GenChem1

What is matter?

Anything that has mass and occupies space.

Differentiate between mass and weight.

Mass is the amount of matter in an object; weight is the force of gravity acting on that mass.

What are the three states of matter?

Solid, liquid, and gas.

What is a physical property?

A characteristic that can be observed without changing the substance's composition.

What is a chemical property?

A characteristic that can only be observed when a substance undergoes a chemical change.

Define density.

Density is mass per unit volume (D = m/V).

What is the SI unit of temperature?

Kelvin (K).

Convert 25°C to Kelvin.

25°C + 273.15 = 298.15 K.

What is accuracy in measurement?

How close a measured value is to the true value.

What is precision in measurement?

How close repeated measurements are to each other.

Who discovered the electron?

J.J. Thomson through the cathode ray experiment.

What did Rutherford's gold foil experiment show?

That atoms have a small, dense, positively charged nucleus.

What is the atomic number (Z)?

The number of protons in an atom.

What is the mass number (A)?

The total number of protons and neutrons in an atom.

What are isotopes?

Atoms of the same element with different numbers of neutrons.

What does the Bohr model describe?

Electrons orbit the nucleus in fixed energy levels.

What is the quantum mechanical model of the atom?

It describes electrons as wave-like entities in orbitals, not fixed paths.

Define an orbital.

A region in space where there is a high probability of finding an electron.

What are the four quantum numbers?

Principal (n), angular momentum (l), magnetic (ml), and spin (ms).

What is the Pauli exclusion principle?

No two electrons in an atom can have the same set of four quantum numbers.

What is Hund's rule?

Electrons fill degenerate orbitals singly before pairing.

What is the Aufbau principle?

Electrons occupy the lowest-energy orbital available first.

What is periodicity?

The repeating pattern of chemical and physical properties in the periodic table.

What is atomic radius?

Half the distance between nuclei of identical atoms bonded together.

How does atomic radius change across a period?

It decreases across a period due to increasing nuclear charge.

How does atomic radius change down a group?

It increases down a group due to added energy levels.

What is ionization energy?

The energy required to remove an electron from a gaseous atom.

What is electronegativity?

The tendency of an atom to attract electrons in a bond.

Which element has the highest electronegativity?

Fluorine.

What is electron affinity?

The energy change when an electron is added to a neutral atom.

What is an ionic bond?

The electrostatic attraction between oppositely charged ions.

What is a covalent bond?

A bond formed by the sharing of electrons between atoms.

What is a metallic bond?

Attraction between metal cations and delocalized electrons.

What is a polar covalent bond?

A covalent bond with unequal sharing of electrons.

What causes polarity in molecules?

Differences in electronegativity between bonded atoms.

What is resonance?

When more than one Lewis structure can represent a molecule.

What is the VSEPR theory used for?

To predict molecular shapes based on electron pair repulsion.

What is hybridization?

Mixing of atomic orbitals to form new hybrid orbitals for bonding.

What is a sigma bond?

A bond formed by head-on overlap of orbitals.

What is a pi bond?

A bond formed by side-to-side overlap of p orbitals.

What is molecular geometry of CH4?

Tetrahedral.

What is a mole?

The amount of substance that contains Avogadro's number (6.022Ã*10^23) of particles.

What is molar mass?

Mass of one mole of a substance, in g/mol.

How is percent composition calculated?

Mass of element / total molar mass Ã* 100%.

What is a limiting reactant?

The reactant that is completely consumed and limits the amount of product formed.

What is theoretical yield?

The maximum product amount predicted by stoichiometry.

What is actual yield?

The amount of product actually obtained from an experiment.

What is percent yield?

(Actual yield / Theoretical yield) Ã* 100%.

What is the law of conservation of mass?

Mass is neither created nor destroyed in a chemical reaction.

What is a chemical equation?

A representation of a chemical reaction using symbols and formulas.

What are the types of chemical reactions?

Combination, decomposition, single replacement, double replacement, and combustion.

What does a balanced equation show?

The stoichiometric relationship between reactants and products.

What is a redox reaction?

A reaction involving transfer of electrons between species.

What is oxidation?

Loss of electrons.

What is reduction?

Gain of electrons.

What is Boyle's Law?

At constant temperature, pressure is inversely proportional to volume (P ? 1/V).

What is Charles's Law?

At constant pressure, volume is directly proportional to temperature (V ? T).

What is Avogadro's Law?

At constant temperature and pressure, volume is directly proportional to moles of gas (V ? n).

What is the ideal gas law?

PV = nRT.

What is STP?

Standard Temperature (273.15 K) and Pressure (1 atm).

What is Dalton's Law of Partial Pressures?

Total pressure equals the sum of partial pressures of all gases in a mixture.

What is diffusion?

Movement of gas molecules from high to low concentration.

What is effusion?

Escape of gas molecules through a tiny hole without collisions.

What is thermochemistry?

The study of heat changes in chemical reactions.

What is the first law of thermodynamics?

Energy cannot be created or destroyed, only transformed.

Define system and surroundings.

System: part under study; surroundings: everything else.

What is enthalpy (?H)?

Heat change at constant pressure.

What is an exothermic reaction?

A reaction that releases heat (?H < 0).

What is an endothermic reaction?

A reaction that absorbs heat (?H > 0).

State Hess's Law.

The total enthalpy change is the same regardless of reaction pathway.

What is calorimetry?

Measurement of heat flow during physical or chemical processes.

What is specific heat capacity?

Amount of heat needed to raise the temperature of 1 g of a substance by 1°C.

What is the equation for heat transfer?

q = m Ã* c Ã* ?T.