Term | Definition |
chemistry | Study of the composition and properties of substances, and the changes those substances can undergo |
scientific method | Orderly and systematic approach to gathering info in order to answer questions about the world |
observation | Fact that is noticed either quantitatively or qualitatively |
hypothesis | Proposition and unproved explanation of observed facts (educated guess) |
experiment | Carefully devised procedure for making observations and gathering data |
conclusion | Judgement or opinion formed as a result of analyzing data |
natural law | Description of a phenomenon that has been repeatedly and uniformly observed in nature |
theory | Logical and time tested explanation of a phenomenon that occurs in the natural world |
variable | Factor being tested In an experiment |
experimental control | Factor that remains constant during an experiment |
metric system | Decimal system of measurement used internationally |
international system of units (SI) | System of units that is an extension of the metric system; includes 7 base units |
base unit | One of seven units used in the SI system |
mass | Quantify of matter in a unit |
derived unit | Unit in the SI system that results in a combination of base units |
volume | Amount of space that an object occupies |
metric prefix | Syllable or group of syllables attached to the beginning of a metric unit in order to make the unit larger or smaller |
precision | Measure of the agreement between the numerical values of two or more measurements that have been using the same method; when the same values result from repeated measurements, the measurements are said to have high ______ |
accepted value | Standard value for a measurement |
accuracy | Indicates how close a measurement is to it's accepted value |
significant digit | Digit in the measurement that is certain, plus one digit that is estimated |
percent error | Relative error as determined by finding the difference between an accepted value an d a measured value, dividing the result by the accepted value and multiplying the quotient by 100 |
density | Mass of an object divided by its volume |
dimensional analysis | Technique for converting between units by using the numerical relationships between the units by using the numerical relationships between the units |
unit equality | Equation that shows the numerical relationships between 2 units |
conversion factor | Fraction having a value of one that is written from a unit equality and is used to change a measurement from one unit to another |
energy | Capacity to do work or transfer heat |
kinetic energy | Energy of motion |
potential energy | Stored energy or energy of position |
joule | Basic unit of energy |
law of conservation of energy | Natural law describing the fact that energy is neither created nor destroyed in any process |
kelvin scale | S.I temperature scale with a zero point of absolute zero |
absolute zero | Theoretically lowest temperature that can be reached
-273.15 C or 0 K |
matter | Anything that has mass and volume |
solid | State at which matter holds a definite shape and volume |
liquid | State in which matter does not hold a definite shape but does occupy a definite volume |
gas | State in which matter doesn't have a definite shale or volume |
physical property | Characteristic of a substance that can be observed without altering the identity of the substance |
chemical property | Characteristic of a substance that can't be observed without altering the identity of the substance |
physical change | Process by which a substance undergoes a change that does not alter its identity |
chemical change | Process by which the composition and properties of a substance change, thus altering the identity of the substance. Products a new substance |
Avogadro's number | 6.02 x 10*23 |
element | Substance that can't be separated into a similar substance by a chemical change |
compound | Substance that contains two or more elements chemically combined |
pure substance | Substance made of one kind of material with a unique set of chemical and physical properties |
mixture | Blend of two or more pure substances that are not chemically combined |
heterogeneous mixture | Mixture in which the particles are not uniformly intermingled and that therefore has visibly different parts |
homogeneous mixture | Mixture in which the particles are uniformly intermingled and that therefore doesn't have visibly different parts |
atom | Smallest particle of an element that retains the chemical identity of that element |
law of constant composition | Natural law describing the fact that a given compound always contains the same elements in the same properties |
atomic theory of matter | Proposed by john dalton. States that atoms are neither created nor destroyed in a chemical reaction, all atoms of the same element are identical but not to other atoms |
cathode ray | Stream of electrons emitted by a negatively charged electrode and attracted by a positively charged electrode |
cathode ray tube | Evacuated glass tube in which a stream of electrons emitted by a cathode strikes a fluorescent material causing it to glow |
electron | Negatively charged particle in an atom |
radioactivity | Spontaneous emission of radiation from an atom |
nucleus | Concentrated core of an atom, which contains protons and neutrons |
proton | Positively charged particle in the nucleus of an atom |
neutron | Neutral particle in the core of an atom |
atomic number | Number of protons in the nucleus |
atomic mass unit | Unit by which the mass of an atom or the atomic particle is expressed. |
ion | Atom or group of atoms that has a positively or negative charge because it has lost or gained electrons |
isotope | Atom that has the same number of protons as another atom but has a different number of neutrons |
mass number | Sum of the number of protons and neutrons in the nucleus of an atom |
atomic mass | Weighted average of the masses of the existing isotopes of an element |
nuclear reaction | Process that changes the composition of the nucleus of an atom |
strong nuclear force | Attractive force between the particles in the nucleus. In a stable atom, it overcomes the force of repulsion |
radioactive decay | Spontaneous breakdown of an unstable atomic nucleus |
nuclear equation | Equation that describes the changes that occur during radioactive decay |
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