Classes of Pure Substances More About...
Transcript of Classes of Pure Substances More About...
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Basic Principles of Chemistry
Unit 2: Chemical Reactions and Their Significance
Lecture #9
Summary
• Matter...
– Is composed of atoms which...
• are composed of protons, neutrons, and electrons
• AND
• make up molecules
Classes of Pure Substances More About Matter
• Each pure substance is characterized by its own unique set of properties.
– Physical
– Chemical
Our Business
• The study of the physical and chemical properties of matter
Our Method
• The scientific method
• Making careful measurements and other observations
• Communicating our findings to others
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The Dilemma
• Atoms are very tiny
• Atoms are very numerous
Tiny Atoms
Many Atoms Counting by Weight
Counting Units
• Pair• Dozen• Gross• Score• Magnum• Ream• Turkey
Is This Really Necessary?
• Why do we need to be able to account for all the atoms and molecules in a sample?
• Can we account for all of the atoms or molecules in a sample?
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A New Counting Unit
• The MOLE
– One carbon (C) atomweighs 12.0 amu
– One mole of carbon (C)atoms weighs 12.0 g
Avogadro’s Number
• The MOLE
6.02 x 1023 items
This is HUGE!
Avogadro’s Number
• One mole of marbles could cover Earth to a depth of 50 miles.
Avogadro’s Number
• One mole of pennies could give every man, woman, and child on Earth $1,000,000,000,000!
Avogadro’s Number
• A glass of water contains about 10 moles of water.
• This is more water molecules than grains of sand in the Sahara Desert.
Extra Credit Assignment
• “How Big is a Mole” Project