Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface?Nonpolar groups attract one another.Polar groups repel water.Polar groups attract one another.Nonpolar groups repel water.All of the above.
  • DREASON: Good! When sugar dissolves in water, the sugar molecules remain intact but mingle with water molecules. When salt (NaCl) dissolves, its Na+ and Cl- ions separately mingle with water.
  • EREASON: Correct! The ice lattice has open spaces because of the angles at which hydrogen bonds form. Heat energy can break water molecules free of the lattice so they move into the openings.
  • CREASON: Good thinking! Polar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.
  • DREASON: Good choice! Random collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.
Polar attractions are ...(a) forces between atoms with partial charges.(b) weaker than covalent bonds.(c) important because they are numerous.(a) and (b) are true. (c) is false.(a), (b), and (c) are correct.
  • EREASON: Correct! The ice lattice has open spaces because of the angles at which hydrogen bonds form. Heat energy can break water molecules free of the lattice so they move into the openings.
  • BREASON: They can also form between H and other highly electronegative atoms, such as O, if the atoms have strong partial charges.
  • EREASON: Polar attractions occur between atoms with partial charges and are weaker than covalent bonds. Still, they're important because so many of them occur in living cells.
  • EREASON: Good choice! The hydrogen bonds between surface water molecules are normally slightly stretched. Like a stretched sheet of rubber, the surface tends to contract and resists being penetrated.
Though you add heat, the temperature of boiling water remains constant because ...water has a constant boiling temperature.it takes energy to break covalent bonds.it takes energy to break hydrogen bonds.it takes energy to circulate water.None of the above. The temperature rises during boiling.
  • CREASON: Correct! At boiling, all the added heat is used to break hydrogen bonds. Free of the water mass, the departing steam carries away all the added energy, with none left over to raise the temperature.
  • EREASON: Correct! The ice lattice has open spaces because of the angles at which hydrogen bonds form. Heat energy can break water molecules free of the lattice so they move into the openings.
  • DREASON: Good choice! Random collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.
  • CREASON: Good thinking! Polar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.
Which of these is the correct equation for the dissociation of water?H+<==> H2O + H2O+H2O + H2O <==> H3O+ + OH-H2O + OH-<==> H2O+H2O <==> H+ + OH-H2O + H2O+<==> H2O + OH-
  • CREASON: Good thinking! Polar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.
  • EREASON: Correct! The ice lattice has open spaces because of the angles at which hydrogen bonds form. Heat energy can break water molecules free of the lattice so they move into the openings.
  • BREASON: it makes H3O+ and OH-, not H+ and OH-
  • (a) A water molecule can make 4 hydrogen bonds.
Dissolving is best described as...molecules breaking into ions.a change from a solid to a liquid.a separation of molecules into neutral atoms.a mingling of molecules and/or ions.breaking covalent bonds.
  • DREASON: Good choice! Random collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.
  • DREASON: Good answer! Many reactions incorporate O and H from water into biological molecules. This happens when you digest starch and protein, for example.
  • CREASON: Good thinking! Polar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.
  • DREASON: Good! When sugar dissolves in water, the sugar molecules remain intact but mingle with water molecules. When salt (NaCl) dissolves, its Na+ and Cl- ions separately mingle with water.
Which factor is important in making it possible to cool yourself by sweating? Think carefully!(a) Molecules collide with varied angles and speeds.(b) Hydrogen bonds are relatively weak.(c) Water has more energy at the body surface.Both (a) and (b).(a), (b), and (c).
  • CREASON: Good thinking! Polar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.
  • EREASON: Correct! The ice lattice has open spaces because of the angles at which hydrogen bonds form. Heat energy can break water molecules free of the lattice so they move into the openings.
  • DREASON: Good choice! Random collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.
  • DREASON: Good! When sugar dissolves in water, the sugar molecules remain intact but mingle with water molecules. When salt (NaCl) dissolves, its Na+ and Cl- ions separately mingle with water.
Water is a source of ______________ for chemical reactions in cells.(a) hydrogen atoms(b) oxygen atoms(c) energyBoth (a) and (b)(a), (b), and (c).
  • CREASON: Good thinking! Polar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.
  • DREASON: Good! When sugar dissolves in water, the sugar molecules remain intact but mingle with water molecules. When salt (NaCl) dissolves, its Na+ and Cl- ions separately mingle with water.
  • DREASON: Good answer! Many reactions incorporate O and H from water into biological molecules. This happens when you digest starch and protein, for example.
  • DREASON: Good choice! Random collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.
About _____ molecules in a glass of water are dissociated.1 in 5,000,0001 in 1,000,0001 in 500,000,0001 in 21 in 1,000,000,000
  • DREASON: Good answer! Many reactions incorporate O and H from water into biological molecules. This happens when you digest starch and protein, for example.
  • The absorption of heat by the breaking of hydrogen bonds.
  • 10^-4
  • C
Which statement helps to explain why ice is less dense than liquid water?(a) Water molecules make hydrogen bonds at definite angles.(b) Cold molecules move less than warm molecules.(c) Hydrogen bonds lengthen in the cold.All of the above.Both (a) and (b).
  • CREASON: Good thinking! Polar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.
  • DREASON: Good choice! Random collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.
  • EREASON: Correct! The ice lattice has open spaces because of the angles at which hydrogen bonds form. Heat energy can break water molecules free of the lattice so they move into the openings.
  • CREASON: Correct! At boiling, all the added heat is used to break hydrogen bonds. Free of the water mass, the departing steam carries away all the added energy, with none left over to raise the temperature.
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