Honors Chem Sem 1 Final Test

Scientific Method

Scientific Method

a method of procedure that consists of a systematic observation, measurement, experiment, and the formulation and modification of the hypothesis

Hypothesis

superstition or proposed explanation made on the basis of limited evidence as a starting point for further investigation

Experiment

scientific procedure undertaken to make a discovery, test a hypothesis, or demonstrate a known fact

Theory

an interpretation or possible explanation of why nature behaves in a particular way; explanation of behavior

Law

explains why something happened based on the observations, hypotheses, and experiments done; measurable behavior

Observation

remark, statement or comment based on something one has seen, heard, or noticed

Theory Model

a description or representation used to understand the way in which a process works

Significant Figures

digits in a measurement that are known precisely plus a last digit that must be estimated

Leading zeros

zeros that precede all the nonzero digits; not significant; aka beginning zeros

Captive zeros

zeros that fall between nonzero digits; significant; aka middle zeros

Trailing zeros

zeros at the right end of a number; significant only if number is written with a decimal point; aka ending zero

Measurement

a value that represents a physical quantity

Scientific Notation

a way of expressing numbers as the product of a coefficient and a power of 10

Matter

anything that has mass and takes up space

Density

ratio of mass to volume; mass/volume; g/cm3 or g/mL

Substance

particular kind of matter that has a uniform and definite composition

Element

substance with one type of atom, simplest form of matter, not separated

Compound

substance that contains 2 or more elements chemically combined, can be separated, different atoms

Physical Properties

characteristic of a substance that can change without the substance becoming a different substance

Physical Change

change in appearance of a substance, but the atoms or molecules stay the same

Chemical Properties

characteristic that describes the ability of a substance to change into a different substance

Chemical Change

forming one or more substances, resulting substance would have a different chemical formula

Mixture

blend or two or more substances

Homogenous

mixture that is same throughout

Heterogenous

mixture containing regions with differing properties

Law of Conservation of Mass

in any physical or chemical reaction mass is neither created nor destroyed, it is conserved; same mass at beginning and end of reaction

Atom

fundamental unit of matter

Nucleus

dense center of an atom, contains protons and neutrons

Proton

positively charged subatomic particle found in the nucleus of an atom

Neutron

neutrally charged subatomic particle found in the nucleus of an atom

Electron

negatively charged subatomic particle found outside the nucleus of an atom

Atomic Number

the number of protons in an atom, defines the atom of an element

Mass Number

the sum of the number of protons and neutrons in an atom

Isotopes

atoms that have the same number of protons but a different number of neutrons

Ions

atoms that have gained or lost electrons and have a positive or negative charge

Alpha Particle

a particle consisting of two protons and two neutrons, with a double positive charge

Beta Particle

an electron resulting from the breaking apart of a neutron

Gamma Radiation

high energy photon (electromagnetic) emitted by a radioisotope

Half Life

time required for one half of the nuclei of a radioisotope sample to decay to products

Nuclear Fusion

nuclei combine to produce nucleus of greater mass

Fusion reactions

Reactions in which small nuclei combine, releasing more energy than fission reactions.

Fission reactions

Reactions in which large nuclei split, releasing less energy than fusion reactions.

Geiger counters

Devices used for detecting radiation.

Scintillation counters

Devices used for detecting radiation.

Film badges

Devices used for detecting radiation.

Uses for radioactive material

Diagnosing medical problems, carbon dating, smoke detectors, x-rays, medical treatment.

Bohr Model

A model of the atom that explains the energy levels of electrons.

Energy levels

Analogous to the rungs of a ladder, electrons can only exist at specific energy levels and cannot be located between them.

Quantum of energy

The amount of energy required to move an electron from one energy level to another.

Electron shells

Correspond to regions in space that electrons can occupy and can only hold a certain number of electrons.

Core electrons

Electrons located in all of the inner shells of an atom.

Valence electrons

Electrons occupying the outermost shell of an atom.

Quantum Mechanical Model

A mathematical solution that describes the energy levels and probability of finding an electron at a certain distance from the nucleus.

Principal Quantum Number

Represents the energy level or shell of an electron.

Energy subshell

Represents the type and shape of the orbital in which an electron can be found.

Electron configuration

Describes the arrangement of electrons in an atom, including the principal quantum number, energy subshell, and number of electrons in each subshell.

Aufbau Principle

Electrons enter orbitals of lowest energy first.

Pauli Exclusion Principle

An atomic orbital can describe at most two electrons, and they must have opposite spins.

Hund's Rule

When electrons occupy orbitals of equal energy, they don't pair up until they have to.

Atomic Spectra

When electrons are excited to higher energy levels and then fall back to the ground state, they emit light at specific wavelengths in the visible spectrum.

Bonding

The attraction between two atoms to achieve a more stable state.

Chemical Bonds

Ionic bonds involve the transfer of electrons between a metal and nonmetal, while covalent bonds involve the sharing of electrons between nonmetals.

Ionic Bonds

Formed by the electrostatic attraction between positive and negative ions, resulting from the transfer of electrons.

Covalent Bonds

Formed by the sharing of electrons between nonmetal atoms.

Metallic Bonds

Formed by a "sea of electrons" surrounding metal atoms.

Bond Energy

The energy required to break a bond.

Empirical Formula

The formula of a compound expressing the smallest whole number ratio of atoms.

Molecular Formula

The chemical formula of a molecular substance, showing the number and kind of each atom in a single molecule.

Alkanes

Saturated hydrocarbons with only single bonds.

Alkenes

Hydrocarbons that contain a double covalent bond.

Alkynes

Hydrocarbons that contain a triple covalent bond.

Aromatic hydrocarbons

Hydrocarbons with six-membered rings and delocalized electrons.

Functional Groups

Sets of atoms bonded together in a specific way that define the chemical and physical properties of organic compounds.

Polarity

Some covalent compounds share electrons equally (nonpolar), while others do not (polar).

Intermolecular Forces

Forces of attraction between molecules, including dipole-dipole forces, hydrogen bonds, and London dispersion forces.

Balancing Equations

The process of ensuring that the number of atoms of each element is the same on both sides of a chemical equation.