2The Water MoleculeA water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms.
3Water Molecule The Water Molecule The unequal sharing of electrons causes the water molecule to be polar. The hydrogen end of the molecule is slightly positive and the oxygen end is slightly negative.
4The Water MoleculeHydrogen BondsBecause of their partial positive and negative charges, polar molecules can attract each other.
5Cohesion is an attraction between molecules of the same substance. The Water MoleculeCohesion is an attraction between molecules of the same substance.Because of hydrogen bonding, water is extremely cohesive.
6Copyright Pearson Prentice Hall The Water MoleculeAdhesion is an attraction between molecules of different substances.Copyright Pearson Prentice Hall
7Solutions and Suspensions A mixture is a material composed of two or more elements or compounds that are physically mixed but not chemically combined.
8Solutions and Suspensions Two types of mixtures can be made with watersolutionssuspensions
9Solutions and Suspensions 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.
10Solutions 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 -WaterWhen an ionic compound such as sodium chloride is placed in water, water molecules surround and separate the positive and negative ions.Copyright Pearson Prentice Hall
11Solutions and Suspensions Some materials do not dissolve when placed in water but separate into pieces so small that they do not settle out easily.Copyright Pearson Prentice Hall
12Acids, Bases, and pHAcids, Bases, and pHA water molecule is neutral, but can react to form hydrogen and hydroxide ions.H2O H+ + OH-
13Acids, Bases, and pHThe 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.
14At a pH of 7, the concentration of H+ ions and OH- ions is equal. The pH ScaleAcids, Bases, and pHAt a pH of 7, the concentration of H+ ions and OH- ions is equal.Sea waterHuman bloodPure waterMilkNormal rainfallThe concentration of H+ ions determines whether solutions are acidic or basic.
15Acids An acid is any compound that forms H+ ions in solution. Acids, Bases, and pHAcidsAn acid is any compound that forms H+ ions in solution.
16Acids, Bases, and pHBasesA base is a compound that produces hydroxide ions (OH- ions) in solution.
17Buffers 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.Neutralization: H OH- = H2OAcids, Bases, and pH
192-2A molecule in which the charges are unevenly distributed is called apolar molecule.cohesive molecule.hydrogen molecule.covalent molecule.
202-2 A dissolved substance is called a solvent. solution. solute. Suspension.
212-2A compound that produces hydroxide ions in solution is called a(an)base.buffer.acid.salt.
222-2 Hydrogen bonds between water molecules result from adhesion between water molecules.magnetic attractions between water molecules.uneven electron distribution in each water molecule.ionic bonds in the water molecule.
232-2 On a pH scale, a value of 2 means that the solution has equal concentrations of H+ and OH- ions.the same concentration of H+ ions as pure water.higher concentration of H+ than in pure water.lower concentration of H+ than in pure water.