Chemistry 6 Properties Of Matter

Properties Of Matter Chapter 6

Imran Syakir Mohamad

Chemistry DACS 1233

1

Three States of Matter

Imran Syakir Mohamad

Chemistry DACS 1233

2

Phase Changes Phase changes, trans-formations from one phase to another, occur when energy (usually in the form of heat) is added or removed. 3 Phases Gas phase - steam Liquid phase - water Solid phase - ice

Imran Syakir Mohamad

Chemistry DACS 1233

H2O (l)

H2O (g)

H2O (s)

H2O (l)

H2O (s)

H2O (g)

3

liquid  gas

Condensation gas  liquid Sublimation

solid  gas

Deposition

gas  solid

Imran Syakir Mohamad

Chemistry DACS 1233

Deposition

Vaporization

Condensation

liquid  solid

Freezing

Freezing

Evaporation

solid  liquid

Melting

Melting

Sublimation

Phase Changes

4

Imran Syakir Mohamad

Chemistry DACS 1233

5

Phase Diagram of Water

A phase diagram summarizes the conditions at which a substance exists as a solid, liquid, or gas.

Imran Syakir Mohamad

Chemistry DACS 1233

6

Gases Physical Characteristics of Gases •

Gases assume the volume and shape of their containers.

•

Gases are the most compressible state of matter.

•

Gases will mix evenly and completely when confined to the same container.

•

Gases have much lower densities than liquids and solids.

Imran Syakir Mohamad

Chemistry DACS 1233

7

Elements that exist as gases at 25 0C and 1 atmosphere

Imran Syakir Mohamad

Chemistry DACS 1233

8

Imran Syakir Mohamad

Chemistry DACS 1233

9

Force Pressure = Area

Units of Pressure 1 pascal (Pa) = 1 N/m2 1 atm = 760 mmHg = 760 torr Barometer

1 atm = 101,325 Pa Imran Syakir Mohamad

Chemistry DACS 1233

10

10 mi les

4 mil es Sea l evel

Imran Syakir Mohamad

Chemistry DACS 1233

0. 2 atm

0. 5 atm 1 atm

11

As P (h) increases Imran Syakir Mohamad

Chemistry DACS 1233

V decreases 12

Boyle’s Law

P α 1/V Constant temperature Constant amount of gas

P x V = constant P1 x V1 = P2 x V2 Imran Syakir Mohamad

Chemistry DACS 1233

13

A sample of chlorine gas occupies a volume of 946 mL at a pressure of 726 mmHg. What is the pressure of the gas (in mmHg) if the volume is reduced at constant temperature to 154 mL?

P1 x V1 = P2 x V2 P1 = 726 mmHg

P2 = ?

V1 = 946 mL

V2 = 154 mL

P1 x V1 726 mmHg x 946 mL P2 = = = 4460 mmHg 154 mL V2

Imran Syakir Mohamad

Chemistry DACS 1233

14

Chemistry in Action: Scuba Diving and the Gas Laws

P

Imran Syakir Mohamad

Chemistry DACS 1233

Depth (ft) 0

Pressure (atm) 1

33

2

66

3

V

15

Charles’ & Gay-Lussac’s Law

As T increases Imran Syakir Mohamad

Chemistry DACS 1233

V increases 16

Variation of gas volume with temperature at constant pressure.

VαT V = constant x T V1/T1 = V2/T2 Imran Syakir Mohamad

Temperature must be in Kelvin T (K) = t (0C) + 273.15 Chemistry DACS 1233

17

A sample of carbon monoxide gas occupies 3.20 L at 125 0C. At what temperature will the gas occupy a volume of 1.54 L if the pressure remains constant? V1/T1 = V2/T2 V1 = 3.20 L

V2 = 1.54 L

T1 = 398.15 K

T2 = ?

V2 x T1 T2 = = V1 Imran Syakir Mohamad

1.54 L x 398.15 K 3.20 L Chemistry DACS 1233

= 192 K

18

Avogadro’s Law V α number of moles (n) V = constant x n V1/n1 = V2/n2

Imran Syakir Mohamad

Chemistry DACS 1233

Constant temperature Constant pressure

19

Ammonia burns in oxygen to form nitric oxide (NO) and water vapor. How many volumes of NO are obtained from one volume of ammonia at the same temperature and pressure? 4NH3 + 5O2

4NO + 6H2O

1 mole NH3

1 mole NO

At constant T and P 1 volume NH3

Imran Syakir Mohamad

1 volume NO

Chemistry DACS 1233

20

Ideal Gas Equation Boyle’s law: V α 1 (at constant n and T) P Charles’ law: V α T (at constant n and P) Avogadro’s law: V α n (at constant P and T) nT Vα P

nT nT V = constant x =R P P R is the gas constant PV = nRT

Imran Syakir Mohamad

Chemistry DACS 1233

21

The conditions 0 0C and 1 atm are called standard temperature and pressure (STP). Experiments show that at STP, 1 mole of an ideal gas occupies 22.4 L.

