). The less electronegative hydrogen atoms acquire partial positive charges (δ + ). Water in the Liquid State Molecule has net polarity Polar bonds δ–δ– δ–δ– δ+δ+ δ+δ+ δ–δ– δ–δ– δ+δ+ δ+δ+

15.1 Water and Its Properties > 8 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The molecule has a bent shape. The two O—H bond polarities do not cancel. The water molecule as a whole is polar. How do the polarities of the two O—H bonds affect the polarity of the molecule? Water in the Liquid State Molecule has net polarity Polar bonds δ–δ– δ–δ– δ+δ+ δ+δ+ δ–δ– δ–δ– δ+δ+ δ+δ+

15.1 Water and Its Properties > 9 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. In general, polar molecules are attracted to one another by dipole interactions. The negative end of one molecule attracts the positive end of another molecule. Water in the Liquid State δ+δ+ δ+δ+ δ–δ–

15.1 Water and Its Properties > 10 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. However, in water, this attraction results in hydrogen bonding. Hydrogen bonds are attractive forces that arise when a hydrogen atom is covalently bonded to a very electronegative atom and also weakly bonded to an unshared electron pair of another electronegative atom. Water in the Liquid State Liquid water Hydrogen bond

15.1 Water and Its Properties > 11 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Many unique and important properties of water—including its high surface tension, low vapor pressure, and high boiling point—result from hydrogen bonding. Water in the Liquid State

15.1 Water and Its Properties > 12 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Vapor Pressure Hydrogen bonding between water molecules also explains water’s unusually low vapor pressure. An extensive network of hydrogen bonds holds the molecules in liquid water to one another. These hydrogen bonds must be broken before water changes from the liquid to the vapor state, so the tendency of these molecules to escape is low and evaporation is slow. Water in the Liquid State

15.1 Water and Its Properties > 13 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Water in the Solid State As water begins to cool, it behaves initially like a typical liquid. It contracts slightly, and its density gradually increases. When the temperature of the water falls below 4˚C, the density of water actually starts to decrease. Density of Liquid Water and Ice Temperature (˚C)Density (g/cm 3 ) 100 (liquid water) (liquid water) (ice)0.9168

15.1 Water and Its Properties > 14 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Water in the Solid State Below 4˚C, water no longer behaves like a typical liquid. Ice, which forms at 0˚C, has about a 10% lower density than water at 0˚C. Ice is one of only a few solids that floats in its own liquid. Density of Liquid Water and Ice Temperature (˚C)Density (g/cm 3 ) 100 (liquid water) (liquid water) (ice)0.9168

15.1 Water and Its Properties > 15 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Water in the Solid State The structure of ice is a regular open framework of water molecules in a hexagonal arrangement. The hexagonal symmetry of a snowflake reflects the structure of the ice crystal. Why is ice less dense than liquid water?

15.1 Water and Its Properties > 16 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Water in the Solid State The unique properties of ice are a result of hydrogen bonding. Extensive hydrogen bonding in ice holds the water molecules farther apart in a more ordered arrangement than in liquid water. Hydrogen bond Ice

15.1 Water and Its Properties > 17 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Water in the Solid State The fact that ice floats has important consequences for all organisms. The liquid water at the bottom of an otherwise frozen body of water is warmer than 0˚C, so fish and other aquatic life are better able to survive. If ice were denser than liquid water, bodies of water would tend to freeze solid during the winter months, destroying many types of organisms.

15.1 Water and Its Properties > 18 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. What properties of water that result from hydrogen bonding make it essential to life on Earth? The low vapor pressure of water keeps the liquid water in all of Earth’s lakes and oceans from evaporating rapidly. If water did not have such a high boiling point, it would be a vapor at the usual temperatures found on Earth. The fact that ice floats allows fish and other aquatic life to survive the winter months. CHEMISTRY & YOU

15.1 Water and Its Properties > 19 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Water molecules are held together through hydrogen bonds. The hydrogen bonding interactions between water molecules account for the unique properties of water, including its high surface tension, low vapor pressure, and high boiling point. Hydrogen bonding also accounts for the fact that ice is less dense than liquid water. BIG IDEA Bonding and Interactions

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