Chemistry: Matter, Atoms, and Stoichiometry

Flashcards covering matter properties, measurement units, stoichiometry, atomic theory, and chemical nomenclature based on university chemistry lecture notes.

Chemistry

The scientific study of matter and its properties, the changes that matter undergoes, and the energy associated with those changes.

Matter

Anything that has mass and volume.

Substance

A type of matter that has a defined, fixed composition.

Solid

A state of matter that has a fixed shape which does not conform to the container shape and is not necessarily defined by rigidity or hardness.

Liquid

A state of matter that has a varying shape conforming to the container, but only to the extent of its volume, characterized by having an upper surface.

Gas

A state of matter that has a varying shape that conforms to and fills the entire container, lacking a surface.

Physical properties

Characteristics shown by a substance itself, without changing into or interacting with another substance, such as color, melting point, electrical conductivity, and density.

Physical change

Occurs when a substance alters its physical properties but not its composition, such as changes of state.

Chemical properties

Characteristics shown by a substance as it changes into or interacts with another substance, including flammability, corrosiveness, and reactivity with acid.

Chemical change

Also known as a chemical reaction, it occurs when one or more substances are converted into one or more substances with different composition and properties.

Malleable

A physical property describing a substance, like copper, that can be easily hammered into sheets.

Ductile

A physical property describing a substance, like copper, that can be drawn into wires.

Energy

The ability to do work.

Potential energy

The energy due to the position of the object relative to other objects.

Kinetic energy

The energy due to the motion of the object.

SI unit system

A universally accepted system based on seven fundamental (or base) units, with all other units being derived.

Angstrom ($\text{Å}$)

An older unit of length still in use, where $1\,\text{Å} = 10^{-10}\,m = 0.1\,nm$.

Meter ($m$)

The SI base unit for length, currently defined as the distance travelled by light in a vacuum in $1/299,792,458$ of a second.

Second ($s$)

The SI unit of time defined as $9,192,631,770$ oscillations of microwave radiation absorbed by gaseous cesium atoms cooled to around $10^{-6}\,K$.

Dimensional analysis

The use of conversion factors in calculations to convert from one unit to another.

Density

The ratio between the mass and volume of a substance.

Extensive properties

Properties that are dependent on the amount of substance present, such as mass and volume.

Intensive properties

Properties that are independent of the amount of substance present, such as density.

Leading zeros

Zeros that precede all nonzero digits; they do not count as significant figures.

Captive zeros

Zeros between nonzero digits; these always count as significant figures.

Trailing zeros

Zeros at the right end of a number; they are significant only if the number contains a decimal point.

Exact numbers

Numbers determined by counting, from conversion factors, or from formulas, which are assumed to have an infinite number of significant figures.

Mole

The SI unit for amount of substance, defined as the amount that contains the same number of entities as the number of atoms in $12\,g$ of carbon-12.

Avogadro’s number

The number equivalent to one mole, which is $6.022 \times 10^{23}$ entities.

Molar mass ($M$)

The mass of a mole of a substance's entities (atoms, molecules, or formula units) expressed in grams per mole ($g/mol$).

Mass percent

Also called weight percent, it expresses how much of an element is present in a given amount of compound.

Empirical formula

A chemical formula that shows the lowest whole number of moles and the relative number of atoms of each element in a compound.

Molecular formula

A chemical formula that shows the actual number of atoms of each element in a molecule.

Combustion analysis

A method used to measure the amounts of carbon and hydrogen in a combustible organic compound by burning it in an excess of pure $O_2$.

Chemical equation

A statement that uses formulas to express the identities and quantities of substances involved in a chemical or physical change.

Stoichiometric coefficient

A balancing coefficient used to match the numbers of each type of atom on both sides of a chemical equation.

Ionic compounds

Compounds composed of ions, which are charged particles formed when an atom gains or loses electrons.

Covalent substances

Substances that form when atoms of elements (usually nonmetals) share electrons.

Binary ionic compound

The simplest type of ionic compound, typically formed when a metal reacts with a nonmetal.

Cation

A positively charged ion formed when a metal atom loses one or more electrons.

Anion

A negatively charged ion formed when a nonmetal atom gains one or more electrons.

Coulomb's Law

A law stating that ions with higher charges or smaller sizes attract or repel each other more strongly because the charges are closer or more intense.

Polyatomic ions

Ions consisting of two or more atoms bonded covalently that carry a net positive or negative charge.

Oxyanions

Polyatomic ions where an element is bonded to one or more oxygen atoms, often named with suffixes like -ate or -ite.

Hydrates

Ionic compounds containing a specific number of water molecules, which are indicated after a centered dot in the formula.

Mixture

Consists of two or more substances that are physically intermingled rather than chemically combined, and can be separated by physical changes.

Heterogeneous mixture

A mixture with one or more visible boundaries among its components, meaning its composition is not uniform.

Homogenous mixture (solution)

A mixture with no visible boundaries because components are individual atoms, ions, or molecules, resulting in a uniform composition.

Filtration

A basic separation technique based on differences in particle size, used to separate solids from liquids.

Crystallization

A separation technique based on differences in solubility.

Distillation

A separation technique that separates components based on differences in volatility.

Chromatography

A separation technique based on differences in solubility as a mobile phase flows through a stationary phase.

