Praxis II - Middle School Science 5440 - Basic Principles of Science

Solid

Has a definite volume and does not need a container to maintain its shape. The structure can be either crystalline or amorphous.

Crystalline Solid

Has a regular and repeating arrangement of particles. There are four different types: ionic, molecular, network, and metallic.

Amorphous Solid

Has no regular or repeating arrangement of particles.

Heat of Fusion

The amount of energy needed to overcome the IMF that hold the substance together as a solid.

Vapor pressure

Exerted by gas molecules when in equilibrium with its liquid phase.

Viscosity

The resistance of liquid to flow.

Surface Tension

A measure of the resistance of a liquid to spread out.

Boyle's Law

For the fixed amount of an ideal gas at a given temperature, the pressure and volume of that gas are inversely related. When pressure increases, volume decreases.

Charles's Law

For a fixed amount of an ideal gas at a given temperature, the volume of the gas is directly proportional to its absolute (Kelvin) temperature.

Gay-Lussac's Law

For a fixed amount of an ideal gas at a given volume, the pressure of the gas is directly proportional to its absolute (Kelvin) temperature.

Big Bang

The theorized origin of the universe.

Nuclear Fusion

Occurs within the core of a star; forms successively larger atoms.

Supernovas

Explosion of massive stars; scientists theorize that elements heavier than iron, such as gold and lead, are formed during these events.

Transmutation

The process in which atomic nuclei are changed. Has allowed scientists to create synthetic or man-made elements.

Superheavy elements

Elements with an atomic number greater than 106. Created in a synchrotron or particle accelerator.

Physical change

A change that alters the physical state of a substance without changing its composition or forming a new product. No new substances are formed, and no chemical bonds are made or broken during this type of change.

Chemical change

A change in which a chemical reaction occurs.

Chemical Reaction

During this reaction, bonds are broken and formed, creating new products that have different chemical properties from the original raw materials or reactants.

Law of conservation of mass and energy

States that atoms and energy cannot be destroyed during a chemical reaction.

Energy

Capacity to do work. Cannot be created or destroyed, but it can be transferred and change form.

Potential Energy

Stored energy

Kinetic energy

Energy of motion or action

Temperature

Measure of heat energy in a system

Heat

Thermal energy that is moving from a hot to a colder temperature

Thermal energy

A type of energy stored in an object and is a measure of the random kinetic energy of each atom in that object

Specific heat

Thea mount of heat required to increase the temperature of a unit mass of a substance at 1 degree Celsius.

First law of thermodynamics

Energy is interchangeable, but energy cannot be created or destroyed.

Hess's Law

The Heat (energy) requirement for any reaction is constant and independent of the manner in which the reaction takes place.

Second law of thermodynamics

No natural reaction or process can occur unless it is accompanied by an increase in entropy.

Entropy

A measure of randomness of the universe. Tells how much energy is available to do work.

Democritus

Created the term "atom".

Atoms

Smallest part of an element that retains the properties of that element. Made of protons, neutrons, and electrons.

Antoine Lavoisier

Discovered that the mass of the products of a chemical reaction were exactly the same as the starting materials.

Law of conservation of mass

No matter is lost during a chemical reaction.

Dalton's laws

All matter is made of very small and nonbreakable particles called atoms; all atoms of an element are similar, and atoms of a different element are different; and atoms are not created or destroyed in a chemical reaction.

JJ Thomson

Demonstrated that electrons are part of the atom; they are very small and have a negative charge.

Ernest Rutherford

Determined that positive charges (protons) are contained in a nucleus. He also concluded that most of an atom is empty space, and the negatively charged electrons swarm around the positively charged nucleus.

Niels Bohr

Discovered electrons travel around the nucleus in well defined energy levels. Electrons that absorb energy move to a higher energy level. Electrons that give off light energy return to their normal ground state or energy level.

James Chadwick

Discovered the neutron.

Electromagnetic force (EMF)

Holds an electron in orbit around the nucleus; the opposite charges within the positively charged protons and negatively charged electrons

Electron Configuration

Describes the "electron address" for the atom; describes the location of each electron within that atom.

Principal quantum; principal energy levels or shells

Numbered 1-7, correspond to the period numbers on the periodic table

Subshells

Compose the principal energy levels; noted as s, p, d, and f, based on the maximum number of electrons they can hold.

Orbitals

Compose subshells and are the most specific location for electrons; each can hold a maximum of two electrons

Atomic size

Dependent on the number of electrons and their proton balance.

Ionization energy

Energy required to remove an electron from a neutral atom; increases moving across a period and decreases moving down a group

Chemical Reactivities

Features of atoms in the same group

Electronegativity (strength)

Strength of electron attraction to the nucleus; decreases moving down a group and increases moving across a period

Electrical charge

Usually the same as the group number for elements in groups 1-3; elements in group 18 have no charge; elements in groups 5-7 obey the following equation: group number - 8 = ionic charge

Radioisotope

Unstable radioactive isotope; spontaneously emits energy in order to form a more stable nucleus

Isotopes

Atoms of the same element that have a different number of neutrons

Radioactive decay

The process in which an unstable radioactive nucleus or radioisotope emits radiation, thereby forming a more stable nucleus with a different composition

Half-life

The time it takes for one-half of the radioactive isotope to decay

Radioactivity

The energy or nuclear radiation emitted from a radioactive isotope

Radiation

Process of emitting radiant energy; particles and nuclear energy are released by radioactive isotopes; four types of radiation released: alpha, beta, gamma radiation, and positron

Alpha Decay

The nucleus ejects two protons and two neutrons.

Alpha particles

High-energy particles that decrease the number of protons and neutrons in the nucleus by two each

Beta Decay

Occurs when a neutron splits into a proton and an electron, with the proton remaining in the nucleus

Beta particle

High energy electron

Gamma decay

Releases gamma rays, or high-energy radiation from a radioactive nucleus. Not a true decay reaction because the nucleus emits a high-energy photon, but the number of protons and neutrons remain the same.

Positron

Antiparticle of a beta particle; the charge on a positron is positive. Formed when a proton reforms into a neutron.