Basic Concepts in Chemistry Physical Properties. Physical Properties A characteristic of a substance...

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Basic Concepts in ChemistryPhysical Properties

Physical Properties

A characteristic of a substance that you can observe and measure without changing

the identity of the substance.

Number vs. Quantity

• Quantity - number + unit

UNITS MATTER!!

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Types of measurement

Quantitative- can be measured and assigned a particular value.use numbers to describe- melting point - viscosity is a measure of how easily a fluid flows.- 4 meters,- 100 0C

Qualitative- can be observed and described without detailed measurements.

- the colour of aluminum is grey.- Hydrogen sulfide has a characteristic odour of rotten eggs.- Greenish-yellow gas could be a warning that chlorine gas is present.- extra large- hot

Scientists prefer

QuantitativeQuantitative - easy to check

• Easy to agree upon, no personal bias

• The measuring instrument limits how good the measurement is.

Examples of Qualitative Physical Properties

Property Examples

Colour Colourless, red, black

Odour Sweet, pungent, mouldy

State Solid, liquid, or gas

Texture Rough, smooth, bumpy

Lustre Shiny, dull

malleability Soft, pliable, hard

Quantitative Physical Properties

Property DescriptionViscosity Resistance to flow

Melting point Temperature of melting

Boiling point Temperature of boiling

Solubility Ability to dissolve in another substance

Hardness Ability to scratch another material

Conductivity Ability to conduct electricity or heat

Density Ratio of mass to volume

States of Matter

Gas, Liquid, and Solid

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 441

Gas Liquid Solid

Some Properties of Solids, Liquids, and Gases

Property Solid Liquid Gas

Shape Has definite shape Takes the shape of Takes the shape the container of its container

Volume Has a definite volume Has a definite volume Fills the volume of the container

Arrangement of Fixed, very close Random, close Random, far apartParticles

Interactions between Very strong Strong Essentially noneparticles

• To evaporate, molecules must have sufficient energy to break Intermolecular (IM) forces. Change of state from a liquid to a gas.

• Molecules at the surface break away and become gas.

• Only those with enough Kinetic energy (KE) escape.• Breaking IM forces requires energy. The process of

evaporation is endothermicendothermic.• Evaporation is a cooling process.• It requires heat.

Evaporation

Change from gas to liquid

Achieves a dynamic equilibrium with vaporization in a closed system.

What is a closed system?

A closed system means matter can’t go in or out. (put a cork in it)

Condensation

Energy Changes Accompanying Phase Changes

Liquid

Melting Freezing

Deposition

CondensationVaporization

Sublimation

Brown, LeMay, Bursten, Chemistry 2000, page 405

Melting / Boiling Point

Boiling pointof water

Freezing pointof water

Absolutezero

Celsius

100Celsiusdegrees

-273oC

Melting Point - change of state from solid to liquidMelting point: the temperature at which a solid turns into a liquid.Boiling point: the temperature at which a liquid turns into a gas.Boiling point of water is 100 0C.

Definitions

• Solution - Solution - homogeneous mixture

Solvent Solvent - present in greater amount

Solute Solute - substance being dissolved

Solutions

• What the solute and the solvent are determines–whether a substance will dissolve. –how much will dissolve.

• A substance dissolves faster if it is stirred or –The particles are made smaller. shaken.–The temperature is increased.

Solution = Solute + Solvent

• Solute - gets dissolved

• Solvent - does the dissolving– Aqueous (water)

– Tincture (alcohol)

– Amalgam (mercury)

– Organic• Polar• Non-polar

Dental filling

Nightmare on White StreetChem Matters, December 1996

Solution Definitionssoluti

alloy:

solvent: the substance that dissolves the solute

water salt

a homogeneous mixture

-- evenly mixed at the particle level

-- e.g., salt water

a solid solution of metals

-- e.g., bronze = Cu + Sn; brass = Cu + Zn

“will dissolve in”

refers to two gases or two liquids that forma solution; more specific than “soluble”

-- e.g., food coloring and water

miscible:

soluble:

Types of Solutions

Solute Solvent Solution

Gaseous Solutions

liquid

air (nitrogen, oxygen, argon gases)

humid air (water vapor in air)

Liquid Solutions

liquid

carbonated drinks (CO2 in water)

vinegar (CH3COOH in water)

salt water (NaCl in water)

Solid Solutions

liquid

dental amalgam (Hg in Ag)

sterling silver (Cu in Ag)Charles H.Corwin, Introductory Chemistry 2005, page 369

As size , rate

As To , rate

3. mixing

Factors Affecting the Rate of Dissolution

1. temperature

2. particle size

4. nature of solvent or solute

More mixing, rate

Classes of Solutionsaqueous solution:

water = “the universal solvent”

solvent = water

amalgam: solvent = Hg

e.g., dental amalgam

tincture: solvent = alcohol

e.g., tincture of iodine (for cuts)

organic solution: solvent contains carbon

e.g., gasoline, benzene, toluene, hexane

Non-Solution Definitions

insoluble: “will NOT dissolve in”

e.g., sand and water

immiscible: refers to two gases or two liquids that will NOT form a solution

e.g., water and oil

suspension: appears uniform while being stirred, but settles over time

Solubility

AFTERBefore

Add 1 drop of red food coloring

Miscible – “mixable”

two gases or two liquids that mix evenly

Experiment 1:

