Elements & Substances Chemical changes

Substances Mixtures

Can be separated physically

Can be separated chemically

Stainless steel

Mercury sulfide

Granite

Mercury

Elements are the simplest forms of matter that can exist under normal laboratory conditions. They are the building blocks for all other substances. See periodic table, that’s where you’ll find them.

Compounds are formed when two or more elements combine with one another. They can only be separated by chemical means.

Each element is represented by a one or two letter chemical symbol. Most of the time, it is the first one or two letters of the element’s name. The first letter is always capitalized, the second is lowercase. Latin names account for some of the symbols not resembling their element’s name.

Elements are separated into groups based on a set of repeating properties.

H2OSymbol for hydrogen

Symbol for hydrogen

Symbol for

oxygen

Symbol for

oxygen

Subscript for

hydrogen

Subscript for

hydrogen

C12H22O11

Symbol for carbon

Subscript for carbon

Symbol for hydrogen

Subscript for hydrogen

Subscript for oxygen

Symbol for oxygen

Compounds can be broken down into simpler substances through chemical changes, but elements cannot.

Carbon + water vapor

Carbon + water vapor

SucroseSucrose

In a chemical reaction, one or more substances change into new substances.

The starting materials are called reactants and the substances formed are called products.

CH4 + O2 CO2 + H2O

The ability of a substance to undergo a chemical reaction and to form new substances is called a chemical property. Words such as rust, rot, decompose, ferment, explode, and corrode usually signify a chemical change.

Color change – hamburger browns in a skillet

Odor change – milk sours Solid formed – two liquids are poured

together and a solid forms, not and I mean definitely not water freezing to form an ice cube. That is a physical change people.

Energy change – gets hot or cold Gas evolved – the fizz of an antacid

tablet.

The law of conservation of mass – in any physical or chemical change, mass is neither created nor destroyed; it is conserved.