Why is Water Special?
Is a water molecule polar or nonpolar?
Polar
Which property of water allows a water strider insect to walk across the surface of a pond?
Surface tension/Cohesion
Are table salt (NaCl) and glucose hydrophilic or hydrophobic?
hydrophilic
If you dissolve 10 g of sugar in water, is the sugar the solute or the solvent?
Solute
Classify solutions with a pH of 1, 7, and 12 as acidic, basic, or neutral.
pH 1 = Acidic
pH 7 = Neutral
pH 12 = Basic
In water (H20), what kind of bond is formed between the two hydrogen atoms and the single oxygen atom within the compound?
hydrogen bonds
Match this property to its biological consequence: "Ice is less dense than liquid water"
A. lake freezes from the top down
B. many biological reactions occur in aqueous environments
C. water molecules stick together
D. organisms resist rapid temperature change
Lake freezes from the top down
If you shake oil and water together, what happens after several minutes and why?
They separate because oil is hydrophobic/nonpolar and cannot form hydrogen bonds with water
Identify the solute and the solvent when oxygen is dissolved in blood.
Solute = Oxygen, Solvent = Blood/Water
How many times more acidic is a solution with pH 3 than one with pH 5?
100x more acidic
Why are electrons shared unequally between the oxygen and hydrogen atoms in a water molecule?
Oxygen is more electronegative/attracts shared electrons more strongly
Why do coastal cities typically experience smaller temperature fluctuations than inland cities?
Water's high specific heat / ability to resist rapid temperature changes
Why is having a hydrophilic head and a hydrophobic tail useful for cell membrane phospholipids?
It allows membranes to form barriers between aqueous internal and external cell environments
Define the term solute, solvent, solution
Solute: substance being dissolved
Solvent: the dissolving agent
Solution: homogeneous mixture of two or more substances
Human blood is maintained near pH 7.4. Why might even a small change in blood pH be dangerous to an organism?
It disrupts chemical reactions, protein/enzyme structures, and biological functions
Within a single water molecule, what specific type of bond connects the oxygen atom to the two hydrogen atoms?
Polar covalent bonds
Which of the following types of bond is broken when water evaporates?
A) nonpolar covalent bonds
B) ionic bonds
C) hydrogen bonds
D) polar covalent bonds
hydrogen bonds
Hydrophobic compounds are held together by what type of bonds?
A) Ionic bonds
B) Hydrogen bonds
C) Polar covalent bonds
D) Non-polar covalent bonds
D) Non-polar covalent bonds
Which of the following elements is most likely to form a cation with a charge of +1?
A) Na
B) Cl
C) C
D) O
A) Na
What is the concentration of hydrogen ions [H+] in a solution of pH 5?
A) 10 e-9 M
B) 10 e-5 M
C) 10 e-12 M
D) 10 e-10 M
B) 10 e-5 M
The partial negative charge in a molecule of water occurs because ________.
A) the oxygen atom donates an electron to each of the hydrogen atoms
B) the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus
C) the oxygen atom has two pairs of electrons in its valence shell that are not neutralized by hydrogen atoms
D) one of the hydrogen atoms donates an electron to the oxygen atom
B) The electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus
Which answer best describes why ice floats in liquid water?
A) The high surface tension of liquid water keeps the ice on top.
B) The ionic bonds between the molecules in ice prevent the ice from sinking.
C) Stable hydrogen bonds keep water molecules of ice farther apart than water molecules of liquid water.
D) The crystalline lattice of ice causes it to be denser than liquid water.
C) Stable hydrogen bonds keep water molecules of ice farther apart than water molecules of liquid water
A salamander relies on hydrogen bonding to stick to various surfaces. Therefore, a salamander would have the greatest difficulty clinging to a ________.
A) slightly damp surface
B) surface of hydrocarbons
C) surface of mostly carbon-oxygen bonds
D) surface of mostly carbon-nitrogen bonds
B) surface of hydrocarbons
Neutrally charged atoms have no electric charge because they have ________.
A) uncharged neutrons in their nuclei
B) an equal number of protons and neutrons
C) an equal number of protons and electrons
D) an equal number of charged and uncharged subatomic particles
C) an equal number of protons and electrons
When carbon dioxide in the atmosphere dissolves with the raindrops, what is the expected change in pH of the raindrops?
A) slightly acidic
B) slightly basic
C) same as pure water
D) depends on the altitude where rain drops are formed
A) Slightly acidic