Chemistry Definitions - Grade 3

Front 1

Chemistry

Back 1

the study of matter and the changes that take place with that matter

Front 2

Matter

Back 2

anything that has mass and occupies space - anything made up of atoms and molecules

Front 3

Atom

Back 3

the basic building blocks of all things - they are what elements are made of

Front 4

Nucleus

Back 4

the center of an atom. It contains the subatomic particles protons and neutrons

Front 5

Protons

Back 5

positively charged (+) subatomic particles in the nucleus of an atom

Front 6

Neutrons

Back 6

subatomic particles in the nucleus of an atom that have no charge

Front 7

Electrons

Back 7

negatively charged (-) subatomic particles that spin around the nucleus of an atom

Front 8

Quark

Back 8

a particle of matter - they combine in various ways to form atoms

Front 9

Ions

Back 9

this is a word for atoms and molecules that contain a charge

Front 10

Positive Ions

Back 10

ions that have more protons than electrons

Front 11

Negative Ions

Back 11

ions that have more electrons than protons

Front 12

Elements

Back 12

A substance that cannot be broken down by chemical means. They are defined by the number of protons they possess.

Front 13

Periodic Table of Elements

Back 13

A chart that organizes all the known elements in order from left to right and top to bottom in order of increasing atomic number (the number of protons they possess)

Front 14

Chemical reaction

Back 14

a chemical change which forms new substances - can involve changing one molecule into a different molecule or breaking one molecule down into smaller molecules, atoms, or ions

Front 15

Molecule

Back 15

a group of two or more atoms that stick together

Front 16

Water

Back 16

a molecule which is the combination of hydrogen and oxygen atoms

Front 17

Polymers

Back 17

giant molecules made up of many molecules all strung together to form really long chains (and sometimes more complicated structures too)

Front 18

Materials

Back 18

items you need to do an experiment

Front 19

Procedure

Back 19

the steps you do during an experiment

Front 20

Observations

Back 20

what you see during an experiment

Front 21

Discussion

Back 21

explains what your observations of an experiment tell you about atoms and molecules

Front 22

Mixture

Back 22

two or more substances which do not change when combined - they can be separated again - they remain what they are

Front 23

Compound

Back 23

a new substance formed when two or more atoms join together in a chemical reaction

Front 24

Colloid

Back 24

A type of mixture in which the substances mixed together don't settle out.

Front 25

Solid

Back 25

a state of matter in which the molecules of a substance have been packed close together - it is usually hard and retains its shape

Front 26

Liquid

Back 26

a state of matter in between solid and gas - it takes the shape of the container it is in, and likes to stay together (the molecules are "sticky")

Front 27

Gas

Back 27

a state of matter in which the atoms are widely spread out and bounce around constantly

Front 28

Physical Change

Back 28

When a substance changes but keeps the same identity

Front 29

Chemical Change

Back 29

When substances change to form new substances

Front 30

Groups (Periodic Table)

Back 30

The columns in the Periodic Table. They contain the same number of electrons in the outer shell.

Front 31

Periods

Back 31

The rows in the Periodic Table. They tell you how many electron shells an element has.

Front 32

Relative Atomic Mass

Back 32

The average mass number of the atoms in a sample of an element. The mass number is the total number of protons and neutrons in a nucleus.

Front 33

Atomic Number

Back 33

The atomic number is the number of protons in the nucleus of an atom. It is unique for each element and is usually designated by a subscript to the left of the elemental symbol.

Front 34

Chemical Symbol

Back 34

A one or two letter notation for one of the elements in the periodic table. (Examples: H is the chemical symbol for Hydrogen, Na is the chemical symbol for sodium.)

Front 35

Similar Behavior of Elements

Back 35

Elements that behave in more-or-less similar ways are sometimes grouped together by shading them a certain color on the table. Examples of such groupings are: non-metals, semi-metals, metals, transition metals, and inner-transition metals.