Elements & Substances Chemical changes. SubstancesMixtures Can be separated physically Can be...
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Transcript of Elements & Substances Chemical changes. SubstancesMixtures Can be separated physically Can be...
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.