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Water and Its Properties

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Water and Its Properties

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    1. Water and Its Properties Section 15.1 new book

    2. Water molecules are polar

    3. file:///C:/Chemistry%20PresentationExpress/Chapter15/Section01/ChemASAP/dswmedia/rsc/asap1_chem05_cman1519.html

    4. Water in the Liquid State Polar molecules are attracted to one another by dipole interactions. The negative end of one molecule attracts the positive end of another molecule. The polarity of the water molecule results in hydrogen bonding. a) Partial negative charges are on each oxygen atom; partial positive charges are on the hydrogen atom. b) Because of polarity, hydrogen bonds form. Inferring To form a hydrogen bond, what must be true about the hydrogen and the element to which it is hydrogen bonded?The polarity of the water molecule results in hydrogen bonding. a) Partial negative charges are on each oxygen atom; partial positive charges are on the hydrogen atom. b) Because of polarity, hydrogen bonds form. Inferring To form a hydrogen bond, what must be true about the hydrogen and the element to which it is hydrogen bonded?

    5. Water in the Liquid State The intermolecular attraction among water molecules results in the formation of hydrogen bonds. The polarity of the water molecule results in hydrogen bonding. a) Partial negative charges are on each oxygen atom; partial positive charges are on the hydrogen atom. b) Because of polarity, hydrogen bonds form. Inferring To form a hydrogen bond, what must be true about the hydrogen and the element to which it is hydrogen bonded?The polarity of the water molecule results in hydrogen bonding. a) Partial negative charges are on each oxygen atom; partial positive charges are on the hydrogen atom. b) Because of polarity, hydrogen bonds form. Inferring To form a hydrogen bond, what must be true about the hydrogen and the element to which it is hydrogen bonded?

    6. Importance of Hydrogen Bonding Hydrogen bonding results in high surface tension and low vapor pressure Surface Tension The inward force, or pull, that tends to minimize the surface area of a liquid is called surface tension. All liquids have a surface tension, but water’s surface tension is higher than most. Water’s surface tension is higher than most due to the strong hydrogen bonding between molecules.

    7. Water in the Liquid State Surface tension makes it possible for this water strider to walk on water. file:///C:/Chemistry%20PresentationExpress/Chapter15/Section01/ChemASAP/dswmedia/rsc/asap1_chem05_cman1520.html Surface tension makes it possible for some insects, such as this water strider, to walk on water. Water molecules at the surface of the water drop above cannot form hydrogen bonds with air molecules, so they are drawn into the body of the liquid, producing surface tension.Surface tension makes it possible for some insects, such as this water strider, to walk on water. Water molecules at the surface of the water drop above cannot form hydrogen bonds with air molecules, so they are drawn into the body of the liquid, producing surface tension.

    8. Properties of Water A surfactant is any substance that interferes with the hydrogen bonding between water molecules and thereby reduces surface tension Will a bug still be able to walk on water that has been mixed with a few drops of detergent (a surfactant)? Vapor pressure: the pressure of vapor resulting from evaporation of a liquid above a sample of the liquid in a closed container. Water has a low vapor pressure compared to other substances with molecules of similar size. Because hydrogen bonds hold water molecules to one another, the tendency of these molecules to escape is low, and evaporation is slow. Slow evaporation results in fewer molecules above the surface of the liquid, resulting in fewer collisions of particles with the container and less vapor pressure

    9. Significance of Low Vapor Pressure Low Vapor Pressure A lower vapor pressure means it takes more energy to get the particles of the substance to escape into a gaseous form This means the boiling point of a substance with low vapor pressure is high High Vapor Pressure A higher vapor pressure means it takes less energy to get the particles of the substance to escape into a gaseous form This means the boiling point of a substance with high vapor pressure is low. Which has a higher boiling point:

    10. Water as a liquid and as a solid 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 starts to decrease. Most substances increase in density or contract when they freeze Water decreases in density and expands when it freezes This is due to hydrogen bonding

    12. Comparison of Water and Ice The structure of ice is a regular open framework of water molecules arranged like a honeycomb. When ice melts, the framework collapses, and the water molecules pack closer together, making liquid water more dense than ice.

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