Chapter 2: The Chemical Basis of Life I QUESTIONS
Which of the following is the best description of the modern model of atomic structure?
A central nucleus surrounded by cloudlike orbitals containing electrons.
Polar covalent bond
A covalent bond in which the atoms share electrons unequally
Which of the following contributes to water's stability in a liquid state?
A high heat of fusion A high heat of vaporization
Ionic bond
Bond between a cation and an anion
Hydrogen bond
Bond between atoms with partial positive and partial negative charges
neutral pH
Contains equal numbers of OH- and H+ ions
Atomic mass is measured in units of
Da (Daltons).
Which best describes a contemporary model of electron movement within atoms?
Electrons move in orbitals, although their exact location cannot be precisely predicted in these orbitals.
When water ionizes, it produces what ions?
H+ OH-
Select all of the following molecules that are predicted to easily dissolve in water.
Ions that carry full electric charges. Carbohydrates that contain -OH groups.
Which of the following is a trace element that plays an important role in the transport of oxygen in the blood of many animals?
Iron
Which of the following statements are true of a polar covalent bond?
The atoms in the bond differ in electronegativity. The two atoms in the bond share the electrons unequally.
Energy
The capacity to affect change or do work.
Compared with liquid water, ice has
a more orderly arrangement of water molecules. more hydrogen bonds between individual water molecules.
A Na+ ion forms when
a sodium atom loses an electron.
A substance that releases hydrogen ions into solution is called a(n)
acid
If you add H+ ions to a solution, it becomes more
acidic
The property of water that refers to its ability to be attracted to and adhere to a surface that is not electrically neutral is
adhesion
The hydrogen bonds between water molecules form between
an oxygen atom on one water molecule and a hydrogen atom on a second water molecule.
In living organisms, most chemical reactions take place in ______ solutions.
aqueous
Molecules with covalent bonds
are flexible within certain limits.
The fundamental unit of matter is the
atom
A substance that absorbs hydrogen ions in solution is called a(n)
base
nonpolar covalent bond
bond in which two atoms share electrons equally
polar covalent bond
bond in which two atoms share electrons unequally
Hydrolysis reactions
break apart molecules via water.
What type(s) of compound(s) minimize pH fluctuations in the fluids of living organisms?
buffer buffering agent
Living organisms minimize changes in their internal pH using compounds called
buffers
Chemical reactions require a source of energy and also may require a substance called a(n) ____________ that speeds up the reaction rate. Most chemical reactions proceed toward a state called ______________ in which the rate of product formation equals the rate of reactant formation.
catalyst, equilibrium
The movement of water through the vessels in a plant is aided by the property of water called
cohesion
The amount of solute (in grams) dissolved in a given volume of solution is the solution's
concentration
Structural formulas depict molecules with what type of bonds?
covalent
One ______ equals one 12th the mass of a carbon atom.
dalton
Because exercise produces lactic acid, it may
decrease the pH of body fluids.
High specific heat, surface tension, and cohesion are several properties of water involving __________ bonds
hydrogen
Hydrochloric acid is considered an acid because it releases ___________ ions into solution.
hydrogen
What type of bond is indicated by a dotted line?
hydrogen bond
In a _________ reaction, water is used to break apart another molecule.
hydrolysis
Within an atom's structure, electrons can be found
in cloud-like orbitals.
Electronegativity differences between atoms dictate the polarity of molecules by
influencing whether covalent bonds are polar or nonpolar.
An atom with a net electric charge is called a(n)
ion
The following molecules are likely to dissolve easily in water if they contain which type(s) of bonds?
ionic bonds polar covalent bonds
acid rain can _________ the pH of water entering the roots of plants.
lower
An element's atomic ______ is based on the protons and neutrons it contains, while an element's atomic ______ is based only on the number of protons.
mass; number
When mixed with water, amphipathic molecules may aggregate into spheres called
micelle
The number of moles of a solute dissolved in one liter of solution is the solution's
molarity
The sum of the atomic masses of all atoms in a molecule is equal to the molecule's __________ mass
molecular
pH is defined as the ______ __________ to the base 10 of the _________ ion concentration.
negative logarithm, H+
Isotopes of an element differ from one another in the number of ___ they contain.
neutrons
What part of an amphipathic molecule would be oriented toward the center of a micelle?
nonpolar region
Colligative properties depend on the ______ dissolved in a solution.
number of particles
How many types of atoms can be found in a single element?
only one
Pure water can ionize into
positively charged protons (H+) and negatively charged hydroxide (OH-) ions.
