Download - Compunds Ch4.2 8th PDF
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Chapter 4 Section 2
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Objectives Explain how elements make up compounds
Describe the properties of compounds
Explain how a compound can be broken down into itselements
Give examples of common compounds
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Compounds: Made of Elements Most elements take part in chemical changes fairly
easily
Elements are rarely found alone in nature
Elements combined chemically with other elements
form compounds
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Compounds continuedA particle of a compound is called a molecule
Molecules of compounds form when atoms of 2 ormore elements join together
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Water (H20)
http://sayee.ca/image/water%20molecule.gif
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Properties of Compounds Each compound has its own physical and chemical
properties
Ex: hydrogen peroxide (H202) Why are hydrogen peroxide bottles opaque (dark
brown)?
http://www.passionatehomemaking.com/wp-content/uploads/2009/04/fam_hydrogen_peroxide_pint-4080.jpg
http://www.umesc.usgs.gov/aquatic/drug_research/hydrogen_peroxide/hydrogen_peroxide_structure_400.gif
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Properties:
Compounds vs. Elements Properties of compounds differ from elements they are
formed from
Ex: Table salt (NaCl)
Sodium reacts violently with water
Chlorine is a poisonous gas
Combined chemically, they are safe to eat! Dissolves in water without exploding
http://www.usavsus.info/Images6/S070327-02L.jpg
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Breaking Down Compounds Some compounds can be broken down by chemical
changes into simpler compounds or elemental form
Ex: Carbonic acid (gives soda its fizz)
When the can is opened, carbonic acid breaks down into
Carbon dioxide (C02) and water (H2O)
Co2 and H2O can be broken down further into theelements (C, H, O)
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Methods of Breaking Down
Compounds
Add energy
Heat energy
Electric current
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Compounds in your World In industry:
Aluminum (makes cans & airplanes)
Not found alone in nature
Aluminum Oxide (Al2O3) broken down
Ammonia (make fertilizers)
Combining elements nitrogen and hydrogen (NH3 )
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Compounds in Nature Proteins found in all living things
Nitrogen
Carbon dioxide (C02) important roles in life Carbon, Oxygen
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Quick Quiz
Compounds cannot be broken down by any means
(True/False?)
Compounds can be broken down only by chemicalchanges (True/False?)
Heating can break down some compounds(True/False?)