chemistry chapter 2
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Chemistry Chapter 2 . Changes in Matter Physical and Chemical Changes. Types of changes in matter:. Physical Change. Chemical. Physical change alters the form of a substance but does not change it to another substance. The substance has the same properties as the starting material - PowerPoint PPT PresentationTRANSCRIPT
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Changes in MatterPhysical and Chemical Changes
Chemistry Chapter 2
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Physical ChangePhysical change alters
the form of a substance but does not change it to another substance. The substance has the same properties as the starting materialTearing paper, bending
a nail, spinning wool into yarn
When a substance undergoes a chemical change, it is changed into a different substance with different propertiesBurning wood turns
it into carbon dioxide and ash
Types of changes in matter:Chemical
Both changes involve energy!!
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Changes in matter involve energy:Every substance contains energy from the movement of its particles called THERMAL ENERGY
The higher the temperature of a substance, the greater its thermal energy.
Another form of energy comes from the chemical bonds within matter : CHEMICAL ENGERY
Matter changes whenever energy is added or taken away!
The LAW OF CONSERVATION OF ENERGY states that in every physical change and chemical change the total amount of energy stays the same.
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MeltingChange in state from a
solid to a liquidIce cube melting –
energy to melt comes from the air in room. Added thermal energy makes the water molecules vibrate faster, which raises their temperature. Eventually water molecules vibrate so fast they break free from their position in ice crystals.
Click for melting chocolate video
Click for melting gold video
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FreezingChange in state from a
liquid to a solidWater turns to ice –
when water is placed in the freezer the water loses energy to the cold air in the freezer. Water molecules move more slowly. When the temperature reaches 0°C, the molecules are moving so slowly that they form regular patterns which form ice.
Water freezing video (click ice cube tray)
Click for video
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CondensationChange in state from
a gas to a liquidOccurs when a gas
loses enough thermal energy to become a liquidClouds, breath on a
mirror, fog, steam
Condensation video (click on glass)
Condensation on soda can
Condensation on window
Condensation on mirror
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EvaporationWhen vaporization
takes place only at the surface of the liquidA puddle drying up
after a rainstormBeads of sweat
evaporate off your skin
When vaporization takes place inside the liquid as well as at the surfaceWater boiling on stove
Vaporization – change in state from a liquid to a gasOccurs when a liquid gains enough energy to become a gas
Boiling
Click for videoClick for video
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SublimationChange in state from a
solid to a gasOccurs when a solid
gains enough energy to become a gas. Particles DO NOT pass through the liquid state at all.Dry ice, moth balls,
snow on a cold day
Sublimation of Dry ice(click to watch video)
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http://itl.chem.ufl.edu/2045_s00/lectures/lec_f.html
Changes in state
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Changes of State
http://itl.chem.ufl.edu/2045_s00/lectures/lec_f.html
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One substance breaks down into two or more other substances
or Two or more substances combine forming one
or more new substances.
NEW SUBSTANCES ARE PRODUCED
Chemical Changes (Chemical Reaction)
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Signs of chemical reactionsBubbles (gas produced)Light producedColor changeSolid (precipitate) formedOdor changeHeat
Signs of a chemcial reaction
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Baking soda and vinegarhttp://www.youtube.com/watch?v=nrTpubja0z8
Sodium Chloridehttp://www.youtube.com/watch?v=Ftw7a5ccub
s&feature=related
Examples of chemical changes….
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Mentos and diet coke http://www.youtube.com/watch?v=LjbJELjLgZg&f
eature=related
Is this a chemical or physical change?
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Has properties of both solid and liquidExamples: Oobleck, PVA slime, and silly putty
Non-Newtonian Fluids
Click for video