Grade 2 Science: Classification of Substances and Chemical Formulas

A comprehensive vocabulary review of substances, chemical formulas, atomic arrangements, colors, and classifications from Grade 2 Science Worksheet No. 29.

Pure Substance

Matter consisting of a single type of substance with uniform properties, categorized into simple substances and compounds.

Mixture

Matter composed of two or more pure substances mixed together, with examples including sugar water, saline solution (sodium chloride solution), milk, air, and petroleum.

Simple Substance

A pure substance that consists of only one type of element.

Compound

A pure substance consisting of two or more different types of atoms chemically combined in a specific ratio of symbols and numbers.

Molecule

A group of atoms bonded together representing the smallest fundamental unit of a chemical compound or element that can take part in a chemical reaction.

Non-Metal Compounds

Compounds formed exclusively by non-metal elements, such as water ($H_2O$), carbon dioxide ($CO_2$), ammonia ($NH_3$), and hydrochloric acid ($HCl$).

Metal-Nonmetal Compounds

Compounds formed by the bonding of metal and non-metal elements, such as $NaCl$, $CuCl_2$, $Ag_2O$, $CuO$, $MgO$, $FeS$, $CuS$, $NaHCO_3$, and $Na_2CO_3$.

Metallic Luster

A characteristic shiny appearance exhibited by metals when they are polished.

Hydrogen ($H_2$)

A gaseous simple substance composed of molecules made of two hydrogen atoms ($H-H$).

Oxygen ($O_2$)

A gaseous simple substance composed of oxygen molecules.

Nitrogen ($N_2$)

A gaseous simple substance composed of molecules made of two nitrogen atoms ($N-N$).

Chlorine ($Cl_2$)

A gaseous simple substance composed of molecules made of two chlorine atoms ($Cl-Cl$).

Water ($H_2O$)

A molecular compound formed by hydrogen and oxygen.

Carbon Dioxide ($CO_2$)

A molecular compound formed by non-metal carbon and oxygen atoms.

Ammonia ($NH_3$)

A compound consisting of nitrogen and hydrogen non-metal atoms.

Hydrochloric Acid / Hydrogen Chloride ($HCl$)

A compound composed of hydrogen and chlorine ($H-Cl$).

Sodium Chloride ($NaCl$)

A colorless compound formed by metal sodium and non-metal chlorine ($Na-Cl$).

Silver ($Ag$)

A white-colored metallic element.

Copper(II) Chloride ($CuCl_2$)

A blue-colored compound formed by copper and chlorine in a structure model of $Cl-Cu-Cl$.

Copper ($Cu$)

A red-colored metallic element.

Silver Oxide ($Ag_2O$)

A black-colored compound consisting of silver and oxygen ($Ag-O-Ag$).

Copper Oxide ($CuO$)

A black-colored compound formed by copper and oxygen ($Cu-O$).

Magnesium Oxide ($MgO$)

A white-colored compound formed by magnesium and oxygen ($Mg-O$).

Iron Sulfide ($FeS$)

A black-colored compound formed by iron and sulfur ($Fe-S$).

Copper Sulfide ($CuS$)

A black-colored compound formed by copper and sulfur ($Cu-S$).

Sodium Hydrogen Carbonate ($NaHCO_3$)

A white-colored compound composed of sodium, hydrogen, carbon, and oxygen.

Sodium Carbonate ($Na_2CO_3$)

A white-colored compound composed of sodium, carbon, and oxygen.

Carbon ($C$)

A black-colored non-metal element formed by a large collection of gathered carbon atoms.

Sulfur ($S$)

A yellow-colored element formed by gathered atoms, which as an exception can also form molecules.