Element

The simplest type of matter with unique physical and chemical properties, consisting of only one kind of atom.

Compound

A substance consisting of two or more different elements that are bonded chemically in fixed parts by mass.

Law of Mass Conservation

Credited to Antoine Lavoisier, it states that the total mass of substances does not change during a chemical reaction.

Law of Definite Composition

Also called the law of constant composition, it states that a compound is composed of the same elements in the same parts by mass regardless of its source.

Law of Multiple Proportions

States that if elements A and B react to form two compounds, the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers.

Dalton’s Atomic Theory

Presented in 1808 by John Dalton, it postulates that all matter consists of atoms, atoms cannot be converted into other elements, and compounds result from specific ratios of atoms.

Cathode ray tube experiment

The experiment used by J.J. Thomson in 1897 to discover the mass/charge ratio of electrons.

Oil-drop experiment

The experiment conducted by Robert Millikan in 1909 to measure the charge of an electron as $1.602 \times 10^{-19}\,C$.

Nucleus

A tiny, central region of the atom containing all positive charge and essentially all mass, discovered by Ernest Rutherford.

Proton ($p^+$)

Positively charged subatomic particles located in the nucleus.

Neutron ($n^0$)

Subatomic particles with no charge, discovered by James Chadwick in 1932.

Atomic number ($Z$)

The number of protons in the nucleus of each of an element's atoms.

Mass number ($A$)

The total number of protons and neutrons in the nucleus of an atom.

Isotopes

Atoms of an element that have the same atomic number but different numbers of neutrons and mass numbers.

Dalton ($Da$)

Current name for the atomic mass unit ($amu$), defined as $1/12$ of the mass of a carbon-12 atom, equivalent to $1.66054 \times 10^{-24}\,g$.

Metals

Elements generally located on the left and center of the periodic table that are malleable, ductile, lustrous, and conduct electricity.

Nonmetals

Elements that tend to gain electrons to form anions.

Metalloids

Also called semi-metals, these elements share properties of both metals and nonmetals and act as good semiconductors.

Chemistry

The scientific study of matter and its properties, the changes that matter undergoes, and the energy associated with those changes.

Matter

Anything that has mass and volume.

Substance

A type of matter that has a defined, fixed composition.

Solid

A state of matter that has a fixed shape that does not conform to the container shape and is not necessarily defined by rigidity or hardness.

Liquid

A state of matter that has a varying shape that conforms to the container shape, but only to the extent of the volume, possessing an upper surface.

Gas

A state of matter that has a varying shape that conforms to the container shape and fills the entire container, thus lacking a surface.

Physical properties

Characteristics shown by a substance itself without changing into or interacting with another substance, such as color, melting point, electrical conductivity, and density.

Physical change

Occurs when a substance alters its physical properties but not its composition, such as changes in the state of matter.

Chemical properties

Characteristics shown by a substance as it changes into or interacts with another substance, such as flammability, corrosiveness, and reactivity with acid.

Chemical change

Also known as a chemical reaction, it occurs when one or more substances are converted into substances with different compositions and properties.

Energy

The ability to do work.

Potential energy

The energy due to the position of the object relative to other objects.

Kinetic energy

The energy due to the motion of the object.

SI unit system

A universally accepted system based on seven fundamental (base) units, with all other units being derived combinations of these seven.

Angstrom ($Å$)

An older unit of length still in use, where $1 \text{ Å} = 10^{-10} \text{ m} = 0.1 \text{ nm}$.

Second ($s$)

The SI unit of time defined as the duration of $9,192,631,770$ oscillations of microwave radiation absorbed by gaseous cesium atoms cooled to around $10^{-6} \text{ K}$.

Dimensional analysis

The use of conversion factors (ratios used to express a quantity in different units) in calculations.

Density

The ratio between the mass and volume of a substance ($\text{Density} = \frac{\text{mass}}{\text{volume}}$).

Extensive properties

Properties that are dependent on the amount of substance present, such as mass and volume.

Intensive properties

Properties that are independent of the amount of substance present, such as density.

Mole

The SI unit for amount of substance, defined as the amount containing the same number of entities as the number of atoms in $12 \text{ g}$ of carbon-12.

Avogadro’s number

The number of entities in one mole, equivalent to $6.022 \times 10^{23} \text{ entities } \text{mol}^{-1}$.

Molar mass ($M$)

The mass of a mole of a substance's entities (atoms, molecules, or formula units) expressed in units of $g \text{ mol}^{-1}$.

Mass percent

Also called weight percent, it is the percentage by mass of an element within a given amount of a compound.

Empirical formula

A formula that shows the lowest whole number of moles and the relative number of atoms of each element in a compound.

Molecular formula

A formula that shows the actual number of atoms of each element in a single molecule of a substance.

Combustion analysis

A method used to measure the amounts of carbon and hydrogen in a combustible organic compound by burning it in excess pure $O_2$ and measuring the resulting $CO_2$ and $H_2O$.

Chemical equation

A statement using formulas to express the identities and quantities of substances involved in a chemical or physical change.

Ionic compounds

Compounds composed of ions (charged particles) that form when atoms transfer electrons from one element (typically a metal) to another (typically a nonmetal).

Covalent substances

Substances that form when atoms of elements (usually nonmetals) share electrons to form chemical bonds.