Once labor begins in childbirth, contractions increase in intensity and frequency until delivery. The increasing labor contractions of childbirth are an example of which type of regulation?
positive feedback
In comparing covalent bonds and ionic bonds, which of the following would you expect?
Covalent bonds and ionic bonds occupy opposite ends of a continuous spectrum, from nearly equal to completely unequal sharing of electrons
What is the maximum number of hydrogen atoms that can be covalently bonded in a molecule containing two carbon atoms?
6
Which statement is true of all atoms that are anions?
The atom has more electrons than protons.
When two atoms are equally electronegative, they will interact to form
nonpolar covalent bonds
In what way are elements in the same column of the periodic table the same?
They have the same number of electrons in their valence shell.
A water sample from a hot thermal vent contained a single-celled organism that had a cell wall but lacked a nucleus. What is its most likely classification?
Archaea
What results from an unequal sharing of electrons between atoms?
a polar covalent bond
What is the difference between covalent bonds and ionic bonds?
Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the electrical attraction between atoms.
A covalent bond is likely to be polar when
one of the atoms sharing electrons is much more electronegative than the other atom.
In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by
polar covalent bonds.
Why does ice float in liquid water?
Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water.
Based on your knowledge of the polarity of water molecules, the solute molecule depicted here is most likely
positively charged.
Which of the following is a hydrophobic material?
wax
Water molecules are able to form hydrogen bonds with
compounds that have polar covalent bonds.
Which of the following solutions would require the greatest amount of base to be added to bring the solution to neutral pH?
gastric juice at pH 2
Increased atmospheric CO2 concentrations might have what effect on seawater?
Seawater will become more acidic, and carbonate concentrations will decrease.
The bonds that are broken when water vaporizes are
hydrogen bonds between water molecules.
The partial negative charge in a molecule of water occurs because
the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus.
Sulfur is in the same column of the periodic table as oxygen, but has electronegativity similar to carbon. Compared to water molecules, molecules of H2S
will not form hydrogen bonds with each other.
A covalent chemical bond is one in which
outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms.
Which of the following would be regarded as compounds?
H2O and CH4, but not O2
The atomic number of nitrogen is 7. Nitrogen-15 is heavier than nitrogen-14 because the atomic nucleus of nitrogen-15 contains how many neutrons?
8
Protists and bacteria are grouped into different domains because
protists have a membrane-bounded nucleus, which bacterial cells lack.
Which bond or interaction would be difficult to disrupt when compounds are put into water?
covalent bond
One difference between carbon-12 () is that carbon-14 () has
two more neutrons than carbon-12
The main source of energy for producers in an ecosystem is
Light
A 0.01 M solution of a substance has a pH of 2. What can you conclude about this substance?
It is a strong acid that ionizes completely in water
You have two beakers. One contains a solution of HCl at pH = 1.0. The other contains a solution of NaOH at pH = 13. Into a third beaker, you slowly and cautiously pour 20 mL of the HCl and 20 mL of the NaOH. After complete stirring, the pH of the mixture will be
7.0
Which of the following takes place as an ice cube cools a drink?
Kinetic energy in the drink decreases
Why does evaporation of water from a surface cause cooling of the surface?
The water molecules with the most heat energy evaporate more readily.
Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon?
the release of heat by the formation of hydrogen bonds
Which type of bond must be broken for water to vaporize?
hydrogen bonds
Liquid water's high specific heat is mainly a consequence of the
absorption and release of heat when hydrogen bonds break and form.
In what way are elements in the same column of the periodic table the same?
They have the same number of electrons in their valence shell.
Prokaryotes are classified as belonging to two different domains. What are the domains?
Bacteria and Archaea
In the term trace element, the modifier trace means that
the element is required in very small amounts.
Why is each element unique and different from other elements in chemical properties?
Each element has a unique number of protons in its nucleus.
About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter?
carbon, hydrogen, nitrogen, oxygen
Which of the following is not considered to be a weak molecular interaction?
a covalent bond
Compared with 31P, the radioactive isotope 32P has
one more neutron.
Which of the following effects is produced by the high surface tension of water?
A water strider can walk across the surface of a small pond.
Which of the following is a hydrophobic material?
wax
The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called?
a hydrogen bond
Which of the following are qualities of any good scientific
hypothesis?
I. It is testable.
II. It is
falsifiable.
III. It produces quantitative data.
IV. It
produces results that can be replicated.
I and II
Which of the following explains most specifically the attraction of water molecules to one another?
hydrogen bond
Nitrogen (N) is much more electronegative than hydrogen (H). Which of the following statements is correct about the atoms in ammonia (NH3)?
Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge.
Which of these individuals is likely to be most successful in an evolutionary sense?
an organism that dies after five days of life but leaves 10 offspring, all of whom survive to reproduce
Hydrophobic substances such as vegetable oil are
nonpolar substances that repel water molecules.
When the body's blood glucose level rises, the pancreas secretes insulin and, as a result, the blood glucose level declines. When the blood glucose level is low, the pancreas secretes glucagon and, as a result, the blood glucose level rises. Such regulation of the blood glucose level is the result of
negative feedback.