Properties of Water

ACTIVITY (5-7 minutes) You and your table partner will create THREE Water Molecules with the materials given You MUST LABEL the Oxygen Atom, the Hydrogen Atoms, and the Covalent Bonds with markers When finished, you MUST show the attraction bonds, HYDROGEN BONDs, between your three Water Molecules Tape the 3 molecules with the HYDROGEN Bond between them on the wall or window

Quick Write for 2 minutes: What makes water so special? 1

Properties of Water High Heat of Vaporization Polarity Cohesion High Heat of Fusion Less Dense as a Solid Universal Solvent Disassociation Polarity Cohesion Surface Tension Adhesion Capillary Action High Specific Heat 1

Water is Polar Oxygen has a partial (-) charge Hydrogen has a partial (+) charge Causes water to be POLAR, like a magnet

Covalent Bond vs. Hydrogen Bond VIDEO Covalent Bond

Polarity of Solvents LIKE Dissolves LIKE Solvents dissolve LIKE substances For instance, POLAR solvents (like water) dissolve only POLAR or IONIC substances In addition, NON-POLAR substances (like acetone) dissolve only NON-POLAR substances. LIKE Dissolves LIKE

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Cohesion Water molecules attracted to each other creating surface tension 1

Surface Tension The tightness across the surface of water caused by cohesion Makes the surface act like a solid 1

Adhesion Water molecules are attracted to other substances such as glass, soil, and plant tissues 1

Capillary Action Ability of water to “climb” up against gravity Results from Cohesion + Adhesion EX: Water moving up the roots to the top of the tree 1

High Specific Heat Amount of heat (energy) required to raise the temperature of water by 1⁰ C Example: WATER = 75°F BEACH = 110°F 1

High Heat of Vaporization Hydrogen bonds must break before water can transition from a liquid phase to a gas phase (water vapor)

High Heat of Vaporization When these hydrogen bonds break they absorb a lot of energy, leaving the water molecules behind cooler.

High Heat of Fusion Amount of energy it takes to turn a liquid into a solid. For water, it takes 80 calories of Heat to turn 1 gram of water into 1 gram of ice. Water is one of the few substances that are less dense as a solid than as a liquid. While other materials contract when they solidify, water expands. The cause of this exotic behavior is, once again, hydrogen bonding. At temperatures above 4º C, water behaves like other liquids, expanding as it warms and contracting as it cools. Water begins to freeze when its molecules are no longer moving vigorously enough to break their hydrogen bonds. As the temperature reaches 0º C, the water becomes locked into a crystalline lattice, each water molecule bonded to the maximum of four partners. The hydrogen bonds keep the molecules far enough apart to make ice about 10% less dense than liquid water at 4º C. When ice absorbs enough heat for its temperature to increase to above 0º C, hydrogen bonds between molecules are disrupted. As the crystal collapses, the ice melts, and molecules are free to slip closer together. Water reaches it greatest density at 4º C and then begins to expand as the molecules move faster.

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Water is Less Dense as a Solid Water in a liquid state keeps rebonding and changing its shape Water in a solid states has a fixed shape with space in between making it less dense 1

Quick Write – 2 minutes If ice were more dense than liquid water, how would this impact the survival of marine life?

Let’s Check our Answers If ice were more dense than liquid water, how would this impact the survival of marine life? VIDEO 1

High Heat of Fusion Ice forms from the top down Water is one of the few substances that are less dense as a solid than as a liquid. While other materials contract when they solidify, water expands. The cause of this exotic behavior is, once again, hydrogen bonding. At temperatures above 4º C, water behaves like other liquids, expanding as it warms and contracting as it cools. Water begins to freeze when its molecules are no longer moving vigorously enough to break their hydrogen bonds. As the temperature reaches 0º C, the water becomes locked into a crystalline lattice, each water molecule bonded to the maximum of four partners. The hydrogen bonds keep the molecules far enough apart to make ice about 10% less dense than liquid water at 4º C. When ice absorbs enough heat for its temperature to increase to above 0º C, hydrogen bonds between molecules are disrupted. As the crystal collapses, the ice melts, and molecules are free to slip closer together. Water reaches it greatest density at 4º C and then begins to expand as the molecules move faster. Ice forms from the top down Acts as an insulator; frozen lakes

Universal Solvent Water is called the universal solvent because it dissolves more substances than any other liquid Water dissolves polar substances and ionic compounds due to its polarity. 1

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