Download Element - the simplest form of matter that can exist under normal

Academic Chemistry
Mr. Gensits
Class Notes 10/6/2009
Elements, Compounds, and Chemical Changes
Element - the simplest form of matter that can exist under
normal laboratory conditions
Elements are pure substances.
Elements cannot be separated into simpler substances by chemical
means.
Elements are the building blocks for all other substances
There are now 117 known elements (as of 2006).
All elements after uranium on the periodic table are man-made.
A compound is a chemical combination of two or more different
elements joined together in a fixed proportion.
Every compound has its own fixed composition.
Compounds are also pure substances.
A compound can be separated into simpler substances only by
chemical means.
Physical States of Matter
Solid, liquid, gas, plasma, and Bose-Einstein condensate
Volatile – substance changes to a gas easily at room temperature
Density – the amount of matter (mass) in a unit of volume
(another physical property)
Chemical Properties – can be observed only when there is a change
in the composition of a substance.
Describe the ability of a substance to react with other
substances or to decompose.
Chemical Change
The change of one or more substances into other substances
(involves a chemical reaction).
Evidence of Chemical Change
1. Evolution of gas.
2. Formation of a precipitate.
3. Production of heat or light.
4. Change in color.
Energy – the capacity to do work.
Exothermic reaction – gives off energy (usually as heat or light.)
Endothermic reaction – absorbs energy