Solutions

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 shaken.–The particles are made smaller.–The temperature is increased.

Why?

As size , rate

As To , rate

3. Agitation

Factors Affecting the Rate of Dissolution

1. temperature

2. particle size

4. nature of solvent or solute

More mixing, rate

∆ Surface Area

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

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

Solution Definitionssoluti

on:

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

gas

liquid

gas

gas

air (nitrogen, oxygen, argon gases)

humid air (water vapor in air)

Liquid Solutions

gas

liquid

solid

liquid

liquid

liquid

carbonated drinks (CO2 in water)

vinegar (CH3COOH in water)

salt water (NaCl in water)

Solid Solutions

liquid

solid

solid

solid

dental amalgam (Hg in Ag)

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

Solid Brass

An alloy is a homogeneous mixture of metals.

• Brass = Copper + Zinc• Solid brass

• homogeneous mixture

Copper

Zinc

Brass Plated

• Brass = Copper + Zinc• Brass plated

• heterogeneous mixture• Only brass on outside

Copper

Zinc

Hardened Steel

Iron

Carbon

Steel

Gold

24 karat gold 18 karat gold 14 karat gold

Gold

Copper

Silver

18/24 atoms Au24/24 atoms Au 14/24 atoms Au

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

Water

HOT

Solubility

A B

Before

Water

COLD

Add 1 drop of red food coloring

Miscible – “mixable”

two gases or two liquids that mix evenly

Experiment 1:

Water

HOT

AFTER

Water

COLD

A B

Solubility

Water Water

Oil

T30 sec

AFTER

Before

Add oil to water and shake

Immiscible – “does not mix”

two liquids or two gases that DO NOT MIX

Experiment 2:

T0 sec

Centrifugation

• Spin sample very rapidly: denser materials go to bottom (outside)

• Separate blood into serum and plasma– Serum (clear)– Plasma (contains red blood

cells ‘RBCs’)• Check for anemia (lack of iron)

Blood

RBC’s

Serum

A

AFTER

Before

B C

Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

Blood(a suspension) Centrifuge

Blood plasma(a solution)

White blood cellsRed blood cells

Making solutions

• In order to dissolve - the solvent molecules must come in contact with the solute.

• Stirring moves fresh solvent next to the solute.

• The solvent touches the surface of the solute.

• Smaller pieces increase the amount of surface of the solute.

O2-

H+

H+H2O

++

Water Molecule

Water is a POLAR molecule

Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

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?

O

H

H

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.

OH

H

H

NH

H

Electronegativeatoms

Hydrogen bond

Interstitial Spaces

Water Water Water Water Water Water WaterWaterdissolveddissolved

solidsolid

Oil Oil Oil Oil Oil Oil Oil

red foodred foodcoloringcoloring

Layer

Non-polar

Polar

"immiscible"

Water Water Water Water Water Water WaterWater

Dissolving of solid NaCl

Polar water molecules interact with positive and negative ions

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 468

Animation

Na+

Na+

Na+Cl-

Cl-Cl-

NaCl solid

salt

NaCl (aq) = Na+ = Cl-

Dissolving of solid NaCl

Animation by Raymond Chang All rights reserved.

SolvationSolvation

Solvation – Solvation – the process of dissolving

solute particles are separated and pulled into solution

solute particles are surrounded by solvent particles

Dissolving of NaCl

Timberlake, Chemistry 7th Edition, page 287

HH

O

Na+

+

-- + -+

+

-

Cl-

+ -

+

hydrated ions

Dissolving of Salt in Water

NaCl(s) + H2O Na+(aq) + Cl-(aq)

Cl-

ions

Na+

ions Water molecules

Dissolving of Salt in Water

NaCl(s) + H2O Na+(aq) + Cl-(aq)

Cl-

ions

Na+

ions Water molecules

Particle Model of a Solution

After mixing Saltwater solution

Water molecule

Chloride ion, Cl-

Sodium ion, Na+

Before mixing Fresh water

Water molecule