Chapter 2: A Chemistry Comes Alive - Vocabulary Flashcards

Vocabulary flashcards covering key terms from Chapter 2: matter, energy, atoms/elements, bonding, and chemical reactions.

Matter

Anything that has mass and occupies space.

Energy

The capacity to do work or put matter into motion; it has no mass and takes up no space.

Kinetic energy

Energy in action.

Potential energy

Stored (inactive) energy.

Chemical energy

Stored in the bonds of chemical substances.

Electrical energy

Results from the movement of charged particles.

Mechanical energy

Energy directly involved in moving matter.

Radiant energy

Energy that travels in waves (heat, visible light, X rays, etc.).

Solid

State of matter with a definite shape and volume.

Liquid

State of matter with a changeable shape and definite volume.

Gas

State of matter with a changeable shape and volume.

Atom

The basic unit of matter, composed of protons, neutrons, and electrons.

Element

A substance that cannot be broken down into simpler substances by ordinary chemical methods.

Carbon

One of the four elements that make up about 96% of the human body.

Oxygen

One of the four elements that make up about 96% of the human body.

Hydrogen

One of the four elements that make up about 96% of the human body.

Nitrogen

One of the four elements that make up about 96% of the human body.

Periodic table

A table that lists all known chemical elements.

Proton

Positively charged subatomic particle in the nucleus; about 1 amu.

Neutron

Electrically neutral subatomic particle in the nucleus; about 1 amu.

Electron

Negatively charged subatomic particle that orbits the nucleus; very small mass.

Nucleus

Center of the atom that contains protons and neutrons.

Electron shell

Energy levels around the nucleus where electrons reside; can be several shells.

Valence shell

Outermost electron shell; contains electrons involved in bonding.

Octet rule

Atoms tend to have 8 electrons in their valence shell (2 for H and He).

Isotope

Structural variations of an element with the same atomic number but different mass numbers.

Atomic number

Number of protons in the nucleus; identifies the element.

Mass number

Total number of protons and neutrons in the nucleus.

Atomic weight

Average mass numbers of all isotope forms of an element.

Ion

Atom that has gained or lost electrons and becomes electrically charged.

Cation

Positively charged ion (lost electrons).

Anion

Negatively charged ion (gained electrons).

Ionic bond

Bond formed by transfer of electrons between atoms; attraction between opposite charges.

Salt

Most ionic compounds; when dry, they form crystals (e.g., NaCl).

Covalent bond

Bond formed by sharing electrons between atoms.

Polar covalent bond

Unequal sharing of electrons; results in polar molecules (dipole).

Nonpolar covalent bond

Equal sharing of electrons; electrically balanced.

Hydrogen bond

Weak attraction between a hydrogen in one molecule and an electronegative atom in another; important in water.

Molecule

Two or more atoms bonded together.

Compound

A molecule that contains two or more different kinds of atoms.

Reactants

Substances entering into a chemical reaction.

Products

Substances produced by a chemical reaction.

Chemical reaction

Process in which bonds are formed, rearranged, or broken.

Synthesis

Reaction where smaller units combine to form a larger, more complex molecule.

Decomposition

Reaction where a molecule is broken down into smaller molecules or atoms.

Exchange (displacement) reaction

Reaction involving both synthesis and decomposition where parts are exchanged.

Redox (oxidation-reduction)

Reactions involving transfer of electrons; oxidation is loss, reduction is gain.

Exergonic

Reactions that release energy.

Endergonic

Reactions that absorb energy.

Equilibrium

State where forward and reverse reactions are balanced; reversible in theory.