In a water molecule (H2O), each hydrogen atom has a partial ____ charge, and the oxygen atom has a partial __________ charge.
postive, negative
Atoms of different chemical elements can be differentiated based on the number of
protons in the nucleus.
Within an atom, ____ and neutrons have nearly equal masses, while ____ have a much smaller mass.
protons, electrons
Solutes dissolved in a solvent form a(n)
solution
A liquid that can dissolve substances is known as a(n)
solvent
The attraction between molecules at the surface of a liquid is called
surface tension
What happens to the pH of a solution when H+ ions are added to it?
the pH decreases
Cohesion of water is defined as
the property of water molecules attracting each other.
The molecular mass of a molecule is equal to
the sum of the atomic masses of all atoms in the molecule.
All living organisms require ______ elements. These elements are present in extremely small quantities but are still essential for normal growth and function.
trace
A single orbital can contain a maximum of _____ electrons.
two
Electrons in an atom's outermost energy shells are called ______ electrons.
valence
Unpaired ____ electrons enable chemical bonds to form among atoms.
valence
Even though it requires energy to change a liquid to a gas, some water molecules break their hydrogen bonds at ordinary temperatures by
vibrating at higher energy
About 60-70 % of human body weight is composed of ___________ which is a vital component of living organisms.
water
An aqueous solution is one in which the solvent is
water
Most chemical reactions in living organisms involve reactants and products that are dissolved in
water
Which of the following changes in the physical state of water require the input of energy?
Changing from solid to liquid Changing from liquid to gas
Polar covalent O-H bonds in water molecules enable hydrogen bonds to form between water molecules. Which of the following properties of water result from hydrogen bond formation?
Cohesion High specific heat High heat of vaporization Adhesion Surface tension
acidic
Contains more H+ than OH- ions
alkaline
Contains more OH- than H+ ions
A base will absorb _______ ions in solution
Hydrogen
heat of vaporization
The heat energy required to convert 1 mole of a substance from liquid to gas
specific heat
The heat energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius
heat capacity
The heat energy required to raise the temperature of an entire object
heat of fusion
The heat energy that must be withdrawn or released from a substance to convert it from liquid to solid
What is the molarity of a solution?
The number of moles of solute in 1 L
Matter is composed of functional units called _____ two or more of which bonded together form a(n) _____.
atoms, molecule
Electronegativity is the ability of an atom to
attract electrons
The phenomenon of water molecules attracting each other is called
cohesion
If an atom gains or loses a(n) ________ it acquires a net electrical charge and becomes an ion.
electron
What is a likely predictor of how many covalent bonds an atom can form?
electron configuration in the outermost shell
The _____ of an atom is a measure of its ability to attract electrons when in a bond with another atom.
electronegativity
The stability of atoms is greatest when their outer shells are filled with
electrons
_______ which is the vaporization of water, helps animals to dissipate body heat.
evaporation
In ice, H2O molecules move ______ slowly than in water, and consequently hydrogen bonds are broken ______ frequently.
more, less
According to the ____ rule, atoms tend to be most stable when their outer shells are filled; this can be accomplished by gaining, losing, or sharing _____.
octet, electrons
The region of space in which there is a high probability of finding an electron is called a(n):
orbital
The polar groups of a micelle are oriented toward the ______, while its nonpolar groups are oriented toward the _______.
outside, inside
A(n) ______ bond is formed when two atoms of different electronegativities share electrons.
polar covalent
In a micelle, which portion of the amphipathic molecules are oriented toward the surface of the sphere?
polar region
The nucleus of an atom has a net ______ charge.
positive
What are the three subatomic particles?
protons, neutrons, electrons
Which of the following are considered subatomic particles?
protons, neutrons, electrons
To freeze water, energy is
released
structural formulas
represent covalent bonds by a line indicating a pair of electrons.
An electron _____ contains one or more electron orbitals
shell
The concentration of a liquid is defined as the amount of ______ dissolved in a unit volume of solution.
solute
Substances dissolved in liquid are known as
solutes