looking back key concepts summary a substance’s chemical and physical properties determine its...
TRANSCRIPT
LOOKING BACK
KEY CONCEPTS SUMMARY
• A substance’s chemical and physical properties determine its usefulness and effects.
– Physical properties (for example, state, colour, electrical conductivity) involve a
description of the substance as it is.
– Chemical properties describe a substance’s behaviour (for example, reactivity with
acids, combustibility) as it becomes a completely different substance(s).
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LOOKING BACK
KEY CONCEPTS SUMMARY
• Changes can be classified as chemical or physical.
– Chemical changes involve new substances being produced.
– Evidence of chemical change includes colour change, precipitate production, release
or absorption of energy, and formation of a gas.
– Physical change involves changes in form (for example, state) but not in chemical
identity.
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LOOKING BACK
KEY CONCEPTS SUMMARY
• We can classify pure substances by observing their properties.
– Elements can be grouped according to their properties.
– Metals and non-metals combine to form different kinds of compounds: ionic and
molecular.
– Compounds are pure substances that can be broken down into their individual
elements..
– Physical properties distinguish molecular compounds from ionic compounds.
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KEY CONCEPTS SUMMARY
• Ionic compounds are made up of positive and negative ions.
– Atoms gain or lose electrons resulting in a stable electron arrangement, thus
becoming ions.
– Positively charged ions are cations; negatively charged ions are anions.
– Ionic compounds consist of cations and anions linked by ionic bonds.
– Many ionic compounds are electrolytes: the solutions they form conduct electricity.
– The names of ionic compounds formed by two elements end in “ide.”
– The names of compounds that include polyatomic ions usually end in “ate.”
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LOOKING BACK
LOOKING BACKKEY CONCEPTS SUMMARY
• Molecular compounds are made up of distinct molecules.
– The majority of all known compounds are molecular.
– Molecules consist of two or more non-metal atoms linked by a covalent bond.
– Covalent bonds form when atoms share electrons.
– Molecular compounds are often named using prefixes.
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LOOKING BACKKEY CONCEPTS SUMMARY
• Many consumer products have been developed from petrochemicals.
– Product chemists select chemicals to perform specific functions in a product.
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Multiple Choice For each question, select the best answer from the four alternatives. 1. A chemical property is a a)characteristic that does not involve forming a new substanceb)behaviour that occurs when a substance becomes something newc)change that does not produce a new substanced)characteristic that involves forming a new substance 2. Halogens are relatively reactive elements becausea)they have full outer electron orbitsb)they react with other atoms in order to have a full outer electron orbitsc)they react with other atoms in order to have seven electrons in their outer electron orbitsd)they have empty outer electron orbits 3. In reactions with metals, non-metals tend toa)lose electrons to become positively charged anionsb)gain electrons to become negatively charged anionsc)gain electrons to become positively charged cationsd)lose electrons to become negatively charged anions
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4. Which of the following is the correct formula for potassium oxide?a)KOb)K2O2
c)K2Od)KO2 5. Which of the following is the correct formula for sulfur hexafluoride?a)SF5
b)S5Fc)SF6
d)S6F
Fill in the Blanks6. A(n) ___________________ is a vertical column of elements on the periodic table. 7. A(n) _______________ is an atom that has become negatively charged by gaining electrons.
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MatchingMatch each term on the left with the most appropriate term on the right.8. (a) F (i) ionic charge of –2
(b) Ga (ii) ionic charge of +3(c) K (iii) ionic charge of +2(d) O (iv) ionic charge of –1
9. (a) Ca3P2 (i) calcium phosphide
(b) Ca3(PO4)2 (ii) copper (I) chloride(c) CuCl2 (iii) calcium phosphate (d) CuCl (iv) copper (II) chloride
Short Answer10. Name the following compounds. a)Fe2O3
b)N2O4
c)MgOd)Na2SO4
11. Write the correct chemical formula for each compound.a)potassium phosphateb)carbon tetrachloridec)magnesium sulfided)lead (II) chloride
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