A.P. Biology- Mrs. Wold 2.5

Though you add heat, the temperature of boiling water remains constant because ... it takes energy to circulate water. water has a constant boiling temperature. it takes energy to break covalent bonds. it takes energy to break hydrogen bonds. None of the above. The temperature rises during boiling. Previous Answers

it takes energy to break hydrogen bonds.

Part complete What is the charge on a hydroxide ion? 1+ 2+ 2- 1- 0

1- A hydroxide ion is formed when a water molecule loses a hydrogen ion.

The unequal sharing of electrons within a water molecule makes the water molecule _____. have a low surface tension change easily from a liquid to gaseous form hydrophobic ionic polar

polar

In this molecule, what type of bond is found between the oxygen and hydrogens? The figure shows the molecular model of a molecule, which consists of two hydrogen atoms connected to an oxygen atom. The oxygen atom has a negative charge. Two hydrogen atoms have positive charges. polar covalent hydrophilic ionic hydrophobic nonpolar covalent

polar covalent

Why doesn't oil mix with water? (a) Nonpolar molecules repel water molecules. (b) Polar molecules repel nonpolar molecules. (c) Polar molecules attract one another. (d) Nonpolar molecules attract one another. Both (a) and (d).

(c) Polar molecules attract one another.

Which of the following helps most to explain why water has a high specific heat? (a) A water molecule can make 4 hydrogen bonds. (b) The water molecule has exceptionally strong covalent bonds. (c) Water temperature is exceptionally sensitive to heat. Both (a) and (b). Both (b) and (c)

(a) A water molecule can make 4 hydrogen bonds.

The open spaces in water's crystal structure make it possible for ... (a) aquatic life to exist at the North Pole. (b) water to have a low boiling point. (c) life to occur in hot springs. Both (b) and (c). (a), (b), and (c).

(a) aquatic life to exist at the North Pole.

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.

(a), (b), and (c) are correct.

Which statement is true of water's tensile strength? (a) It results from hydrogen bonding. (b) It helps to pull water through plants. (c) It involves both cohesion and adhesion. Both (a) and (b). (a), (b), and (c).

(a), (b), and (c).

About _____ molecules in a glass of water are dissociated. 1 in 500,000,000 1 in 1,000,000,000 1 in 1,000,000 1 in 5,000,000 1 in 2

1 in 500,000,000 One in half a billion.

What is the charge on a hydronium ion? 0 1+ 2+ 2- 1-

1+ The formation of hydronium results in the gain of 1 more proton than electron.

How did this molecule form? The figure shows a positively charged molecule. This molecule consists of three hydrogen atoms bonded to an oxygen atom. Evaporation. A hydrogen molecule bonded with an OH- molecule. Two water molecules bonded. A water molecule gained an hydrogen ion from another water molecule. A water molecule split in half.

A water molecule gained an hydrogen ion from another water molecule.

Water is a source of ______________ for chemical reactions in cells. (a) hydrogen atoms (b) oxygen atoms (c) energy Both (a) and (b) (a), (b), and (c).

Both (a) and (b) [ hydrogen atoms, oxygen atoms]

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).

Both (a) and (b).

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).

Both (a) and (b).

Which of these is the correct equation for the dissociation of water? H+<==> H2O + H2O+ H2O + OH-<==> H2O+ H2O <==> H+ + OH- H2O + H2O <==> H3O+ + OH- H2O + H2O+<==> H2O + OH-

H2O + H2O <==> H3O+ + OH- This is the correct equation for the dissociation of water molecules.

Which of these bonds is weakest?

Hydrogen Bonds are weaker than covalent bonds because they do not involve sharing of electrons, and they are weaker than ionic bonds because they involve the attraction of partial (not full) opposite charges.

Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface? Polar groups attract one another. Nonpolar groups attract one another. Polar groups repel water. Nonpolar groups repel water. All of the above.

Polar groups attract one another.

The arrow is indicating a single proton

a hydrogen ion (H+).

Dissolving is best described as ... a separation of molecules into neutral atoms. a change from a solid to a liquid. breaking covalent bonds. molecules breaking into ions. a mingling of molecules and/or ions.

a mingling of molecules and/or ions.

Hydrogen bonds ... share electrons between the two bonded atoms. are covalent bonds. can form between H and N. occur within a water molecule. All of the above.

can form between H and N.

The transfer of a hydrogen atom from one water molecule to another is referred to as

dissociation

The tendency of an atom to pull electrons toward itself is referred to as its _____. ionic potential electronegativity polarity tonicity covalency

electronegativity

What process exerts the pull on water molecules that is relayed from leaf to root via cohesion? precipitation gravity evaporation antigravity

evaporation

Each water molecule is joined to _____ other water molecules by ____ bonds. two ... polar covalent four ... polar covalent two ... hydrogen four ... hydrogen three ... ionic

four ... hydrogen

Water has surface tension because ... molecules at the surface make more hydrogen bonds. hydrogen bonds between surface water molecules resist being stretched. cohesion forces are weaker at the surface. water tends to evaporate from the surface. there is positive pressure inside the water mass.

hydrogen bonds between surface water molecules resist being stretched.

In a neutral solution the concentration of _____. hydrogen ions is less than the concentration of hydroxide ions water molecules is less than the concentration of hydrogen ions water molecules is less than the concentration of hydroxide ions hydrogen ions is greater than the concentration of hydroxide ions hydrogen ions is equal to the concentration of hydroxide ions

hydrogen ions is equal to the concentration of hydroxide ions This is the definition of a neutral solution.

What name is given to this molecule? The figure shows a positively charged molecule. This molecule consists of three hydrogen atoms bonded to an oxygen atom. water hydroxide ion hydronium ion methane glucose

hydronium ion

What name is given to this molecule? The figure shows a negatively charged molecule. This molecule consists of a hydrogen atom bonded to an oxygen atom. glucose DNA water hydronium ion hydroxide ion

hydroxide ion

Why isn't this insect drowning? (Pic is of a bug sitting on the surface of water) It is difficult to change the temperature of water. The insect is swimming. Surface tension. The insect is very light. The insect is flying just above the water surface.

surface tension