Chapter 2 Matter and Change p. 38

Transcription

1 Chapter 2 Matter and Change p. 38 Describing Matter Properties: 1) Extensive depends on amt of matter in sample - ex s. mass, volume, calories, magnetism 2) Intensive depends on type of matter, not amt. - Hardness, Density, B.P. - All samples of same substance have same intensive prop s. (same composition) 1

2 Identifying Substances Physical Properties- observed & measured w/o changing composition color, hardness, m.p., b.p. Chemical Properties- observed by changing comp of material ability to burn, decompose, ferment, react w/, etc. States of matter 1) Solid- cannot flow (definite shape & volume) 2) Liquid- definite vol - takes shape of container (flows) 3) Gas- w/o definite vol or shape & flows Vapor- gaseous but normally liquid or room temp water gas, or water vapor? 2

3 Three Main Phases page 41 States of Matter Solid Definite Volume? YES Definite Shape? YES Result of a Temperature Increase? Small Expans. Will it Compress? Not easily Liquid YES NO Small Expans. Not easily Gas NO NO Large Expans. YES 3

4 4 th state: Plasma - formed at hi temps; ionized phase of matter (Sun) Sublime Freeze Melt Condense Evaporate Solid Liquid Gas 4

5 Physical vs. Chemical Change Physical change changes visible appearance w/o changing comp of material Boil, melt, cut, bend, split, crack Is boiled water still water? Reversible, or irreversible Chemical change - change where new substance formed Rust, burn, decompose, ferment Section 2.2 Mixtures p. 44 Mixture - physical blend of 2+ components 1) Heterogeneous uniform in comp Choc chip cookie, gravel, soil 2) Homogeneous - same comp thruout (solutions) Kool-aid, air, salt water Every part keeps own prop s 5

6 Solutions - homogeneous mixtures Mixed molecule by molecule, so too small to see diff pts occurs btwn any state of matter: gas-gas; liquid-gas; gas-liquid; solid-liquid; solid-solid (alloys) Steel (Fe, Cr & Ni) Phase? phase describes any pt of sample w/ uniform comp of properties A homogeneous mixture consists of a single phase A heterogeneous mixture consists of two or more phases. Note Figure 2.6, page 45 6

7 Separating Mixtures Some by physical means: rocks & marbles, iron filings & sulfur (magnet) Differences in physical props used to separate mixtures Filtration - separates solid from liquid in hetero mix. (by size) Figure 2.7, page 46 Separation of a Mixture Distillation: takes advantage of different boiling pts. NaCl boils at 1415 o C H 2 O boils at 100 o C Mg boils at 1107 o C 7

8 Separation of a Mixture Components of dyes such as ink may be separated by paper chromatography. Forensic Ink Analysis Chromatography video Applications of Chromatography 2 Greek words: chroma "color" and graphein "to write" Biological labs: ID amino acids detects drugs in urine Environmental labs: ID contaminants in waste oil pesticides in groundwater test drinking water & test air quality Pharmaceutical companies prepare quantities of extremely pure materials. Food industry ID contaminants like aflatoxin naturally occurring toxin produced by fungus 8

9 Sec 2.3 Elements & Compounds p. 48 Substances are either: a) elements, or b) compounds Pure Substances Element Compound Simplest matter 1 type of atom Cannot be broken down Broken down by chemical methods different prop s than elements 2+ atoms chemically combined 9

10 Compounds v.s. Mixtures Compounds Mixtures Made of one kind of material Made of more than one kind of material Made by a chemical change Made by a physical change Definite composition Variable composition Which is it? Compound Element Mixture 10

11 Chemical Change A chemical change chg producing matter w/ diff. comp than original matter 1+ substances are converted into different substances. Heat & light often indicate chem chg Classification of Matter 11

12 Symbols & Formulas 118 elements 1-2 letter symbol 1 st letter CAP; 2 nd letter lowercase B, Ba, C, Ca Some names Latin Table 2.2, page 52 cmpds have formula H 2 O, NaCl, C 12 H 22 O 11 Sec 2.4 Chemical Rxns p. 53 Chemical Changes Chemical property - ability of substance to undergo specific chem change Fe + O = rust rusting - chem prop of Fe During chem chge comp of matter always changes 12

13 Chemical Rxns are When 1+ substances changed into new substances Reactants- start w/ Products- end w/ Products have NEW PROPS diff from reactants Arrow points from reactants to new products Recognizing Chemical Changes 1) Energy absorbed/released (temp changes hotter/colder) 2) Color changes 3) Gas production (bubbling, fizzing, or odor change; smoke) 4) precipitate forms - solid separates from solution (won t dissolve) 5) Irreversibility - not easily reversed Some ex s not chem boiling water bubbles, choc syrup in milk, etc. 13

14 Conservation of Mass During any chem rxn, product mass = reactant mass All mass accounted for: Burning wood results in products that appear to have less mass (ashes). CO 2 & H 2 O vapor Law of conservation of mass - Page g Original mass = g Final mass reactants = product 14