Chapter 2: Chemistry of Life

Fill-in-the-blank flashcards covering key terms and concepts from Chapter 2: Chemistry of Life.

Matter consists of chemical elements in pure form and in combinations called __.

compounds

An element that cannot be broken down to other substances by chemical reactions is called an __.

element

A substance consisting of two or more different elements combined in a fixed ratio is a __.

compound

The four elements that make up about 96% of all living matter are oxygen, carbon, hydrogen, and __.

nitrogen

Some trace elements such as __ are required by all forms of life.

iron (Fe)

The atomic number of helium is __.

2

The atomic mass of helium is __.

4

A subatomic particle that is electrically neutral is a __.

neutron

A subatomic particle with one unit of positive charge is a __.

proton

A subatomic particle with one unit of negative charge is an __.

electron

The atomic number indicates the number of __ in the nucleus.

protons

Atomic mass is an approximation of the total mass of an atom, measured in __.

Daltons

Isotopes are different atomic formations of the same element, having more __ than other atoms of the same element.

neutrons

Electron shells: Represented as concentric circles in diagrams, electron shells represent the __ distance from the nucleus and energy level of electrons circling the nucleus.

average

The number of electrons in the outermost shell is called the __.

valence electrons

For carbon (atomic number 6), the number of electrons is __.

6

Carbon has isotopes: 12C, 13C, and __.

14C

A radioactive isotope is one in which the nucleus decays spontaneously; one medical application is __ tracers.

radioactive

The only subatomic particle directly involved in chemical reactions between atoms is the __.

electron

In photosynthesis, the movement of electrons centers on the processes of photosynthesis and __.

cellular respiration

Potential energy is energy that matter possesses because of its __.

location

The number of electrons in the outermost shell is called the __.

valence electrons

Sodium has __ valence electron(s).

1

Water's molecular formula is __.

H2O

The ratio of hydrogen to oxygen in water is __.

2:1

Electronegativity is the attraction of an atom for the electrons of a covalent bond.

electronegativity

Nonpolar covalent bonds occur when electrons are shared __ between atoms.

equally

Polar covalent bonds occur when one atom is bonded to a more __ atom.

electronegative

Oxygen is more __ than hydrogen, making water a polar molecule.

electronegative

In NaCl, sodium becomes a and chlorine becomes a .

cation; anion

A hydrogen bond is a weak attraction between the partial positive charge on a hydrogen and the partial negative charge on __ of another molecule.

oxygen

Van der Waals interactions are very weak attractions that occur when atoms and molecules are very __ together.

close

Morphine mimics endorphins by binding to endorphin __ in the brain.

receptors

Chemical bonds store __ energy and release energy when broken.

potential

In the photosynthesis equation, one product is __.

O2

CO2 + H2O -> C6H12O6 + __; the blank is the __.

O2

In the photosynthesis equation, CO2 and H2O are the __.

reactants

NAD+ accepts electrons to form __.

NADH

Electrons have more potential energy when they are associated with __ electronegative atoms.

less

The most electronegative element is __.

oxygen

Cohesion is the phenomenon of water molecules sticking to each other; adhesion is the clinging of water to another __.

substance

The dissolving agent of a solution is the __.

solvent

A solution is a completely __ mixture of two or more substances.

homogeneous

A substance dissolved by the solvent is the __.

solute

An aqueous solution is a solution in which water is the __.

solvent

In coffee with sugar, the solvent is and the solute is .

coffee; sugar

Water is a good solvent due to its __.

polarity

Hydrophilic substances have an affinity for water; hydrophobic substances repel water. Cotton is a substance, while vegetable oil is a substance.

hydrophilic; hydrophobic

pH is defined as the negative log of the hydrogen ion concentration, [H+], which is measured in __.

M (moles per liter)

Water dissociates into hydronium (H3O+) and __.

OH-

The product [H+][OH-] is equal to __ at 25°C.

1e-14

A buffer minimizes changes in pH by using a weak acid and its conjugate __.

base

CO2 emissions cause ocean acidification by forming carbonic acid, which lowers the ocean's __.

pH

Cohesion is the phenomenon of water molecules sticking to each other; adhesion is the clinging of water to another __.

substance

The calorie is the amount of heat it takes to raise the temperature of 1 g of water by __ degree Celsius.

1

Water's specific heat is cal/(g·°C); alcohol's is cal/(g·°C).

1; 0.6

Evaporation is the transformation of a liquid to a __.

gas

The heat of vaporization is the amount of heat required to convert 1 g of a liquid to a __.

gas

Ice floats because ice is less dense than water; at 4°C water has a maximum __.

density