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CH1010 Lecture 2

# Mixtures mixtures homogeneousmixturessolutions

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Unformatted text preview: ention to the placement of zeros. (b) 0.1044 g 4sf (e) 57,600. s 5.7600x104 s 5sf (c) 53.069 mL 5sf (f) 0.0000007160 cm3 4sf 7.160x10­7 cm3 SOLUTION: (a) 0.0030 L 2sf (d) 0.00004715 m 4sf 4.715x10­5 m Sample Problem 1.9 Significant Figures and Rounding PROBLEM: Perform the following calculations and round the answer to the correct number of significant figures: 1 g 4.80x104 mg 1000 mg 16.3521 cm2 ­ 1.448 cm2 (a) (b) 7.085 cm 11.55 cm3 PLAN: In (a) we subtract before we divide; for (b) we are using an exact number. (a) 16.3521 cm2 ­ 1.448 cm2 7.085 cm 4.80x104 mg 1 g 1000 mg = = 14.904 cm2 7.085 cm 48.0 g 11.55 cm3 = 2.104 cm SOLUTION: (b) 11.55 cm3 = 4.16 g/ cm3 Classification of Matter Classification of Matter Anything that occupies space and volume States of Matter­ 3 Solid­ rigid fixed volume and shape Liquid­ definite volume but no specific shape Gas­ no fixed volume or fixed shape The physical states of matter. Mixtures Mixtures Homogeneous Mixtures ­ Solutions Heterogeneous Mixtures Components cannot be distinguished visibly Can be solid, liquid or gas e.g. brass, wine, air Components can be distinguished visibly e.g. sand in water Pure Substances Pure Substances Substance with constant composition Homogeneous mixtures or solutions may contain many pure substances We call these pure substances compounds Compounds Compounds W ine a compl ex sol ut i on W e can use many t echni ques t o i sol at e each pur e subst ance and separ at e i t f r om t he mi x t ur e Etc. Ethanol C2H6O W ater H2O P ur e Subsances Al l w i t h const ant C omposi t i on E ach composed of El ement s C , H and O W e cal l each Pur e Subst ance a " Compound " G lucose C6H12O6 Brief History of Chemistry Brief History of Chemistry 400 BC Greeks­matter consists of 4 basic substances – fire, earth, water, air 1661 Boyle 1794 Lavoisier Law of Conservation of Mass Looks at relationship of pressure and volume Also postulates that substances are composed of elements (basic units) He put no limit on # of possible elements ~1800 Proust – Law of Definite Proportions Does careful experiments with O2 (names it Oxygen) Demonstrates combustion involves oxygen Demonstrates O2 supports life Carefully weighs reactants and products of various rxns MASS IS CONSERVED Compounds contain constant proportions of elements e.g. Copper Carbonate has 5.3 parts Cu, 4 parts O, 1 part C Dalt...
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