PV = nRT PV R= nT (1 atm)(22.4L) = (1 mol)(273.15 K) R = 0.082057 L • atm / (mol • K) Imran Syakir Mohamad

Chemistry DACS 1233

22

What is the volume (in liters) occupied by 49.8 g of HCl at STP? T = 0 0C = 273.15 K

PV = nRT nRT V= P

P = 1 atm n = 49.8 g x

1.37 mol x 0.0821 V=

L•atm mol•K

1 mol HCl = 1.37 mol 36.45 g HCl

x 273.15 K

1 atm

V = 30.6 L Imran Syakir Mohamad

Chemistry DACS 1233

23

Density (d) Calculations PV = nRT = m RT M

PM = m RT = dRT V d=

PM

RT

d=

m V

m is the mass of the gas in g

M is the molar mass of the gas

Molar Mass (M ) of a Gaseous Substance M=

dRT P

Imran Syakir Mohamad

d is the density of the gas in g/L Chemistry DACS 1233

24

Gas Stoichiometry What is the volume of CO2 produced at 370 C and 1.00 atm when 5.60 g of glucose are used up in the reaction: C6H12O6 (s) + 6O2 (g) g C6H12O6 5.60 g C6H12O6 x

V=

nRT = P

Imran Syakir Mohamad

mol C6H12O6

6CO2 (g) + 6H2O (l) mol CO2

V CO2

6 mol CO2 1 mol C6H12O6 x = 0.187 mol CO2 180 g C6H12O6 1 mol C6H12O6 L•atm x 310.15 K mol•K = 4.76 L 1.00 atm

0.187 mol x 0.0821

Chemistry DACS 1233

25

Liquids Properties of Liquids Surface tension is the amount of energy required to stretch or increase the surface of a liquid by a unit area.

Strong intermolecular forces High surface tension

Imran Syakir Mohamad

Chemistry DACS 1233

26

Cohesion is the intermolecular attraction between like molecules Adhesion is an attraction between unlike molecules Adhesion When adhesion is greater than cohesion, the liquid rises in the capillary tube. Imran Syakir Mohamad

Cohesion

water

mercury Chemistry DACS 1233

When cohesion is greater than adhesion, a depression of the liquid in the capillary tube. 27

Viscosity is a measure of a fluid’s resistance to flow.

Strong intermolecular forces High viscosity

Imran Syakir Mohamad

Chemistry DACS 1233

28

Solids • A crystalline solid possesses rigid and long-range order. In a crystalline solid, atoms, molecules or ions occupy specific (predictable) positions. • An amorphous solid does not possess a well-defined arrangement and long-range molecular order. A unit cell is the basic repeating structural unit of a crystalline solid. lattice point

Unit Cell Imran Syakir Mohamad

Unit cells in 3 dimensions Chemistry DACS 1233

29

Imran Syakir Mohamad

Chemistry DACS 1233

30

Imran Syakir Mohamad

Chemistry DACS 1233

31

Imran Syakir Mohamad

Chemistry DACS 1233

32

Imran Syakir Mohamad

Chemistry DACS 1233

33

Shared by 2 unit cells

Shared by 8 unit cells Imran Syakir Mohamad

Chemistry DACS 1233

34

1 atom/unit cell (8 x 1/8 = 1) Imran Syakir Mohamad

2 atoms/unit cell (8 x 1/8 + 1 = 2) Chemistry DACS 1233

4 atoms/unit cell (8 x 1/8 + 6 x 1/2 = 4) 35

Imran Syakir Mohamad

Chemistry DACS 1233

36

When silver crystallizes, it forms face-centered cubic cells. The unit cell edge length is 409 pm. Calculate the density of silver. m d= V

V = a3 = (409 pm)3 = 6.83 x 10-23 cm3

4 atoms/unit cell in a face-centered cubic cell 1 mole Ag 107.9 g -22 x m = 4 Ag atoms x = 7.17 x 10 g 23 mole Ag 6.022 x 10 atoms 7.17 x 10-22 g m 3 = = 10.5 g/cm d= V 6.83 x 10-23 cm3

Imran Syakir Mohamad

Chemistry DACS 1233

37

Imran Syakir Mohamad

Chemistry DACS 1233

38

Extra distance = BC + CD = 2d sinθ = nλ (Bragg Equation) Imran Syakir Mohamad

Chemistry DACS 1233

39

X rays of wavelength 0.154 nm are diffracted from a crystal at an angle of 14.170. Assuming that n = 1, what is the distance (in pm) between layers in the crystal? nλ = 2d sin θ θ = 14.170 λ = 0.154 nm = 154 pm

n=1 nλ

1 x 154 pm = d= 2 x sin14.17 2sinθ = 314.5 pm Imran Syakir Mohamad

Chemistry DACS 1233

40

Types of Crystals Ionic Crystals • Lattice points occupied by cations and anions • Held together by electrostatic attraction • Hard, brittle, high melting point • Poor conductor of heat and electricity

CsCl Imran Syakir Mohamad

ZnS Chemistry DACS 1233

CaF2 41

Types of Crystals Covalent Crystals • Lattice points occupied by atoms • Held together by covalent bonds • Hard, high melting point • Poor conductor of heat and electricity carbon atoms

diamond

Imran Syakir Mohamad

Chemistry DACS 1233

graphite

42

Types of Crystals Molecular Crystals • Lattice points occupied by molecules • Held together by intermolecular forces • Soft, low melting point • Poor conductor of heat and electricity

Imran Syakir Mohamad

Chemistry DACS 1233

43

Types of Crystals Metallic Crystals • Lattice points occupied by metal atoms • Held together by metallic bonds • Soft to hard, low to high melting point • Good conductors of heat and electricity Cross Section of a Metallic Crystal nucleus & inner shell emobile “sea” of e-

Imran Syakir Mohamad

Chemistry DACS 1233

44

Types of Crystals

Imran Syakir Mohamad

Chemistry DACS 1233

45