Classification of Matter

Transcription

1 Classification of Matter

2 What is Matter? n Anything that has mass and occupies space (volume) n Composed of atoms n Exists in three states on earth: solid, liquid, gas n Exists in fourth state in space: plasma similar to gases except it consists consists of free electrons and ions -ionization of a gas can be caused by heating or electricity

3 Atoms- Extremely small building blocks of matter Ø Atoms cannot be broken down into smaller pieces by chemical means Ø The smallest distinct units in a sample of matter 10/4/17 3

4 Changes in State 10/4/17 4

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6 Classfication Flowchart MATTER yes Can it be physically separated? no yes Homogeneous Mixture (Solution) MIXTURE Is the appearance uniform? Heterogenous Mixture no yes PURE SUBSTANCE Compound Can it be chemically decomposed? Element no Colloids? Suspensions?

7 n Pure Substance: a particular kind of matter with a definite, fixed composition n Elements (copper, gold, oxygen) n Compounds (sugar, salt, water) n Mixture: a blend of two or more pure substances n Substances NOT chemically combined

8 A. Element Pure Substances n composed of identical atoms n Eg: copper wire, aluminum foil 10/4/17 8

9 Elements n Classification n n n Metal Nonmetal Metalloid

10 n Metals: Elements n Usually solid at room temp n Good conductors of heat and electricity n High luster (shiny) n Ductile easily pulled into wires n Malleable easily beaten into thin sheets n High melting point; high density n Usually don t combine with each other n Readily combine with nonmetals

11 n Nonmetals: Elements n Solids (C, P, S, Se, I 2 ); Liquid (Br 2 ); Gases (all others) n Poor conductors of heat and electricity; no luster n Low melting point; low density n Will combine with each other (CO 2 ) n Will combine with metals or metalloids n Some found uncombined in nature (noble gases)

12 n metalloids Elements n Found near the stairstep line of the periodic table n Have properties of both metals and nonmetals n Some used for semiconductors in electronics n Eg: Silicon, Germanium

13 Ø Ø Molecule a combination of 2 or more atoms (same or different) that are covalently bonded. A molecule is the smallest particle of a substance which exhibits the physical and chemical characteristics of the substance. 10/4/17 13

14 SUGAR MOLECULE WATER MOLECULE NITROGEN MOLECULE OXYGEN MOLECULE 10/4/17 14

15 Diatomic Molecules n Always exist as 2 atoms n 7 naturally occurring n Hydrogen, oxygen, fluorine, bromine, iodine, nitrogen, chlorine n H 2, O 2, F 2, Br 2, I 2, N 2, Cl 2 n Memory tool HOFBrINCl pronounced Hoffbrinkle

16 Demo: Electrolysis of Water, Decomposition of hydrogen peroxide 10/4/17 16

17 B. Compound n composed of 2 or more elements in a fixed ratio n properties differ from those of individual elements n Eg: table salt (NaCl) 10/4/17 17

18 Compounds n Two or more elements chemically combined n New properties n Definite proportions n Can be chemically/electrically separated n Molecular (covalent) or Ionic

19 Examples: H 2 O CO 2 CaSO 4 Na 2 O HBr KOH H 2 CO 3 10/4/17 19

20 Compounds Slight differences in combinations of atoms can have large difference in properties H 2 O- water, H 2 O 2 hydrogen peroxide C 2 H 6 O ethanol, drinkable C 2 H 6 O 2 ethylene glycol, poisonous 10/4/17 20

21 n For example Two different compounds, each has a definite composition. 10/4/17 21

22 Compounds n Law of Definite Composition n A given compound always contains the same, fixed ratio of elements. n Law of Multiple Proportions n Elements can combine in different ratios to form different compounds. 10/4/17 22

23 Compounds n Molecular/Covalent n Held together with covalent bonds in which electrons are shared n Molecule: smallest uncharged individual unit of a molecular compound n Eg. Water, carbon dioxide

24 n Ionic Compounds n Ion: positively or negatively charged atom or group of atoms n Cation positive n Anion negative n Held together by ionic bond attraction between positive and negative charges

25 10/4/17 25

26 Pure Substances: Summary èsame kind of particles throughout èhave a unique & identifiable set of properties 10/4/17 26

27 Pure Substances: Summary n Elements n A substance that cannot be separated into simpler substances n Compound n Two or more elements combined through a chemical reaction n Can be decomposed into simpler substances by chemical changes, always in a definite ratio n Different properties than elements which compose it 10/4/17 27

28 Naming and Formula Writing n Ionic vs. covalent compounds: naming and formulas in a few classes 10/4/17 28

29 n Watch video Types of Mixtures 10/4/17 29

30 Types of Mixtures n Heterogeneous mixtures n Visibly different parts n Eg. Chocolate chip cookies; granite n Two or more phases (usually) n Homogeneous mixtures n Different parts not visible (uniform throughout) n One phase n Eg. Sea water, air 10/4/17 30

31 Particle size distinguishes homogeneous solutions from other heterogeneous mixtures. 10/4/17 31

32 Homogeneous Mixtures Also known as solutions wvery small particles ( nm) èthe size of atoms or molecules - too small to be seen Tyndall Effect wno Tyndall effect (particles don t scatter light) wparticles don t settle weg: rubbing alcohol, air, brass (alloy) 10/4/17 32

33 TYNDALL EFFECT èis caused by reflection of light by very small particles in suspension in a transparent medium often seen from the dust in the air when sunlight comes in through a window seen when headlight beams are visible on foggy nights 10/4/17 33

34 Tyndall Effect 10/4/17 34

35 Colloids whomogeneous or heterogenous? Difficult to say wmedium-sized particles ( nm) (intermediate particle size between a solution and a suspension wtyndall effect wparticles don t settle weg: milk, shaving cream, hairspray, gelatin, agar, styrofoam 10/4/17 35

36 Suspensions wlarge particles (>1000 nm) wtyndall effect wparticles settle weg: fresh-squeezed lemonade, tomato juice, muddy water 10/4/17 36

37 ömechanical Mixture w Several components mixed and visible w Eg: Raisin Bran, pizza, granola, gravel 10/4/17 37

38 n Make a Lava Lamp 10/4/17 38

39 STOP 10/4/17 39

40 Separating Mixtures n Do NOT cause chemical changes n Heterogeneous Mixtures n Filtration 10/4/17 40

41 Separating Mixtures n Homogeneous Mixtures n Distillation 10/4/17 41

42 Separating Mixtures n Homogeneous Mixtures n Chromatography 10/4/17 42

43 n Homogeneous Mixtures n Separating Mixtures Crystallization 10/4/17 43