CHEM 1127Q (UConn) - Exam #1

Chemistry

The study of the composition, properties, and interactions of matter

Hypothesis

A tentative explanation of observations that acts as a guide for gathering and checking information

Laws

Summarize a vast number of experimental observations, and describe or predict some facet of the natural world

Theories

Well-sustained, comprehensive, testable explanations of particular aspects of nature; accepted because they provide satisfactory explanations but can be modified if new data becomes available

Scientific Method

The path of discovery that leads from question and observation to law or hypothesis to theory, combined with experimental verification of the hypothesis and any necessary modification of the theory

Macroscopic Domain

Familiar to us; the realm of everyday things that are large enough to be sensed directly by human sight or touch (ex. food you eat, feeling a breeze on your face)

Microscopic Domain

Almost always visited in the imagination; some aspects are visible through a microscope (ex. bacteria); others are too small to be seen even with a microscope (ex. atoms) and must be pictured in the mind

Symbolic Domain

Contains specialized language used to represent components of the macroscopic and microscopic domains; (ex. chemical symbols, chemical formulas, and chemical equations)

Matter

Anything that occupies space and has mass

Solid

Rigid and possesses a definite shape

Liquid

Flows and takes shape of container, except that it forms a flat or slightly curved upper surface when acted upon by gravity

Gas

Takes both the shape and volume of its container

Plasma

A gaseous state of matter that contains appreciable numbers of electrically charged particles; found in high-temperature environments

Mass

A measure of the amount of matter in an object

Weight

The force that gravity exerts on an object; directly proportional to the mass of the object

Law of Conservation of Matter

There is no detectable change in the total quantity of matter present when matter converts from one type to another (a chemical change) or changes among solid, liquid, or gaseous states (a physical change)

Atom

The smallest particle of an element that has the properties of that element and can enter into a chemical combination

Molecule

Consists of two or more atoms joined by strong forces called chemical bonds

Pure Substance

Has a constant composition; all specimens of the substance have the same makeup and properties; divided into two categories: elements and compounds

Elements

Pure substances that cannot be broken down into simpler substances by chemical changes

Accuracy

How closely a measurement aligns with a correct value

Celsius

Unit of temperature; water freezes at 0 and boils at 100 on this scale

Chemical Change

Change producing a different kind of matter from the original kind of matter

Chemical Property

Behavior that is related to the change of one kind of matter into another kind of matter

Compound

Pure substance that can be decomposed into two or more elements

Cubic Centimeter (cm3 or cc)

Volume of a cube with an edge length of exactly 1 cm

Cubic Meter (m3)

SI unit of volume

Density

Ratio of mass to volume for a substance or object

Dimensional Analysis (Factor-Label Method)

Versatile mathematical approach that can be applied to computations ranging from simple unit conversions to more complex, multi-step calculations involving several different quantities

Exact Number

Number derived by counting or by definition

Extensive Property

Property of a substance that depends on the amount of the substance (ex. size, weight, mass)

Fahrenheit

Unit of temperature; water freezes at 32 and boils at 212 on this scale

Heterogeneous Mixture

Combination of substances with a composition that varies from point to point

Homogeneous Mixture (Solution)

Combination of substances with a composition that is uniform throughout

Intensive Property

Property of a substance that is independent of the amount of the substance (ex. color, boiling point, density)

Kelvin (K)

Si unit of temperature; 273.15 K = 0 C

Kilogram (kg)

Standard SI unit of mass; 1 kg = approximately 2.2 lbs

Length

Measure of one dimension of an object

Liter (L) (Cubic Decimeter)

Unit of volume; 1 L = 1000 cm3

Meter (m)

Standard metric and SI unit of length; 1 m = approximately 1.094 yards

Milliliter (mL)

1/1000 of a liter; equal to 1 cm3

Mixture

Matter that can be separated into components by physical means

Molecule

Bonded collection of two or more atoms of the same or different elements

Physical Change

Change in the state or properties of matter that does not involve a change in its chemical composition

Physical Property

Characteristic of matter that is not associated with any change in its chemical composition

Precision

How closely a measurement matches the same measurement when repeated

Rounding

Procedure used to ensure that calculated results properly reflect the uncertainty in the measurements used in the calculation

Second (s)

SI unit of time

SI Units (International System of Units)

