Unit 1: Organization of Matter

Question 1

Physical Change

Answer 1

does not alter the chemical composition or identity of the substance, only the form
ex: freezing, boiling, making/separating mixture

Question 2

EXCEPTION: a homogenous mixture is a _ change

Answer 2

physical AND chemical

Question 3

SPECIAL: sometimes physical processes involve the breaking of chemical bonds LIKE the dissolution of salt in water

Answer 3

breaks the bonds between ions, but also creates ion-dipole interactions between the water and ions

Question 4

Chemical Change

Answer 4

DOES alter the chemical composition or identity of a substance and makes new substances
ex: burning, digesting, rotting, rusting
*chemical chg = chemical rxn

Question 5

Pure substance

Answer 5

something that can NOT be broken down into simpler matter using physical methods
- two types: elements and compounds

Question 6

Most common elements in Earth’s crust (3)

Answer 6

Oxygen, Silicon, Aluminum

Question 7

Most common elements in human body (3)

Answer 7

Oxygen, Carbon, Hydrogen

Question 8

Diatomic elements

Answer 8

Br.I.N.Cl.H.O.F

Question 9

EXCEPTION: O and O3

Answer 9

Oxygen CAN float around by itself as monoatomic O, or even O3 = ozone

Question 10

Allotropes

Answer 10

Different structural forms of the same element
ex: O vs O2 vs O3

Question 11

Law of Definite Proportions

Answer 11

In samples of any chemical compound, the masses of the elements are always in the same proportion.
ex: in water, mass ratio of O to H is always 8:1

Question 12

CALCULATING: Percent Composition

Answer 12

1. find molar mass of compound/molecule
2. Divide MM of element by MM of cule
3. Multiply by 100%

Question 13

CALCULATING: Empirical Formula

Answer 13

1. if given percent, assume 100g sample, so % = g
2. Mass to moles of each element
3. Divide everything by smallest # of moles
4. If necessary, multiply to make whole #s
5. Answers = subscripts

Question 14

CALCULATING: Molecular Formula

Answer 14

1. Find Empirical Formula mass
2. Divide MM given by formula mass (BOYCE ON TOP)

Question 15

Heterogenous mixture

Answer 15

all components are visible, not distributed evenly
ex: trail mix

Question 16

Homogenous Mixture AKA Solution

Answer 16

components can NOT be distinguished from each other, appear as one substance, distributed evenly
ex: air or alloys

Question 17

Sedimentation

Answer 17

heterogenous: occurs naturally when solid substances are heavier than their solvent and deposit at the bottom of the mixture

Question 18

Decantation

Answer 18

a heterogenous mixture that has distinct layers can be separated by slowly pouring one of the layers into another container **risk of mixing

Question 19

Filtration

Answer 19

separates parts of a heterogenous mixture by pouring it through a filter; larger particles (residue) held in filter while smaller particles (filtrate) pass through

Question 20

Distillation

Answer 20

used to separate homogenous based on their different boiling points: solution is heated, substances with lower boiling points evaporate, pass through a tube where it cools and turns back to water in separate container

Question 21

CALCULATION: Elemental Combustion Analysis

Answer 21

compounds with C, H, and O (and possibly +), analyzed through combustion in a chamber
1. 27.29% C in CO2; 11.19% H in H2O
2. Multiply mass of CO2 by % C = mass of C
3. Multiply mass of H2O by % H = mass of H
4. Subtract C+H from total mass = mass of O
5. mass to moles etc. to find empirical formula

Question 22

CALCULATION: Avogadro’s Number (Na)

Answer 22

6.022 x 10^23 . . . particles/molecules/formula units

Question 23

Chemical equation symbols over arrows

Answer 23

triangle = heat added
metal (Pt, Fe, etc) = catalyst

Question 24

Evidence for a Chemical Reaction (5)

Answer 24

1. Evolution of light or heat
2. Temperature change to surroundings
3. Formation of a gas (bubbles or odor) other than boiling
4. Color change **DUE to formation of new substance
5. Formation of a precipitate **FROM reaction of two aqueous solutions

Question 25

3 possible products when aqueous solutions react

Answer 25

1. Precipitate 2. Water (check pH = 7) 3. Gases 4. COMBO of any above

Question 26

CALCULATION: Percent Yield

Answer 26

(Actual Yield divided by Theoretical/Calculated Yield) x 100%

Question 27

Haber Process

Answer 27

N2 (g) + 3H2 (g) --> 2NH3 (g)

Question 28

Oxidation Number rules (1-4)

Answer 28

1. Non-bonded and diatomic elements = 0 2. Group 1 Metals in compound = +1; Group 2 Metals in compound = +2 3. F in compounds = -1; other halogens as long as most electronegative in compound = -1 4. H in compounds = +1; **WITH G1 or G2 Metal = -1

Question 29

Oxidation number rules (5-7)

Answer 29

5. O = -2; **WITH F = +2; **IN PEROXIDE (metal2O2) = -1 6. Sum of all oxidation numbers in a compound = 0 7. Sum of all oxidation numbers in polyatomic = charge on the polyatomic ion

Question 30

EXCEPTION: writing half-reactions

Answer 30

do NOT include elements that did not change oxidation numbers (spectator ions)

Question 31

Reduction Half-reaction Oxidation Half-reaction

Answer 31

KClO3 + 6e- --> KCl 3HNO2 --> 3HNO3 + 6e-

Question 32

CALCULATION: REDOX reactions in Acidic solutions

Answer 32

1. write separate half-reactions 2. balance everything but O and H 3. balance O and H by adding H2O 4. equalize electrons transferred 5. add half-reactions and cancel 6. check elements and charges are balanced

Question 33

CALCULATION: REDOX reactions in Basic solutions

Answer 33

1. write separate half-reactions 2. balance everything but O and H 3. balance O with H2O 4. balance H with H+ 5. equalize electrons transferred 6. add half-reactions and cancel 7. check elements and charges are balanced