Chemical PropertiesSection 17.3

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Demo - Candle• What physical changes can be made to

each item?– Candle– Match– Stick

• Light the match and put it near the side of the candle. Is the melting wax a physical or a chemical change?

• Light the candle. As the wax and the wick burn, is it a physical or a chemical change?

Chemical Properties of Matter• Chemical properties describe a substance’s ability

to change into new matter with new properties.

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– Flammability: describes whether substances will react in the presence of oxygen and burn when exposed to a flame

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Chemical Properties– Reactivity: describes the ability of two

or more substances to combine to form one or more new substances.• Rusting – reactivity with oxygen• Explosive reaction of elemental

sodium with chlorine to form table salt

Realplayer videos\Bill Nye The Science Guy on Chemical Reactions (Full Clip) - Bing Videos.flvRealplayer videos\Reaction of Sodium Chlorine (with subtitles).flv

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Chemical Property Applications• Galvanized steel is steel coated with

zinc to prevent rusting (buckets, nails).

• Steel plated with tin was once used in food cans and containers. Today, aluminum cans have replaced most steel cans.

Interesting Facts• Before the early 1960s, there was

a group of gases (named noble gases) that were thought to be unreactive. However, in 1962, Dr. Neil Bartlett of Univ. of Brit. Columbia formed a new compound by combining platinum, fluorine, and the noble gas xenon.

• In 2002, chemists created new compounds by bonding uranium with argon, krypton and xenon (all noble gases).

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Interesting Facts• Chromium has been used

as a coating on car bumpers because it is nonreactive with oxygen (so the bumper is protected from rusting).

• Rustproofing involves treating the car’s underside and panels with sealants, which penetrate the seams, cracks, and holes to keep out air and moisture – which would increase the rate of rusting.

Substance Identification• Characteristic properties are used to

identify and classify substances. They can include both physical and chemical properties. Examples: density, solubility, flammability, reactivity

• These properties do not depend upon the size of the sample (so mass, weight and volume would not be characteristic properties).

Substance Identification• Example: How can you tell the

difference between baking soda and baking powder if they are out of their container?

• Reactivity with vinegar:– Baking soda reacts– Baking powder does not

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Chemical Changes• Chemical changes are

the processes by which one or more substances are changed into new substances.

Indicators of Chemical Change

• Change in color or scentRealplayer videos\Chemical Changes color change.mov• Production of a gas – fizzing,

foaming, effervescence.Realplayer videos\Chemical Changes gas production.mov

Indicators of Chemical Change• Production of a solid (precipitate)Realplayer videos\Precipitate formation Chemistry Comes Alive!.mov

• Production of heat• Production of light or soundRealplayer videos\Heat released in chemical reactions Chemistry Comes Alive!.mov

• What indications of chemical change do you see in the next video?

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Chemical Changes• Matter’s identity is changed in a

chemical reaction. • Reversing a chemical reaction (getting

back what you started with) is not always possible. If it is possible, it requires more chemical changes to take place.

• Could you reverse the explosion of fireworks?

Physical Changes• Since physical changes don’t change the

composition of a substance, they are frequently easily reversible.

• Example: Heating an ice cube to make it melt e cool the resulting liquid to make it freeze

• Dissolving a solid in a liquid e making the substance recrystallize from the solution

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References:• http://www2.chemistry.msu.edu/portraits/PortraitsHH_Detail.asp?HH_LName=BartlettN• http://www.kenyacarbazaar.com/blog/?p=899• http://carondelet.net/Aspring08/Project2/Caitlin/New%20York%20City.htm• http://www.artmetal.com/images/sculpture_gallery/josh/2007/07/rusted_sculptures_update_0• http://www.manufactum.com/Artikel/99272/2GalvanizedSteelPlantTub.html• http://besbryant.sharpschool.com/cms/One.aspx?portalId=839802&pageId=2630106• http://mbt6644.k12.sd.us/frontpage1/project1/inthelab1/pictures.htm• http://miamirealestatecafe.com/2009/12/28/cleaning-tips-for-your-miami-home-using-everyday-items• http://www.bbc.co.uk/food/baking_powder• http://www.etftrends.com/2010/07/price-impact-aluminum-etf/• http://www.icollector.com/Lot-Of-7-Tin-Cans-Texaco-Capella-Oil-Tin-Can-Transmi_i8458786• http://qwickstep.com/search/chemical-changes-examples.html• http://www.chemistryland.com/CHM130W/04-Properties/PropertiesBook/ChangesAssignment.htm• http://www.queenmaryschool.net/ScienceFair/?tag=/chemical-change• http://picsdigger.com/keyword/chemical%20changes/• http://jchemed.chem.wisc.edu/JCESoft/CCA/pirelli/pages/cca1NaIHgCl2.html• http://www.treklens.com/gallery/North_America/Canada/photo154072.htm• http://micro.magnet.fsu.edu/moviegallery/chemicalcrystals.html