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Flashcards in Chapter 2 Deck (63):
1

Acid

Any compound that gives up protons or accepts electrons during a chemical reaction or that releases hydrogen ions when dissolved in water.

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Anion

A negatively charged ion.

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Atomic Number

The number of protons in the nucleus of an atom, giving the atom its identity as the particular chemical element.

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Atomic Weight

The average mass of an element that is based on the relative proportions of all the naturally occurring isotopes..

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Base

Any compound that acquires protons or gives up electrons during a chemical reaction or accepts hydrogen ions when dissolved in water.

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Cation

A positively charged ion.

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Chemical Bond

An attractive force binding two atoms together. Covalent bonds, ionic bonds, and hydrogen bonds are types of chemical bonds.

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Chemical Energy

The potential energy stored in covalent bonds between atoms.

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Chemical Equilibrium

A dynamic but stable state of a reversible chemical reaction in which the forward reaction and reverse reactions proceed at the same rate, so that the concentrations of reactants and products remain constant.

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Chemical Evolution

The theory that simple chemical compounds in the early atmosphere and ocean combined via chemical reactions to form larger, more complex substances, eventually leading to the origin of life and the start of biological evolution.

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Chemical Reaction

Any process in which one compound or element is combined with others or is broken down; involves the making and/or breaking of chemical bonds.

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Cohesion

The tendency of certain like molecules (e.g., water molecules) to cling together due to attractive forces. Compare to adhesion.

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Covalent bond

A type of chemical bond in which two atoms share one or more pairs of electrons. Compare with hydrogen bond and ionic bond.

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Dalton (Da)

A unit of mass equal to 1/12 the mass of one carbon-12 atom; about the mass of 1 proton or 1 neutron.

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Electron shell

A group of orbitals of electrons with similar energies. Electron shells are arranged in roughly concentric layers around the nucleus of an atom, and electrons in outer shells have more energy than those in inner shells. Electrons in the outermost shell, the valence shell, often are involved in chemical bonding.

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Electronegativity

A measure of the ability of an atom to attract electrons toward itself from an atom to which it is bonded.

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Element

A substance, consisting of atoms with a specific number of protons. Elements preserve their identity in chemical reactions.

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Endothermic

Referring to a chemical reaction that absorbs heat. Compare with exothermic.

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Energy

The capacity to do work or to supply heat. May be stored (potential energy) or available in the form of motion (kinetic energy).

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First Law of Thermodynamics

The principle of physics that energy is conserved in any process. Energy can be transferred and converted into different forms, but it cannot be created or destroyed.

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Free radicals

Any substance containing one or more atoms with an unpaired electron. Unstable and highly reactive.

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Functional group

A small group of atoms bonded together in a precise configuration and exhibiting particular chemical properties that it imparts to any organic molecule in which it occurs.

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Heat

Thermal energy that is transferred from an object at higher temperature to one at lower temperature.

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Heat of Vaporization

The energy required to vaporize 1 gram of a liquid into a gas.

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Homeostasis

(adjective: homeostatic) The array of relatively stable chemical and physical conditions in an animal's cells, tissues, and organs. May be achieved by the body's passively matching the conditions of a stable external environment (conformational homeostasis) or by active physiological processes (regulatory homeostasis) triggered by variations in the external or internal environment.

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Hydrogen Bond

A weak interaction between two molecules or different parts of the same molecule resulting from the attraction between a hydrogen atom with a partial positive charge and another atom (usually O or N) with a partial negative charge. Compare with covalent bond and ionic bond.

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Hydrogen ion (H+)

A single proton with a charge of 1+; typically, one that is dissolved in solution or that is being transferred from one atom to another in a chemical reaction.

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Hydrophilic

Interacting readily with water. Hydrophilic compounds are typically polar compounds containing partially or fully charged atoms. Compare with hydrophobic.

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Hydrophobic

Not readily interacting with water. Hydrophobic compounds are typically nonpolar compounds that lack partially or fully charged atoms. Compare with hydrophilic.

