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Chemistry 100 Exam 1


O.H.E.E. Observe, Hypothesize (question), Evaluate (test), Explain (theory)
Chemistry The science that seeks to understand the behavior of matter by studying what atoms and molecules do.
Scientific Method How scientists learn about the natural world; involves observations, laws, hypotheses, theories and experimentation.
Observation What you perceive; should be simply worded.
Hypotheses an idea or "hunch" supported by limited evidence; explains how something works, but not why; specific and testable.
Theory theories attempt to explain why something works; they're supported by evidence from many tested hypotheses, but not testable as a yes/no question.
Law Refers to something that happens very consistently within specific limits
Mass the measure of the quantity of matter within an object/subject
Energy the capacity to do work energy is neither created or destroyed, rather it is expended or absorbed.
Significant Figures the non-place-holding digits in a measurement representing the precision of the measurement.
Precision In science, precision refers to the consistency of a measurement or finding, or how reproducible it is.
Accuracy In science, accuracy refers to how close you are to the target.
Significant figures - rule for multiplication and division round the answer to the number of significant figures in a calculated number with the least s.f.
Significant figures - rule for addition and subtraction round the answer to the value with the least number of s.f. after the decimal place.
Density Density=Mass/Volume commonly expressed in g/cm^3, g/mL, or g/L.
Matter anything that occupies space and has mass
Atom the smallest fundamental unit of matter
Molecule specific combinations of atoms (ex: H2O)
Law of the Conservation of Mass Mass is not created or destroyed in a chemical reaction
Law of the Conservation of Energy energy is neither created not destroyed
The 3 states of matter Solid, liquid and gas
Properties of a Solid Definite shape and volume; cannot be compressed; oscillates about a fixed point; atoms/molecules closely spaced
Properties of a Liquid Indefinite shape, but definite volume; compressible (takes shape of container); Atoms/molecules are closely spaced by free to move around.
Properties of a Gas Indefinite shape and volume; compressible; atoms/molecules spaced far apart and free to move around
Mixture composed of 2 or more different types of atoms or molecules in varying proportions
Pure Substance composed of one type of atom or molecule in fixed, definite proportions
Compound substance with 2 or more elements in fixed, definite proportions
Element a substance that cannot be broken down into simpler substances
Homogeneous Mixture composition is same throughout
Heterogeneous Mixture Composition varies from one region to another
Metal elements that usually lose electrons in chemical reactions
Non-Metal Elements that usually gain electrons in chemical reactions
Physical Change matter changes appearance, not composition (ex: water freezing)
Chemical Change matter changes composition and appearance (ex: burning gasoline or the melting of engine components together)
Chemical Property a property displayed only through change in composition
Physical Property a property displayed without changing composition
Exothermic Reaction a process that releases energy (ex: a dynamite explosion)
Endothermic Reaction a process that absorbs energy (ex: a cold pack)
Kelvin a temperature scale that avoids negative numbers by assigning "zero Kelvin" to the coldest temperature possible, absolute zero (-273.15 Celsius or -459.7 Fahrenheit)
Specific Heat Capacity the quantity of heat required to change 1 gram of a substance by 1 degree Celsius.
Potential energy energy associated with its position or composition Ex: water behind a damn - gravity is pushing until it is released
Kinetic energy the energy associated with its motion Ex: a rolling ball
alkali metals Group 1A of periodic table; highly reactive. Hydrogen, lithium, sodium, potassium, rubidium,cesium, francium
Alkaline earth metals Group 2A of periodic table; fairly reactive. Beryllium, magnesium, calcium, strontium, barium, radium
anion a negatively charged ion
atomic mass a weighted average of the masses of each naturally occurring isotope of an element; the average mass of the atoms of an element
atomic mass unit expresses atomic mass (amu)
atomic number The number of protons in the nucleus of an atom
cation a positively charged ion
charge a fundamental property of protons and electrons. charged particles experience forces such that like charges repel and unlike charge attract.
chemical symbol one or two letter abbreviation for an element
electron a negatively charged particle that occupies most of the atom's volume by contributes nearly nothing to its mass.
family or group (of elements) elements with similar properties organized into columns on the periodic table
halogens Group 7A elements on the periodic table; very reactive nonmetals. Fluorine chlorine,bromine,iodine,astatine, tennessine
ion an atom (or group) that has gained or lost one or more electrons so that it has an electric charge.
isotope One of two or more atoms with the same number of protons but different numbers of neutrons.
main-group elements Groups 1A-8A; the elements have properties that tend to be predictable based on their place in the periodic table.
mass number (A) the sum of the number of neutrons and protons in an atom.
metalloids Those elements that fall along the boundary between metals and nonmetals on the periodic table; properties intermediate of metals and nonmetals.
metals elements that tend to lose electrons in a chemical reaction; left side of periodic table;
neutron a nuclear particle with no electrical charge and nearly the same mass of a proton.
noble gasses Group 8A of the periodic table; chemically inert gasses (nonreactive). Helium, neon, argon, krypton, xenon, radon, organisson.
nonmetals elements that tend to gain electrons in a chemical reaction; upper right side of periodic table.
nuclear radiation the energy particles emitted from the nucleus of an atom when it is undergoing a nuclear process.
nuclear theory of the atom A theory stating that most of an atom's mass and all of its positive charge are contained in a small, dense nucleus. Most of the volume of the atom is empty space occupied by negatively charged electrons.
nucleus (of an atom) The small core containing most of the atom's mass and all of its positive charge. Made up of protons and neutrons.
percent natural abundance The percentage amount of each isotope of an element in a naturally occurring sample of the element.
periodic law A law that states that when the elements are arranged in order of increasing relative mass, certain sets of propertied reoccur periodically.
periodic table An arrangement of the elements in which atomic number increases from left to right and elements with similar properties fall in columns called families or groups.
proton A positively charged nuclear particle.
radioactive Describes a substance that emits tiny, invisible, energetic particles from the nuclei of its component atoms
semiconductor A compound or element exhibiting intermediate electrical conductivity that can be charged and controlled.
Created by: msmolloy01



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