Forming New Substances Ch 14.1 8th
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Transcript of Forming New Substances Ch 14.1 8th
Chapter 14 Section 1
Objectives:
Describe how chemical reactions produce new substances that have different chemical & physical properties
Identify 4 signs that indicate that a chemical reaction might be taking place
Explain what happens to chemical bonds during a chemical reaction
Question of the Day?
What do baking bread, launching a space shuttle, and digesting food have in common?
Chemical Reactions:
A process in which one or more substances change to make one or more new substances
Chemical reactions around you…
Think about the chemical reactions that occur in school everyday….
Make a list
Consider this…
Carbon dioxide (CO2) Dissolved under pressure –
effervescence in carbonated beverages
Does not combust and is denser than air – used in fire extinguishers to smother flames
Dry ice (CO2 in its solid form) – cooling effect – it sublimates!!
Signs of Chemical Reactions: Gas formation (bubbles!)
Solid formation (precipitate)
Energy change (light, thermal, electrical…)
Color change
A Change of Properties:
Signs don’t guarantee that a chemical change has taken place
Formation of NEW substance with DIFFERENT properties is the key!
http://101science.com/images/beaker.gif
Bonds: Holding Molecules Together Chemical bond: force that hold 2
atoms together in a molecule
Chemical reactions require that original bonds are broken and new bonds are formed
http://www.blobs.org/science/chemistry/bond.gif
http://facstaff.gpc.edu/~pgore/PhysicalScience/covalent_bond_animation.gif
Breaking & Making Bonds:
Molecules are always in motion
They may bump into each other
With enough energy, bonds can be broken
Atoms can rearrange, and new bonds form
Molecules in Motion…
http://www.aquamem.com/molecular_modeling/DPB_Reaction_Pages/MCA_DMA986_movie_optimized_v1.gif
New Bonds, New Substances Sodium is a violently reacting metal Chlorine is a poisonous gas
Combined: Sodium chloride (NaCl) – table salt!
Completely harmless together…
Sodium:
The Periodic Table of Videos – University of Nottingham
http://www.periodicvideos.com/videos/011.htm
Chlorine:
The Periodic Table of Videos – University of Nottingham
http://www.periodicvideos.com/videos/017.htm
Reference:
Holt Science and Technology: Physical Science. New York: Henry Holt & Co, 2007. Print.