Elements & Substances Chemical changes
SubstancesMixtures Can be separated physically Can be separated chemically
Stainless steel Mercury sulfide Granit e 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.
H2OH2O Symbol for hydrogen Symbol for oxygen Subscript for hydrogen C 12 H 22 O 11 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 Sucrose
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. CH 4 + O 2 CO 2 + H 2 O 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.