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Hydrophobic interactions

Very weak interactions between nonpolar molecules, or nonpolar regions of the same molecule, when exposed to an aqueous solvent. The surrounding water molecules support these interactions by interacting with one another and encapsulating the nonpolar molecules.

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Hydroxide ion (OH-)

An oxygen atom and a hydrogen atom joined by a single covalent bond and carrying a negative charge; formed by dissociation of water.

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Ionic bond

A chemical bond that is formed when an electron is completely transferred from one atom to another so that the atoms remain associated due to their opposite electric charges. Compare with covalent bond and hydrogen bond.

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Isotope

Any of several forms of an element that have the same number of protons but differ in the number of neutrons.

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Mass number

The total number of protons and neutrons in an atom.

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Molarity

A common unit of solute concentration equal to the number of moles of a dissolved solute in 1 liter of solution.

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Mole

The amount of a substance that contains 6.022 * 1023 of its elemental entities (e.g., atoms, ions, or molecules). This number of molecules of a compound will have a mass equal to the molecular weight of that compound expressed in grams.

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Molecular formula

A notation that indicates only the numbers and types of atoms in a molecule, such as H2O for the water molecule. Compare with structural formula.

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Molecular weight

The sum of the atomic weights of all of the atoms in a molecule; roughly, the total number of protons and neutrons in the molecule.

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Molecule

A combination of two or more atoms held together by covalent bonds.

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Nonpolar covalent bond

A covalent bond in which electrons are equally shared between two atoms of the same or similar electronegativity. Compare with polar covalent bond.

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Orbital

The region of space around an atomic nucleus in which an electron is present most of the time.

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Organic

For a compound, containing carbon and hydrogen and usually containing carbon–carbon bonds. Organic compounds are widely used by living organisms.

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Photon

A discrete packet of light energy; a particle of light.

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Polar covalent bond

A covalent bond in which electrons are shared unequally between atoms differing in electronegativity, resulting in the more electronegative atom having a partial negative charge and the other atom, a partial positive charge. Compare with nonpolar covalent bond.

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Potential energy

Energy stored in matter as a result of its position or molecular arrangement. Compare with kinetic energy.

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Prebiotic soup model

Hypothetical explanation for chemical evolution whereby small molecules reacted with one another in a mixture of organic molecules condensed into a body of water, typically in reference to the early oceans.

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Product

Any of the final materials formed in a chemical reaction.

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Radioactive isotope

A version of an element that has an unstable nucleus, which will release radiation energy as it decays to a more stable form. Decay often results in the radioisotope becoming a different element.

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Reactant

Any of the starting materials in a chemical reaction.

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Solute

Any substance that is dissolved in a liquid.

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Solution

A liquid containing one or more dissolved solids or gases in a homogeneous mixture.

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Solvent

Any liquid in which one or more solids or gases can dissolve.

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Space-filling model

A representation of a molecule where atoms are shown as balls—color-coded and scaled to indicate the atom's identify—attached to each other in the correct geometry.

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Specific heat

The amount of energy required to raise the temperature of 1 gram of a substance by 1°C; a measure of the capacity of a substance to absorb energy.

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Structural formula

A two-dimensional notation in which the chemical symbols for the constituent atoms are joined by straight lines representing single (–), double (=), or triple (=) covalent bonds. Compare with molecular formula.

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Surface metabolism model

Hypothetical explanation for chemical evolution whereby small molecules reacted with one another through catalytic activity associated with a surface, such as the mineral deposits found in deep-sea hydrothermal vents.

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Surface tension

The cohesive force that causes molecules at the surface of a liquid to stick together, thereby resisting deformation of the liquid's surface and minimizing its surface area.

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System

A defined set of interacting chemical components under observation.

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Temperature

A measurement of thermal energy present in an object or substance, reflecting how much the constituent molecules are moving.

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Thermal energy

The kinetic energy of molecular motion.

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Valence

The number of unpaired electrons in the outermost electron shell of an atom; often determines how many covalent bonds the atom can form.

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Valence electron

An electron in the outermost electron shell, the valence shell, of an atom. Valence electrons tend to be involved in chemical bonding.

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Valence shell

The outermost electron shell of an atom.