BIO 100 MIDTERM EXAM PRACTICE
QUESTIONS AND COMPLETE SOLUTIONS
◉ van der Waals interaction
Answer: a weak attraction or interaction between molecules
caused by slightly positively charged or slightly negatively
charged atoms
◉ Which of the following statements is not true?
Answer: Water is the most abundant atom in Earth's atmosphere.
◉ Using a pH meter, you find the pH of an unknown solution to be
8.0. How would you describe this solution?
Answer: weakly basic
◉ The pH of lemon juice is about 2.0, whereas tomato juice's pH is
about 4.0. Approximately how much of an increase in hydrogen
ion concentration is there between tomato juice and lemon juice?
Answer: 100 times
◉ Why can some insects walk on water?
Answer: Some insects can walk on water, although they are
heavier (denser) than water, because of the surface tension of
water. Surface tension results from cohesion, or the attraction
,between water molecules at the surface of the body of water [the
liquid-air (gas) interface].
◉ Explain why water is an excellent solvent.
Answer: Water molecules are polar, meaning they have separated
partial positive and negative charges. Because of these charges,
water molecules are able to surround charged particles created
when a substance dissociates. The surrounding layer of water
molecules stabilizes the ion and keeps differently charged ions
from reassociating, so the substance stays dissolved.
◉ acid
Answer: a substance that donates hydrogen ions and therefore
lowers pH
◉ Adhesion
Answer: the attraction between water molecules and molecules of
a different substance
◉ base
Answer: a substance that absorbs hydrogen ions and therefore
raises pH
◉ buffer
Answer: a solution that resists a change in pH by absorbing or
releasing hydrogen or hydroxide ions
,◉ cohesion
Answer: the intermolecular forces between water molecules
caused by the polar nature of water; creates surface tension
◉ evaporation
Answer: the release of water molecules from liquid water to form
water vapor
◉ Hydrophilic
Answer: describes a substance that dissolves in water; water-
loving
◉ Hydrophobic
Answer: describes a substance that does not dissolve in water;
water-fearing
◉ litmus paper
Answer: filter paper that has been treated with a natural water-
soluble dye so it can be used as a pH indicator
◉ pH scale
Answer: a scale ranging from 0 to 14 that measures the
approximate concentration of hydrogen ions of a substance
, ◉ Solvant
Answer: a substance capable of dissolving another substance
◉ surface tension
Answer: the cohesive force at the surface of a body of liquid that
prevents the molecules from separating
◉ temperature
Answer: a measure of molecular motion
◉ An example of a monosaccharide is
Answer: fructose, glucose and galactose
◉ Cellulose and starch are examples of
Answer: polysaccharides
◉ Phospholipids are important components of
Answer: the plasma membrane of cells
◉ The monomers that make up proteins are called
Answer: amino acids
◉ Explain at least three functions that lipids serve in plants
and/or animals.
QUESTIONS AND COMPLETE SOLUTIONS
◉ van der Waals interaction
Answer: a weak attraction or interaction between molecules
caused by slightly positively charged or slightly negatively
charged atoms
◉ Which of the following statements is not true?
Answer: Water is the most abundant atom in Earth's atmosphere.
◉ Using a pH meter, you find the pH of an unknown solution to be
8.0. How would you describe this solution?
Answer: weakly basic
◉ The pH of lemon juice is about 2.0, whereas tomato juice's pH is
about 4.0. Approximately how much of an increase in hydrogen
ion concentration is there between tomato juice and lemon juice?
Answer: 100 times
◉ Why can some insects walk on water?
Answer: Some insects can walk on water, although they are
heavier (denser) than water, because of the surface tension of
water. Surface tension results from cohesion, or the attraction
,between water molecules at the surface of the body of water [the
liquid-air (gas) interface].
◉ Explain why water is an excellent solvent.
Answer: Water molecules are polar, meaning they have separated
partial positive and negative charges. Because of these charges,
water molecules are able to surround charged particles created
when a substance dissociates. The surrounding layer of water
molecules stabilizes the ion and keeps differently charged ions
from reassociating, so the substance stays dissolved.
◉ acid
Answer: a substance that donates hydrogen ions and therefore
lowers pH
◉ Adhesion
Answer: the attraction between water molecules and molecules of
a different substance
◉ base
Answer: a substance that absorbs hydrogen ions and therefore
raises pH
◉ buffer
Answer: a solution that resists a change in pH by absorbing or
releasing hydrogen or hydroxide ions
,◉ cohesion
Answer: the intermolecular forces between water molecules
caused by the polar nature of water; creates surface tension
◉ evaporation
Answer: the release of water molecules from liquid water to form
water vapor
◉ Hydrophilic
Answer: describes a substance that dissolves in water; water-
loving
◉ Hydrophobic
Answer: describes a substance that does not dissolve in water;
water-fearing
◉ litmus paper
Answer: filter paper that has been treated with a natural water-
soluble dye so it can be used as a pH indicator
◉ pH scale
Answer: a scale ranging from 0 to 14 that measures the
approximate concentration of hydrogen ions of a substance
, ◉ Solvant
Answer: a substance capable of dissolving another substance
◉ surface tension
Answer: the cohesive force at the surface of a body of liquid that
prevents the molecules from separating
◉ temperature
Answer: a measure of molecular motion
◉ An example of a monosaccharide is
Answer: fructose, glucose and galactose
◉ Cellulose and starch are examples of
Answer: polysaccharides
◉ Phospholipids are important components of
Answer: the plasma membrane of cells
◉ The monomers that make up proteins are called
Answer: amino acids
◉ Explain at least three functions that lipids serve in plants
and/or animals.
