End Show Slide 1 of 44 Copyright Pearson Prentice Hall Biology

End Show Slide 2 of 44 Copyright Pearson Prentice Hall 2-2 Properties of Water

End Show 2-2 Properties of Water Slide 3 of 44 Copyright Pearson Prentice Hall The Water Molecule A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms.

End Show 2-2 Properties of Water Slide 4 of 44 An example of a hydrogen bond is the attraction between the H atom on one water molecule & the O atom on another water molecule. A hydrogen bond is weaker than an ionic or a covalent bond, but it is the strongest force that exists between molecules Copyright Pearson Prentice Hall

End Show 2-2 Properties of Water Slide 5 of 44 Copyright Pearson Prentice Hall The Water Molecule Water Molecule

End Show 2-2 Properties of Water Slide 6 of 44 Copyright Pearson Prentice Hall The Water Molecule Hydrogen Bonds Because of their partial positive and negative charges, polar molecules can attract each other.

End Show 2-2 Properties of Water Slide 7 of 44 Copyright Pearson Prentice Hall The Water Molecule Cohesion is an attraction between molecules of the same substance. Because of hydrogen bonding, water is extremely cohesive.

End Show 2-2 Properties of Water Slide 8 of 44 Copyright Pearson Prentice Hall The Water Molecule Adhesion is an attraction between molecules of different substances.

End Show 2-2 Properties of Water Slide 9 of 44 Copyright Pearson Prentice Hall Solutions and Suspensions A mixture is a material composed of two or more elements or compounds that are physically mixed but not chemically combined.

End Show 2-2 Properties of Water Slide 10 of 44 Copyright Pearson Prentice Hall Solutions and Suspensions Two types of mixtures can be made with water solutions – a mixture of two or more substances evenly mixed Suspensions – a mixture of water and a non- dissolved material

End Show 2-2 Properties of Water Slide 11 of 44 Copyright Pearson Prentice Hall Solutions and Suspensions Solutions All the components of a solution are evenly distributed throughout the solution. solute—the substance that is dissolved. solvent—the substance in which the solute dissolves.

End Show 2-2 Properties of Water Slide 12 of 44 Copyright Pearson Prentice Hall Solutions and Suspensions When a crystal of table salt is placed in warm water, sodium and chloride ions are attracted to the polar water molecules. Na + Cl - Water

End Show 2-2 Properties of Water Slide 13 of 44 Copyright Pearson Prentice Hall Solutions and Suspensions Suspensions Some materials do not dissolve when placed in water but separate into pieces so small that they do not settle out easily.

End Show 2-2 Properties of Water Slide 14 of 44 Copyright Pearson Prentice Hall Acids, Bases, and pH A water molecule is neutral, but can react to form hydrogen and hydroxide ions. H 2 O   H + + OH -

End Show 2-2 Properties of Water Slide 15 of 44 Copyright Pearson Prentice Hall Acids, Bases, and pH The pH scale Chemists devised a measurement system called the pH scale to indicate the concentration of H + ions in solution. The pH scale ranges from 0 to 14.

End Show 2-2 Properties of Water Slide 16 of 44 Copyright Pearson Prentice Hall Acids, Bases, and pH At a pH of 7, the concentration of H + ions and OH - ions is equal. The pH Scale Human blood Milk Sea water Normal rainfall Pure water

End Show 2-2 Properties of Water Slide 17 of 44 Copyright Pearson Prentice Hall Acids, Bases, and pH Acids An acid is any compound that forms H + ions in solution.

End Show 2-2 Properties of Water Slide 18 of 44 Copyright Pearson Prentice Hall Acids, Bases, and pH Bases A base is a compound that produces hydroxide ions (OH - ions) in solution.

End Show 2-2 Properties of Water Slide 19 of 44 Copyright Pearson Prentice Hall Acids, Bases, and pH Buffers The pH of the fluids within most cells in the human body must generally be kept between 6.5 and 7.5. Controlling pH is important for maintaining homeostasis.

End Show 2-2 Properties of Water Slide 20 of 44 A buffer is a weak acid or base that can react with a strong acid or base to prevent sudden changes in pH from occurring. Copyright Pearson Prentice Hall

End Show Slide 21 of 44 Copyright Pearson Prentice Hall 2-2 A molecule in which the charges are unevenly distributed is called a a.polar molecule. b.cohesive molecule. c.hydrogen molecule. d.covalent molecule.

End Show Slide 22 of 44 Copyright Pearson Prentice Hall 2-2 A dissolved substance is called a a.solvent. b.solution. c.solute. d.Suspension.

End Show Slide 23 of 44 Copyright Pearson Prentice Hall 2-2 A compound that produces hydroxide ions in solution is called a(an) a.base. b.buffer. c.acid. d.salt.

End Show Slide 24 of 44 Copyright Pearson Prentice Hall 2-2 Hydrogen bonds between water molecules result from a.adhesion between water molecules. b.magnetic attractions between water molecules. c.uneven electron distribution in each water molecule. d.ionic bonds in the water molecule.

End Show Slide 25 of 44 Copyright Pearson Prentice Hall 2-2 On a pH scale, a value of 2 means that the solution has a.equal concentrations of H + and OH - ions. b.the same concentration of H + ions as pure water. c.higher concentration of H + than in pure water. d.lower concentration of H + than in pure water.

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