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Chapter 3: Elements combine to f o r m compounds

Gra d e 9 S cien c e: Unit 1: A t oms, Elements, a n d Co m pounds. Chapter 3: Elements combine to f o r m compounds. Co m pounds  A pu r e su b stance made of t w o or mo r e kinds of elements combined in fi x ed p r opo r tion s .  Rep r ese n ted b y a c hemical

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Chapter 3: Elements combine to f o r m compounds

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  1. Grade9Science: Unit1:Atoms,Elements,andCompounds Chapter3:Elements combine to formcompounds

  2. Compounds Apuresubstance made of twoormorekindsofelementscombinedinfixed proportions. Representedbya chemical Chemicalbondshold them formula. together. Areeither ionic or covalent.

  3. Modelof HCl( hydrochloricacid)

  4. CovalentCompounds Atoms combine by sharing electrons to form molecules. Molecules:a group ofatoms held togetherbysharing oneor more pairsof electrons. Examplesincludecarbon dioxideand water.

  5. Formedfrom non-metals only. They do not conduct electricity. Maybea solid,liquid,or gasat roomtemperature.

  6. MethaneCH4

  7. H C H C H H H

  8. Examplesof Compounds Tablesugar Covalent C12H22O11 CO2 H2O CH4 Carbon Dioxide Water Methane

  9. IonicCompounds Atomsgain or loseelectrons to formions. All the the the positiveions attractall negativeions everywherein samecrystal. Formedfrom metalsand non- metals.

  10. Allaresolid atroom temperature. Highmelting Willconduct and boiling points. electricitywhen meltedor dissolvedin water. Arealso called“salts”.

  11. MagnesiumChlorideMgCl2

  12. Examplesof IonicCompounds NaCl SodiumChloride CaCO3 CalciumCarbonate Na2SO4 SodiumSulfite NaOH SodiumHydroxide

  13. NamingCompounds Everycompound has a... Name:indicatestheelements present in thecompound Formula:indicatesthe symbolsand ratio ofeach elementpresentin the compound. 1. 2.

  14. Rulesfor NamingCompounds IonicCompounds Seepage81-2 CovalentCompounds Seepage83 Completepracticeproblems pages82 &83 on

  15. Physical & Chemical Changes PhysicalChanges: theappearanceof mayhavechanges holdingtheatoms a substance but the bonds together in molecules and ions havenot been brokenand no newbondshave been made.

  16. Includes: allchangesin state(melting, evaporation, freezing) Dissolving Cutting condensation, Tendto beeasy to reverse.

  17. ChemicalChanges: Producenew substances with newproperties;mayor benoticeable. Newbondsareformedothersarebroken. maynot while

  18. Chemicalequations can be writtenfor allchemical changes. For example thecomposition of water.

  19. Inachemical reactionthemass ofthe reactants= themassof the products. Theelementsare conserved but not the compounds. Ex.Corrosion,fruit ripening, combustion

  20. EvidenceofaChemical Change: Colorchange Heat,light,soundorconsumed 1. 2. produced Gasbubbles released Aprecipitateformed Difficultto reverse 3. 4. 5.

  21. Applicationsof Chemical Changes Harnessing Combustion amountsof combustion releaseslarge energy which canbe usedtoprovideheatand light, electricaland mechanical energy.

  22. Solvingthecorrosionproblem (aprocessby whichmetals combinewithoxygen;oxidation) Usingchemicalchange for traditionalproducts (example:tanning hides,making dyesand medicinesfrom plants, andpreservingfood)

  23. Core LabActivity 3-3C pg. 92-3 ObservingChangesin Matter

  24. CORE STSE: “Plasticsand ModernLife”

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