Chapter 2 Lecture Notes.docx - Chem 1035 Chapter 2 1 of 40...

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Chem 1035 Chapter 2 1 of 40Chapter 2The Components of MatterMATTERMixtures Pure SubstancesHomogenous Heterogenous Elements CompoundsCombine elements in ratios Ex: H20Hydrogen, Helium, Carbon*Elements are on the Periodic TableNon-UniformEx: Milk, Oil/WaterUniformEx: Saline 0.9% NaCl
Chem 1035 Chapter 2 2 of 40MIXTURESTwo or more substances that are physically combined Composition can vary (in terms of percentage, or in terms of molarity)Properties of the components are maintainedComponents can be separated physically (Filtering, Distilling)Heterogenous: Sand & H2OHomogenous: Air (78% N, 21% O)
Chem 1035 Chapter 2 3 of 40PURE SUBSTANCESElements: The simplest type of substance with unique chemical and physical properties. An element cannot be broken down into simpler substances. Elements consist of: Atoms: smallest particle of an element Molecules: two or more with the characteristics of that element. atoms bonded together.Elements That Occur As Molecules:COMPOUNDS
Chem 1035 Chapter 2 4 of 40
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Chem 1035 Chapter 2 6 of 40Atoms of one element (PURE)Diatomic molecules(PURE)Molecules of a compound (PURE)Mixture of two elements and a compound
Chem 1035 Chapter 2 7 of 40Mixture: separate iron from sulfur by magnetsCompound: Fe2+ S2-FeS
Chem 1035 Chapter 2 8 of 40Law of Definite Composition: A particular compound is always composed of the same elements in the same percent or fraction by mass.Mass Fraction: Mass of elementTotal mass of compound0.XXX is always less than 1 Percent by Mass: Mass of elementx 100Total mass of compoundH20
Chem 1035 Chapter 2 9 of 40CompositionMass FractionMass PercentFor a 25.00 gsample ofH2OH: 2.800 gO:H:O:H:O:For a 25.00 gsample ofH2O2H:O: 23.52 gH:O:H:O:Example Problem:What mass of hydrogen is in a 78.0 g sample of H2O?
Chem 1035 Chapter 2 10 of 40Law of Multiple Proportions: If elements A and B react to form two compounds, the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers.Using the values for H2O from page 8: element A is hydrogen and element B is oxygen:H2O: OH= H2O2: OH= John Dalton’s Atomic Theory 1807Elements are composed of tiny, indivisible particles called atoms (atomos, Greek for indivisible).
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