Standards fixed by international agreement in the International System of Units

Significant Figures

All of the measured digits in a determination, including the uncertain last digit

Uncertainty

Estimate of amount by which measurement differs from true value

Unit

Standard of comparison for measurements

Unit Conversion Factor

Ratio of equivalent quantities expressed with different units; used to convert from one unit to a different unit

Volume

Amount of space occupied by an object

Actinide

Inner transition metal in the bottom of the bottom two rows of the Periodic Table

Alkali Metal

Element in group 1

Alkaline Earth Metal

Element in group 2

Alpha Particle

Positively charged particle consisting of two protons and two neutrons

Anion

Negatively charged atom or molecule (contains more electrons than protons)

Atomic Mass

Average mass of atoms of an element, expressed in amu

Atomic Mass Unit (amu)

Unit of mass equal to 1/12 of the mass of a 12C atom

Atomic Number (Z)

Number of protons in the nucleus of an atom

Binary Acid

Compound that contains hydrogen and one other element, bonded in a way that imparts acidic properties to the compound (ability to release H+ ions when dissolved in water)

Binary Compound

Compound containing two different elements

Cation

Positively charged atom or molecule (contains fewer electrons than protons)

Chalcogen

Element in group 16

Chemical Symbol

One-, two-, or three-letter abbreviation used to represent an element or its atoms

Covalent Bond

Attractive force between the nuclei of a molecule's atoms and pairs of electrons between the atoms

Covalent Compound

(also called Molecular Compound); Composed of molecules formed by atoms of two or more different elements

Dalton (Da)

Alternative unit equivalent to the atomic mass unit

Dalton's Atomic Theory

Set of postulates that established the fundamental properties of atoms

Electron

Negatively charged, subatomic particle of relatively low mass located outside the nucleus

Empirical Formula

Formula showing the composition of a compound given as the simplest whole-number ratio of atoms

Fundamental Unit of Charge

(also called the elementary charge); Equals the magnitude of the charge of an electron (e) with e=1.602 x 10^(-19) C

Group

Vertical column of the Periodic Table

Halogen

Element in group 17

Inert Gas (Noble Gas)

Element in group 18

Inner Transition Metal (Lanthanide or Actinide)

Element in the bottom two rows; if in the first row, also called lanthanide, or if in the second row, also called actinide

Ion

Electrically charged atom or molecule (contains unequal numbers of protons and electrons)

Ionic Bond

Electrostatic forces of attraction between the oppositely charged ions of an ionic compound

Ionic Compound

Compound composed of cations and anions combined in ratios, yielding an electrically neutral substance

Isomers

Compounds with the same chemical formula but different structures

Isotopes

Atoms that contain the same number of protons but different numbers of neutrons

Lanthanide

Inner transition metal in the top of the bottom two rows of the periodic table

Law of Constant Composition (Law of Definite Proportions)

All samples of a pure compound contain the same elements in the same proportions by mass

Law of Multiple Proportions

When two elements react to form more than one compound, a fixed mass of one element will react with masses of the other element in a ratio of small whole numbers

Main-Group Element (Representative Element)

Elements in columns 1,2, and 12-18

Mass Number (A)

Sum of the number of neutrons and protons in the nucleus of an atom

Metal

Element that is shiny, malleable, good conductor of heat and electricity

MEtalloid

Element that conducts heat and electricity moderately well, and possesses some properties of metals and some properties of nonmetals

Molecular Compound (Covalent Compound)

Composed of molecules formed by atoms of two or more different elements

Molecular Formula

Formula indicating the composition of a molecule of a compound and giving the actual number of atoms of each element in a molecule of the compound

Monatomic Ion

Ion composed of a single atom

Neutron

Uncharged, subatomic particle located in the nucleus

Nomenclature

System of rules for naming objects of interest

Nonmetal

Element that appears dull ,poor conductor of heat and electricity

Nucleus

Massive, positively charged center of an atom made up of protons and neutrons

Oxyacid

Compound that contains hydrogen, oxygen, and one other element, bonded in a way that imparts acidic properties to the compound (ability to release H+ ions when dissolved in water)

Oxyanion

Polyatomic anion composed of a central atom bonded to oxygen atoms

Period (Series)

Horizontal row of the periodic table