chapter 1- introduction to matter. matter the “stuff” that makes up everything in the universe....
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MATTER• The “stuff” that makes up everything in
the universe.
• It has a variety of properties (characteristics)
• These characteristics can be used to identify substances.
• Each specific substance has its own combination of properties that can be used to identify it.
• Chemistry is the study of matter and how matter changes
• Elements are represented by symbols
• One or two letters, first letter ALWAYS capitalized
• Oxygen-O Aluminum- Al
• Hydrogen-H Gold-Au
• Mercury-Hg Sodium-Na
COMPOUNDS• Elements can exist uncombined or combined.• A compound is a substance made of two or
more elements in a specific ratio• Compounds are represented by formulas • A formula shows the ratio of elements in the
compound• Ex. H2O, CO2, NaCl
• Mixtures are made of two or more substances-elements, compounds, or both, that are together in the same place but are not chemically combined.
• Ex. Salt water, air, soup, salad
Compound vs. mixture?
• Substances in mixtures keep their individual properties. Ex. Chex mix
• Substances in compounds change their individual properties Ex. NaCl (salt)
Changes in Matter
• Physical changes alter the physical appearance but do not turn material into a new substance
• Changes in :
• Ex. Water melting, freezing, evaporating
• The water looks different, but it is still H2O
Chemical Changes
• Chemical changes or chemical reactions, change matter into new substances
• The change is permanent
• Ex. Burning paper, baking a cake, metal rusting
Volume• The amount of space an object
occupies.
• To measure a rectangular object:V= Length x Width x Height
• A small block of wood floats on water. It has a volume of 2 cubic centimeters and a mass of 20 grams. What is the density?
Early ideas about atoms• Democritus-Greek
philosopher, lived about 440 B.C.
• He called the smallest piece of a substance “atomos”, Greek for “uncuttable”
John Dalton-1802
• Proposed atomic theory
• Imagined atoms to be like tiny marbles that are impossible to break
• In any element, all the atoms are exactly alike
• Atoms of different elements are different
• Atoms of two or more elements can combine to form compounds
• Atoms of each element have a unique mass
• The masses of the elements in a compound are always in a constant ratio
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