AP Chemistry Introduction

matter: anything having mass and volume mass: weight: volume: units: L, dm 3, mL, cm 3 state of matter: the amount of matter in an object the pull of gravity on an object the space an object occupies solid, liquid, or gas conversions: 1 L = 1 dm 3 ; 1 mL = 1 cm 3 atom: a basic building block of matter -- ~100 diff. kinds

Elements contain only one type of atom. (a) monatomic elements consist of “unbonded,” identical atoms e.g., (b) polyatomic elements consist of several identical atoms bonded together -- diatomic elements: -- others: Fe, Al, Cu, He H 2 O 2 Br 2 F 2 I 2 N 2 Cl 2 P 4 S 8 “7 7 7” Broken Dreams Blvd.

(c) allotropes: different forms of the same element in the same state of matter OXYGEN CARBON oxygen gas ozone elemental carbon graphite diamond buckyball (O 2 ) (O 3 )

molecule: a neutral group of bonded atoms Description Chemical Symbol Model 1 oxygen atom 1 oxygen molecule 2 unbonded oxygen atoms 1 phosphorus atom 1 phosphorus molecule 4 unbonded phosphorus atoms O O2O2 2 O P P4P4 Elements may consist of… either molecules or unbonded atoms. 4 P

Chemical symbols for elements appear on the periodic table; only the first letter is capitalized. He Ne Ar Kr Xe Rn 86 (222)

Compounds contain two or more different types of atoms. -- have properties that differ from those of their constituent elements e.g., Na (sodium): Cl 2 (chlorine): explodes in water poisonous gas table salt (NaCl)

Every sample of NaCl tastes the same, melts at the same temp., and is 39.3% Na and 60.7% Cl by mass. Compound Composition All samples of a given compound have the same composition by mass.

A 550. g sample of chromium(III) oxide (Cr 2 O 3 ) has 376 g Cr. How many grams of Cr and O are in a 212 g sample of Cr 2 O 3 ? 68.4% Cr % Cr = and 31.6% O Cr: O: 212 g (0.684)= 145 g Cr 212 g (0.316)= 67 g O chromium(III) oxide (New sample has same composition.)

composition: copper: water: Properties Chemistry tries to relate the microscopic and macroscopic worlds. what the matter is made of many Cu atoms many “threesomes” of 2 H’s and 1 O describe the matter. e.g., what it looks like, smells like, how it behaves

States of Matter LIQUIDSOLIDGAS ( ( ) ) vibrating translating; close together translating quickly; far apart vapor:the gaseous state of a substance that generally is found as a solid or liquid

Changes in State Energy put into system: Energy removed from system: LIQUIDGASSOLID freezing condensation deposition sublimation boilingmelting

Classifying Matter (Pure) Substanceshave a fixed composition and fixed properties. ELEMENTS COMPOUNDS e.g., Fe, N 2, S 8, UH 2 O, NaCl, HNO 3 -- they have a single chemical formula sulfur (S 8 )sodium chloride (NaCl)

Mixtures contain two or more substances mixed together. -- have varying composition and varying properties -- The substances are NOT chemically bonded; they retain their individual properties. Tea, orange juice, oceans, and air are mixtures.

Two Types of Mixtures homogeneous: (or solution) sample has same composition and properties throughout; evenly mixed at the particle level e.g., alloy: a homogeneous mixture of metals e.g., Kool Aid bronze (Cu + Sn) brass (Cu + Zn) pewter (Pb + Sn) salt water

Two Types of Mixtures (cont.) heterogeneous: different composition and properties in the same sample; unevenly mixed e.g., suspension: settles over time e.g., tossed salad raisin bran paint snow globes

MATTER Chart for Classifying Matter PURE SUBSTANCEMIXTURE ELEMENT COMPOUND HOMOGENEOUS HETEROGENEOUS

Separating Mixtures involves physical means, or physical changes. 1. sorting: 2. filtration: by color, shape, texture, etc. by particle size -- No chemical reactions are needed because… substances are NOT bonded.

Separating Mixtures (cont.) 3. magnetism: 4. chromatography: one substance must contain iron some substances dissolve more easily than others

Separating Mixtures (cont.) 5. density: “sink vs. float”; perhaps use a centrifuge decant: to pour off the liquid blood after high- speed centrifuging

heat source thermometer water in (cooler) water out (warmer) more-volatile substance mixture condenser more-volatile substance, now condensed (i.e., the one with the lower boiling point) Separating Mixtures (cont.) 6. distillation: different boiling points Volatile substances evaporate easily.