Chemistry Chapter 1 Vocabulary Words

Front 1

experiments

Back 1

systematic observations or measurements, preferably made under controlled conditions

Front 2

hypotheses

Back 2

tentative explanations for scientific observations

Front 3

laws

Back 3

verbal or mathematical descriptions of a phenomenon that allows for general predictions. A law says what happens, not why it happens

Front 4

theories

Back 4

statements that attempt to explain why nature behaves the way it does. They tend to be incomplete and imperfect, evoloving with time to explain new facts as they are discovered

Front 5

scientific method

Back 5

the procedure scientists use to search for answers to questions and solutions to problems

Front 6

mass

Back 6

the quantity of matter an object contains: mass is a fundamental property of an object that does not depend on its location

Front 7

gas

Back 7

one of the three disinct states of matter under normal conditions, gases have neither fixed shapes nor fixed volumes and expand to fill their containers completely

Front 8

liquid

Back 8

liquids have a fixed volume but flow to assume the shape of their containers

Front 9

solid

Back 9

solids are relatively rigid and have fixed states and volumes

Front 10

mixtures

Back 10

a combination of two or more pure sustances in variable proportions in which the individual substances retain their identities

Front 11

homogenous mixture

Back 11

a mixture in which all portions of the material are in the same state, have no visible boundaries and are uniform throughout (koolaid)

Front 12

heterogeneous mixture

Back 12

a mixture in which a marterial is not completely uniform (chocolate chip cookies)

Front 13

elements

Back 13

a pure substance that cannot be broken down into simpler ones by chemical changes

Front 14

physical properties

Back 14

a characteristic that scientists can measure without changing the composition of the sample under study (mass, color, volume)

Front 15

chemical properties

Back 15

the characteristic ability of a substance to react to form new substances

Front 16

intensive property

Back 16

a physical property that does not depend on the amount of the substance (color, boiling point, melting point)

Front 17

extensive property

Back 17

a physical property that varies with the amount of the sustance (mass, weight, volume)

Front 18

density

Back 18

mass/volume an intensive property of matter, mass per unit volume

Front 19

atoms

Back 19

the fundamental, indivisible particles of which matter is composed

Front 20

electrons

Back 20

a subatomic particle with a negative charge

Front 21

nucleus

Back 21

the central core of an atom, where protons and any neutrons reside, comprises most of the mass of an atom but very little volume

Front 22

protons

Back 22

positive charge, opposite of the electron

Front 23

radioactivity

Back 23

the spontaneous emission of energy rays by matter

Front 24

atomic number

Back 24

(z) the number of protons in the nucleus of an atom of an element, the atomic number is different for each element

Front 25

isotopes

Back 25

atoms that have the same number of protons and hence the same atomic number (Z) but different numbers of neutrons

Front 26

mass number

Back 26

(A) the number of protons and neutrons in the nucleus of an atom of an element. Isotopes in an element only differ in their atomic mass

Front 27

atomic mass unit

Back 27

(amu) 1/12 of the mass of one atom of 12C

Front 28

ion

Back 28

a charged particle produced when one or more electrons is removed from or added to an atom or molecule

Front 29

periodic table

Back 29

a chart of the chemical elements arranged in rows of increasing atomic number so that the elements in each column (group) have similar chemical properties

Front 30

groups

Back 30

any of the vertical columns of elements in the periodic table

Front 31

periods

Back 31

the rows of elements in the periodic table

Front 32

alkali metals

Back 32

any of the elements in group 1 of the periodic table. All are metals that react readily with nonmetals to give ions with a +1 charge

Front 33

alkaline earths

Back 33

the elemeents in group 2 of the periodic table that all react readily with nonmetals to give ions a +2 charge

Front 34

noble gases

Back 34

any of the elements in group 18 of the periodic table that are all unreactive monatomic gases at room temperature and pressure

Front 35

halogens

Back 35

any of the elements in group 17 that all react readily with metals to give ions with a -1 charge

Front 36

metals

Back 36

any of the elements to the left of the zigzag line in the periodic table, can be hammered into thin sheets, pulled into wires, most are shiny, all except mercury are solids at room temperature

Front 37

nonmetals

Back 37

any of the elements to the right of the zigzag line, poor conductors of electricity, not shiny, not malleable, not ductible

Front 38

semimetals

Back 38

have properties between those of metals and nonmetals

Front 39

main group elements

Back 39

any of the elements in groups 1, 2 and 13-18

Front 40

essential element

Back 40

any of the 19 elements that are absolutely required in the diets of humans in order for them to survive