chemistry 6 properties of matter

Imran Syakir Mohamad Chemistry DACS 1233 1

Properties Of Matter

Chapter 6


Three States of Matter


3 Phases

Solid phase - ice

Liquid phase - water

Phase Changes

Phase changes, trans-formations from one phase to another, occur when energy (usually in the form of heat) is added or removed.

Gas phase - steamH2O (l) H2O (g)

H2O (s) H2O (l)

H2O (s) H2O (g)

Imran Syakir Mohamad Chemistry DACS 1233 4E

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Phase Changes

Melting solid liquid

Freezing liquid solid

Vaporization liquid gas

Condensation gas liquid

Sublimation solid gas

Deposition gas solid


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

Phase Diagram of Water


• 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.

Physical Characteristics of Gases

Gases


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


Units of Pressure

1 pascal (Pa) = 1 N/m2

1 atm = 760 mmHg = 760 torr

1 atm = 101,325 Pa Barometer

Pressure = ForceArea


Sea level 1 atm

4 miles 0.5 atm

10 miles 0.2 atm


As P (h) increases V decreases


P 1/V

P x V = constant

P1 x V1 = P2 x V2

Boyle’s Law

Constant temperatureConstant amount of gas


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

V1 = 946 mL

P2 = ?

V2 = 154 mL

P2 = P1 x V1

V2

726 mmHg x 946 mL154 mL

= = 4460 mmHg


Chemistry in Action:

Scuba Diving and the Gas Laws

P V

Depth (ft)

Pressure (atm)

0 1

33 2

66 3


As T increases V increases

Charles’ & Gay-Lussac’s Law


Variation of gas volume with temperature at constant pressure.

V TV = constant x T

V1/T1 = V2/T2 T (K) = t (0C) + 273.15

Temperature must bein Kelvin


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 = 3.20 L

T1 = 398.15 K

V2 = 1.54 L

T2 = ?

T2 = V2 x T1

V1

1.54 L x 398.15 K3.20 L

= = 192 K

V1/T1 = V2/T2


Avogadro’s Law

V number of moles (n)

V = constant x n

V1/n1 = V2/n2

Constant temperatureConstant pressure


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 1 volume NO


Ideal Gas Equation

Charles’ law: V T(at constant n and P)

Avogadro’s law: V n(at constant P and T)

Boyle’s law: V (at constant n and T)1P

V nT

PV = constant x = R

nT

P

nT

P

R is the gas constant

PV = nRT


The conditions 0 0C and 1 atm are called standard temperature and pressure (STP).

PV = nRT

R = PVnT

=(1 atm)(22.4L)

(1 mol)(273.15 K)

R = 0.082057 L • atm / (mol • K)

Experiments show that at STP, 1 mole of an ideal gas occupies 22.4 L.


What is the volume (in liters) occupied by 49.8 g of HCl at STP?

PV = nRT

V = nRTP

T = 0 0C = 273.15 K

P = 1 atm

n = 49.8 g x 1 mol HCl36.45 g HCl

= 1.37 mol

V =1 atm

1.37 mol x 0.0821 x 273.15 KL•atmmol•K

V = 30.6 L


Molar Mass (M ) of a Gaseous Substance

dRTPM = d is the density of the gas in g/L

Density (d) Calculations

d = mV

d = PMRT

m is the mass of the gas in g

M is the molar mass of the gas

PV = nRT = RT mM

PM = RTmV

= dRT


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

g C6H12O6 mol C6H12O6 mol CO2 V CO2

5.60 g C6H12O6

1 mol C6H12O6

180 g C6H12O6

x6 mol CO2

1 mol C6H12O6

x = 0.187 mol CO2

V = nRT

P

0.187 mol x 0.0821 x 310.15 KL•atmmol•K

1.00 atm= = 4.76 L


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

Liquids


Cohesion is the intermolecular attraction between like moleculesAdhesion is an attraction between unlike molecules

Adhesion

Cohesion

When adhesion is greater than cohesion, the liquid rises in the capillary tube.

When cohesion is

greater than adhesion, a

depression of the liquid in the capillary

tube. water mercury


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

Strong intermolecular forces

High viscosity


• 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.

Unit Cell

latticepoint

Unit cells in 3 dimensions

Solids


Shared by 8 unit cells

Shared by 2 unit cells


1 atom/unit cell(8 x 1/8 = 1)

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

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


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

d = mV

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

4 atoms/unit cell in a face-centered cubic cell

m = 4 Ag atoms107.9 gmole Ag

x1 mole Ag

6.022 x 1023 atomsx = 7.17 x 10-22 g

d = mV

7.17 x 10-22 g6.83 x 10-23 cm3

= = 10.5 g/cm3


Extra distance = BC + CD = 2d sin = n (Bragg Equation)


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?

n = 2d sin

n = 1 = 14.170 = 0.154 nm = 154 pm

d =n

2sin=

1 x 154 pm

2 x sin14.17

= 314.5 pm


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 ZnS CaF2


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

diamond graphite

carbonatoms


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


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 e-

mobile “sea”of e-


Types of Crystals

chemistry 6 properties of matter

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