Term | Definition |
matter | the material of the universe - has mass and takes up space |
substance | a sample of matter having a constant (uniform or definite) composition |
atoms | fundamental unit of which elements are made, smallest particle of an element that retains the properties of that element |
elements | substances made by bonding two or more of the same atoms together |
compounds | substances made by bonding two or more different atoms in specific ways |
molecules | a collection of atoms bonded together that behave as a unit |
allotropes | different physical forms of the same element |
states of matter | solid, liquid, and gas |
solid | matter that has definite shape and volume |
liquid | matter that has definite volume, but takes the shape of its container |
gas | matter that takes both the shape and volume of its container |
properties of matter | properties are physical or chemical characteristics of substances |
physical property | |
chemical property | a characteristic of a substance that describes the ability of that substance to change into a different substance |
physical changes | changes in a substance that do not change the chemical composition of the substance |
chemical changes | changes in a substance that change the chemical composition of the substance |
mixture | two or more substances (elements or compounds) that are physically combined |
homogeneous | a type of mixture that is completely uniform in composition |
heterogeneous | a type of mixture that is not uniform in composition |
distillation | used to separate two or more liquids taking advantage of differences in boiling points |
filtration | used to separate solids from liquids, or solids from other solids |
chromatography | used to separate substances with different masses that dissolve in a common solvent |
electrolysis | used to break compounds apart into elements, or to seperate ion susing electrical charge |
trace minerals | mineral that is essential but present in small quantities |
Law of Constant Composition | a given compound always contains the same proportions |
chemical formula | the types of atoms and the number of each type in each unit (molecule) of s given compound |
nucleus | central, dense core of the atom that contains most of the mass of the atom (protons + neutrons) |
proton | positively charged particle found in the nucleus of the atom |
neutron | neutral particle found in nucleus of the atom |
nucleon | particle in the nucleus - refers to either protons or neutrons |
electron | negatively charged particle found in the region surrounding the nucleus |
atomic number | the number of protons in the nucleus |
mass number | the sum of the number of neutrons and protons in a given nucleus |
isotopes | atoms with the same number of protons but different number of neutrons |
isotope abundance | percentage of that isotope that occurs naturally in an element |
isotope mass | mass of an atom of that isotope |
atomic mass | mass of an atom measured in "atomic mass units" (amu) |
average atomic mass | weighted average mass of atoms in a naturally occurring sample of the element |
Dalton | atom - original atomic theory |
William Crookes | cathode ray tube - invisible tays flow from cathode to anode |
J.J. Thomson | electron - cathode ray - plum pudding model - tiny negative particles can be emitted |
Robert Millikan | oil drop experiment - charge to mass ratio |
Rutherford | nucleus, proton - gold foil experiment - dense center of positive charge; center composed of positive particles |
Bohr | Bohr model - energy levels |
Schrodinger | quantum-mechanical model - location of electron has a probability associated with it |
Chadwick | neutron - center also has neutral particles |