physical science (chemistry)

part 4

chemistry

the study of matter, its properties, and how substances change

matter

anything that has mass and occupies space

mass

the amount of matter in an object

volume

the amount of space an object occupies

density

the amount of mass in a given volume (mass ÷ volume)

physical property

a characteristic that can be observed without changing a substance's identity

chemical property

a characteristic describing a substance's ability to undergo chemical change

physical change

a change in form or state that does not create a new substance

chemical change

a change that produces one or more new substances

pure substance

matter with a fixed chemical composition

element

a pure substance made of only one type of atom

compound

a pure substance made of two or more different elements chemically bonded together

mixture

two or more substances physically combined without chemical bonding between them

solid

a state of matter with a definite shape and volume

liquid

a state of matter with a definite volume but no definite shape

gas

a state of matter with no definite shape or volume

plasma

a state of matter made of charged particles, found in stars and lightning

melting

the change from a solid to a liquid

freezing

the change from a liquid to a solid

vaporization

the change from a liquid to a gas

evaporation

the change from a liquid to a gas at its surface

boiling

rapid vaporization throughout a liquid when its vapor pressure equals the surrounding pressure

condensation

the change from a gas to a liquid

sublimation

the change directly from a solid to a gas

deposition

the change directly from a gas to a solid

melting point

the temperature at which a substance changes from solid to liquid at a given pressure

boiling point

the temperature at which a liquid boils at a given pressure

atom

the smallest unit of an element that retains its chemical identity

nucleus

the dense center of an atom containing protons and neutrons

proton

a positively charged particle found in an atom's nucleus

neutron

an electrically neutral particle found in an atom's nucleus

electron

a negatively charged particle found in the region surrounding an atom's nucleus

atomic number

the number of protons in an atom's nucleus

mass number

the total number of protons and neutrons in an atom's nucleus

atomic mass

the mass of an atom, commonly expressed in atomic mass units

atomic mass unit (amu)

a unit used to measure atomic mass

isotope

an atom of the same element with a different number of neutrons

ion

an atom or group of atoms with a positive or negative electrical charge

cation

a positively charged ion formed by losing electrons

anion

a negatively charged ion formed by gaining electrons

nuetral atom

an atom with equal numbers of protons and electrons

valence electrons

electrons in an atom's outermost occupied shell that participate in bonding

electron shell

a region or energy level where electrons are found around the nucleus

periodic table

a chart organizing chemical elements by increasing atomic number

group

a vertical column of elements with similar chemical properties

period

a horizontal row of elements on the periodic table

transition metals

metallic elements found in groups 3–12 of the periodic table

metal

an element that is generally shiny, malleable, and a good conductor of heat and electricity

nonmetal

an element that generally conducts heat and electricity poorly

metalloid

an element with properties between those of metals and nonmetals

alkali metals

highly reactive metals found in group 1, excluding hydrogen

alkaline earth metals

reactive metals found in group 2

halogens

reactive nonmetals found in group 17

noble gases

generally unreactive gases found in group 18

reactivity

how readily a substance undergoes a chemical reaction

chemical symbol

a one- or two-letter abbreviation representing an element

H

hydrogen — the lightest element and a highly flammable gas

He

helium — a lightweight, generally unreactive noble gas

C

carbon — an element essential to organic compounds and living organisms

N

nitrogen — the most abundant gas in Earth's atmosphere

O

oxygen — a gas necessary for human cellular respiration and many combustion reactions

Ns

sodium — a highly reactive alkali metal

Cl

chlorine — a reactive halogen used in many disinfectants

Fe

iron — a metal commonly used to make steel

Cu

copper — a metal known for conducting electricity

Au

gold — a valuable metal resistant to corrosion

Ag

silver — a metal with excellent electrical conductivity

Hg

mercury — a metal that is liquid at room temperature

K

potassium — a highly reactive alkali metal

Ca

calcium — an element important for bones and teeth

Pb

lead — a dense, toxic metal

Si

silicon — a metalloid widely used in electronics

Al

aluminum — a lightweight metal used in many products

S

sulfur — a yellow nonmetal used in various chemicals

chemical bond

an attractive force that holds atoms or ions together

molecule

a group of two or more atoms held together by chemical bonds

ionic bond

the electrostatic attraction between oppositely charged ions

covalent bond

a chemical bond formed when atoms share electrons

chemical formula

a representation showing the types and numbers of atoms in a substance

subscript

a small number in a chemical formula showing how many atoms of an element are present

ionic compound

a compound made of positively and negatively charged ions

molecular compound

a compound made of molecules containing covalently bonded atoms

diatomic molecule

a molecule consisting of two atoms

H₂O

water — a compound made of two hydrogen atoms and one oxygen atom

CO₂

carbon dioxide — a compound made of one carbon atom and two oxygen atoms

NaCl

sodium chloride — an ionic compound commonly known as table salt

metallic bond

the attraction between positive metal ions and mobile electrons

homogeneous mixture

a mixture with a uniform composition throughout

heterogeneous mixture

a mixture with a nonuniform composition

solution

a homogeneous mixture in which one or more substances are dissolved

solute

the substance that is dissolved in a solution

solvent

the substance that dissolves a solute

solubility

the maximum amount of a solute that can dissolve in a given amount of solvent under specified conditions

concentration

the amount of solute present in a given amount of solution

saturated solution

a solution containing the maximum dissolved solute at a given temperature and pressure

filtration

a separation method that uses a barrier to remove solid particles from a fluid

distillation

a separation method that uses differences in boiling points

chromatography

a separation technique based on substances moving differently through a material

unsaturated solution

a solution that can dissolve additional solute under the same conditions

chemical reaction

a process in which substances change into new substances