Chem Units 1-2 Terminology

scientific method

approach to acquire knowledge through the observation of phenomena

experiment

an observation of natural phenomena tested in a controlled and repeatable process from which a rational conclusion can be made

hypothesis

a tentative and testable explanation for an observation or a series of observations

theory

a tested explanation of basic natural phenomena 

law

a statement that summarizes a vast number of experimental observations, and describes or predicts some aspect of the natural world

two components of a measurement

number and unit

precision

agreement among repeated measurements

accuracy

agreement between a measured value and the accepted or true value

SI unit for length

meter (m)

SI unit for mass

kilogram (kg)

SI unit for time

seconds (s)

SI unit for temperature

kelvin (K)

SI unit for amount of substance

mole (mol)

SI unit for electric current

ampere (A)

SI unit for pressure

pascal (Pa)

SI unit for heat

joule (J)

dimensional analysis

method for calculation where you carry along the units for the quantities to convert units from what you start with to what you need in the end

chemistry

the study of composition and structure matter and of the changes that matter undergoes

matter

whatever occupies space and can be perceived by our senses

law of conservation of mass

no mass is lost from the start of a process to the end

extensive property

depends on the amount of substance

intensive property

does not depend on the amount of substance

physical property

can be observed without doing a chemical reaction 

chemical property

can only be observed through a chemical reaction

pure substance

a type of matter with the same physical and chemical properties throughout, cannot be separated into simpler substances through a physical process

mixture

matter that is a combination of two or more pure substances and can be separated by physical processes

elements

a type of pure substance that cannot be separated into simpler substance by any chemical processes

common diatomics

Br2, I2, N2, Cl2, H2, O2, F2

common polyatomic molecules

P4, S8

compounds

pure substances composed of two or more different elements bonded together in fixed proportions that can be broken down by chemical means

law of constant composition/law of definite proportions

all samples of a particular compound contain the same elements in the same proportions

homogenous mixture

components are distributed uniformly through the sample and have no visible boundaries or regions

heterogenous mixture

components are not distributed uniformly and there may be distinct regions with different compositions

three ways to separate mixtures

distillation, filtration, and chromatography

atomic mass units

unit used to express the relative masses of atoms and subatomic particles

mass of proton and neutron

about 1 amu

mass of electron

about 0 amu

name of first group in periodic table

alkali metals

name of second group in periodic table

alkaline earth metals

name of groups 3-12 in periodic table

transition metals

name of group 17 in periodic table

halogens

name of group 18 in periodic table

noble gasses

properties of metals

shiny solids, conduct heat and electricity, are malleable

properties of non-metals

solids, liquids, and gases, nonconductors, solids are brittle

properties of metalloids

shiny solids (like metals), brittle (like nonmetals), semi conductors

components of nuclide symbol

atomic mass (protons + neutrons), atomic symbol, atomic number (protons only)

isotopes

atoms of the same element that contain different numbers of neutrons and thus have different atomic mass (but not different identities)

average atomic mass

weighted average mass of all isotopes of an element

natural abundance

proportion of a particular isotope generally represented by a percentage

ions

neutral atoms that gain/lose electrons to become ions - they are held together by electrostatic force

cations

ions with positive charge

anions

ions with negative charge

ionic compounds

formed by a metal cation and a nonmetal anion

molecular compounds

formed by atoms held together with covalent bonds (two nonmetals)

molecular formula

shows number and type of atoms present in one molecule of a compound

empirical formula

shows the smallest whole-number ratio of elements in a compound

polyatomic ions

charged group of two or more atoms joined together by covalent bonds

oxoanions

polyatomic anions containing oxygen in combination with one or more other elements