1. Unit 2: Matter and Energy Chemistry

2. Matter Introductory Definitions matter: anything having mass and volume mass: weight: volume: units: L, dm 3, mL, cm 3 L3L3 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

3. composition: copper: water: properties: -- atom: a basic building block of matter what the matter is made of many Cu atoms many groups of 2 H’s and 1 O describe the matter what it looks like, smells like; its mass, temp., etc. how it behaves ~100 diff. kinds

4. Elements  contain only one type of atom 1. monatomic elements consist of unbonded, “like” atoms e.g., 2. polyatomic elements consist of several “like” 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”

5. 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 )

6. 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 O 2 2 O P P 4 Elements may consist of either molecules or unbonded atoms. 4 P

7.  Compounds …contain two or more different types of atoms …have properties that are different from those of their constituent elements Na (sodium): Cl 2 (chlorine): explodes in water poisonous gas table salt (NaCl)

8. Atoms can only be altered by _______ means. Molecules can be altered by ________ means. (i.e., chemical reactions, chemical changes) nuclear chemical e.g., Dehydration of sugar C 12 H 22 O 11 (s)  12 C(s) + 11 H 2 O(g) Electrolysis of water 2 H 2 O(l)  2 H 2 (g) + O 2 (g) Atomic blast at Hiroshima U Ba Kr neutron “bullet”

9. 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.

10. Classifying Matter (Pure) Substances…have a fixed composition …have fixed properties ELEMENTS COMPOUNDS e.g., Fe, N 2, S 8, UH 2 O, NaCl, HNO 3 Pure substances have a chemical formula. sulfur (S 8 )sodium chloride (NaCl)

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

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

13. 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 snowy-bulb gifts

14. Contrast… 24K GOLD14K GOLD 24/24 atoms are gold element pure gold 14/24 atoms are gold mixture of gold & copper Au homogeneous mixture Au + Cu

15. MATTER Chart for Classifying Matter PURE SUBSTANCEMIXTURE ELEMENT COMPOUND HOMOGENEOUS HETEROGENEOUS

16. Separating Mixtures …involves physical means, or physical changes 1. sorting: 2. filter: by color, shape, texture, etc. particle size is different

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

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

19. Separating Mixtures (cont.) 6. distillation: different boiling points 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)

20. No chemical reactions are needed to separate mixtures; substances are NOT bonded. dental amalgam

21. Density  how tightly packed the particles are Density = Typical units: g/cm 3 for solids g/mL for fluids m V D liquids and gases Glass: liquid or solid?

22. To find volume, use… 1. a formula water displacement V = l w h V =  r 2 h V = ? V final V init V object = V final – V init 2.

23. ** Density of water = The density of a liquid or solid is nearly constant, no matter what the sample’s temperature. 1.0 g/mL = 1.0 g/cm 3 Things that are “less dense” float in things that are “more dense.” D < 1 g/cm 3 Density of gases is highly dependent on temperature. D < 1 g/cm 3 D > 1 g/cm 3 D < 1 g/cm 3 (And things that are “more dense” sink in things that are “less dense.”

24.  Galilean Thermometer Problem On a cold morning, a teacher walks into a cold classroom and notices that all bulbs in the Galilean thermometer are huddled in a group. Where are the bulbs, at the top of the thermometer or at the bottom? 1. Bulbs have essentially fixed masses and volumes. Therefore, each bulb has a relatively fixed density. 2. The surrounding liquid has a fixed mass, but its volume is extremely temperature-dependent. D1D1 D2D2 D3D3 D4D4 D5D5

25. D1D1 D2D2 D3D3 D4D4 D5D5 3. The density of the liquid can be written as… so… …if the liquid is cold:…but if it’s hot: m liq = On a cold morning, where are the bulbs? AT THE TOP V liq m liq D liq = V liq D liq

26.  Density Calculations 1. A sample of lead (Pb) has mass 22.7 g and volume 2.0 cm 3. Find sample’s density. m V D 2. Another sample of lead occupies 16.2 cm 3 of space. Find sample’s mass. m = D V= 184 = 11.35 g V

27. 3. A 119.5 g solid cylinder has radius 1.8 cm and height 1.5 cm. Find sample’s density. 1.5 cm 1.8 cm m V D m V =  r 2 h =  (1.8 cm) 2 (1.5 cm) = 15.3 = 7.81 cm 3

28. Properties of Matter CHEMICAL properties tell how a substance reacts with other substances. PHYSICAL properties can be observed without chemically changing the substance. EXTENSIVE properties depend on the amount of substance present. INTENSIVE properties do not depend on the amount of substance. ONE OF THESE AND ONE OF THESE

29. States of Matter LIQUIDSOLIDGAS ( ( ) ) vibrating translating; close together translating quickly; far apart

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

31. Energy  the ability to do work potential energy: kinetic energy: -- e.g., stored energy stored in bonds between atoms in food, energy of motion wiggling, translating, and rotating of particles -- “hot” gas particles move faster, have more KE gasoline, batteries

32. Law of Conservation of Energy: 2 H 2 + O 2  2 H 2 O E after = E before +  + energy + WHOOF!

33. For the combustion of acetylene… PE reactants PE products KE stopper heat, light, sound ENERGY CO 2 + H 2 OC 2 H 2 + O 2 Energy is conserved.

34.  Energy Changes endothermic change: system absorbs heat exothermic change: system releases heat -- Choose “endo” or “exo.” water boiling paper burning steam condensing CO 2 subliming water freezing ice melting beaker feels cold beaker feels hot ENDO EXO EXO ENDO EXO ENDO

35. R P Energy endothermic exothermic R P Energy ACTIVATION ENERGY (most chemical reactions)(photosynthesis) CO 2 + H 2 O + sunlight  C 6 H 12 O 6 + O 2 C + O 2  CO 2

36. The Mole Atoms are so small, it is impossible to count them by the dozens, thousands, or even millions. To count atoms, we use the concept of the mole. 1 mole of atoms = That is, 1 mole of atoms = _________ atoms. The mole is the SI unit for “amount of substance.” 602,000,000,000,000,000,000,000 atoms 6.02 x 10 23

37. How Big is a Mole? …about the size of a chipmunk, weighing about 5 oz. (140 g), and having a length of about 7 inches (18 cm). I Meant, “How Big is 6.02 x 10 23 ?” BIG. 6.02 x 10 23 marbles would cover the entire Earth (including the oceans) …to a depth of 2 miles. 6.02 x 10 23 $1 bills stacked face-to-face …and back …7.5 million times. It takes light 9,500 years to travel that far. would stretch from the Sun to Pluto

38. For any element on the Periodic Table, one mole of that element (i.e., 6.02 x 10 23 atoms of that element) has a mass in grams equal to the decimal number on the Table for that element. He 2 4.003 Ne 10 20.180 Ar 18 39.948 Kr 36 83.80 Xe 54 131.29 Rn 86 (222) 1 mole of (i.e., 6.02 x 10 23 ) helium atoms has a mass of 4.0 grams. 1 mol Ne = 20.2 g 1 mol Ar = 39.9 g 1 mol Kr = 83.8 g 1 mol Xe = 131.3 g 1 mol Rn = 222 g

39. 1 mol = 6.02 x 10 23 particles MOLE (mol) Mass (g) Particle (atoms) 1 mol = molar mass (in g) Island Diagram