Solubility

Water Water

T30 sec

Before

Add oil to water and shake

Immiscible – “does not mix”

two liquids or two gases that DO NOT MIX

Experiment 2:

T0 sec

Solubility vs. Temperature

Timberlake, Chemistry 7th Edition, page 297

NaNO 3

Na 3PO 4

Temperature (oC)

020 40 60 80 100

Pure water does not conduct an electric current

Source ofelectric power

Purewater

Ionic Solutions conduct a Current

Source ofelectric power

Free ionspresent in water

Electrolytes

(a) Nonelectrolyte (b) Weak electrolyte (c) Strong electrolyte

Electrolytes

Timberlake, Chemistry 7th Edition, page 290

ElectrolytesElectrolytes - solutions that carry an electric current

NaCl(aq) Na+ + Cl- HF(aq) H+ + F-

strong electrolyte weak electrolyte nonelectrolyte

Solubility and the Environment

Chemical Stewardship

• Be responsible in how you dispose of and use chemicals.

• Chemical pollution can travel far – and harm organisms.

Frog with three legs – it hasmutated from chemical exposure.

Early Warning Signs…

Contamination of water where frog lives causes mutations.

Canary dies in the mine from bad air (cyanide). This is clue for minersto leave the mine…alive.

Pfiesteria

Fish sores from infection by pfiesteria.

Pfiesteria organism

Solvents

Solvents at the hardware store

Density

• Density is an INTENSIVEINTENSIVE property of matter.

- does NOT depend on quantity of matter. - color, melting point, boiling point, odor, density

• Contrast with EXTENSIVEEXTENSIVE

- depends on quantity of matter.- mass, volume, heat content (calories)

Styrofoam Brick

?It appears that the brick is ~40x more dense than the Styrofoam.

VV= =DD

BrickBrickStyrofoamStyrofoam

Styrofoam Brick

Which liquid has the highest density?

Coussement, DeSchepper, et al. , Brain Strains Power Puzzles 2002, page 16

least dense 1 < 3 < 5 < 2 < 4 most dense

Cube Representations

1 m3 = 1 000 000 cm3

Volume and DensityRelationship Between Volume and Density for Identical Masses of Common Substances

Cube of substance Mass Volume Density Substance (face shown actual size) (g) (cm3) (g/cm3)

Lithium

Aluminum

10 19 0.53

10 10 1.0

10 3.7 2.7

10 0.58 11.4

Density

Vensity

D = MV

M = D x V

V = MD

Volume

Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 41

4 cm4 cm

2 cm2 cm

Volume

Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 41

V = length x width x height

V = 2 cm x 2 cm x 2 cmV = 8 cm3

Volume = length x width x height

Volume = 6 cm x 2 cm x 3 cm

Volume = 36 cm3

Volume =

Volume = 28 cm3

Density of Some Common Substances

Density of Some Common Substance

Substance Density (g / cm3)

Air 0.0013* Lithium 0.53 Ice 0.917 Water 1.00 Aluminum 2.70 Iron 7.86 Lead 11.4 Gold 19.3

Density of Some Common Substance

Substance Density (g / cm3)

Air 0.0013* Lithium 0.53 Ice 0.917 Water 1.00 Aluminum 2.70 Iron 7.86 Lead 11.4 Gold 19.3

*at 0oC and 1 atm pressure

Consider Equal Volumes

The more massive object(the gold cube) has the_________ density.

Equal volumes…

…but unequal masses

aluminum gold

GREATER

Density = Mass

Volume

Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 71

Consider Equal MassesEqual masses……but unequal volumes.

The object with the larger volume (aluminum cube) has the density.

aluminum

smaller

Christopherson Scales

Two ways of viewing density

Equal volumes…

…but unequal masses

The more massive object(the gold cube) has thegreater density.

aluminum gold

Equal masses……but unequal volumes.

aluminumThe object with the larger volume (aluminum cube) has the smaller density.

Water Molecule

Water is a POLAR molecule

Water molecules “stick” together to

create surface tension to support

light weight objects.

Water Molecule

• What is a polar molecule?

• How does the polarity of water effect this molecule?

Hydrogenbond

• Hydrogen bonds occur

between two polar molecules, or between different polar regions of one large macro-molecule.

• One “relatively” negative region is attracted to a second “relatively” positive region.

Electronegativeatoms

Hydrogen bond

Reviewing ConceptsReviewing ConceptsPhysical Properties

• List seven examples of physical properties.

• Describe three uses of physical properties.

• Name two processes that are used to separate mixtures.

• When you describe a liquid as thick, are you saying that it has a high or low viscosity?

Reviewing ConceptsReviewing ConceptsPhysical Properties

• Explain why sharpening a pencil is an example of a physical change.

• What allows a mixture to be separated by distillation?

Basic Concepts in Chemistry Physical Properties. Physical Properties A characteristic of a substance...

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