SOLUTION AND COLLOID

SPECIFIC LEARNING OBJECTIVE

At the end of the session the student should be able to explain: -Definitions of Solution and Colloids-System of Solutions and Colloids-Type of Solutions and Colloids

SOLUTIONConcentration

Types of solution

INTRODUCTION

Solution properties

Dialysis

No.1

No.2

No.3

No.4

No.5

SOLUTION

Definition

MATTER

INTRODUCTION

Classification

Mixture

Pure substance

No. 1

State of matter

THE STATE OF MATTER

Matter

Solid Liquid Gas

CLASSIFICATION OF MATTER

Matter

Mixture Pure substance

Homogeneous mixture

Heterogeneous mixture Element Compound

HOMOGENEOUS MIXTURE

Homogenous mixtures called solutions

And

Their distant relatives, colloidal suspensions

Solutions

• Solutions are homogeneous mixtures of two or more substances in which the components are present as atoms, molecules, or ions

• These uniformly distributed particles are too small to reflect light, and as a result solutions are transparent (clear) – light passes through them

SUBSTANCES OF SOLUTIONS

Solutions

Solute Solvent

•The substance is dissolved in a solvent is called solute

•The most abundant substance in a solution is called solvent

SOLUTE

Solute

Electrolyte

A solute that when dissolved in water forms a solution that conducts electricity.

Nonelectrolyte

A solute that when dissolved in water forms a solution that does not conduct electricity.

HEATS OF SOLUTION

Heat is usually absorbed or released when asolute dissolves in a solvent.1. The process is endothermic, if heat is

absorbed, and solution becomes cooler.2. The process is exothermic, if heat is

released, and solution temperature increases.

Endothermic : Solute + Solvent + Heat

Solution (NH4NO3 in water)

Exothermic : Solute + Solvent Solution + Heat (NaOH in water)

SOLUTIONConcentration

Types of solution

INTRODUCTION

Solution properties

Dialysis

No.1

No.2

No.3

No.4

No.5

SOLUTION

Types of solution

Medical termChemical term

No. 2

• Unsaturated• Saturated• Super saturated

• Hypotonic• Isotonic• Hypertonic

Classification of Solubility

• Three classify of solubility of a compound• 1. Soluble• 2. slightly soluble • 3. insoluble

SOLUBILITY

Chemical term

• Soluble substances dissolve completely in the solvent and form solution

• Insoluble substances do not dissolve in the solvent

• The term immiscible is used to describe a liquid solute that does not dissolve in a liquid solvent

Depend on the Polarity

Three type of polarity of a compound :1. Polar2. Semipolar3. Nonpolar

1. Soluble

SOLUBILITY

2. slightly soluble 3. insoluble

UNSATURATED, SATURATED AND

SUPERSATURATED SOLUTIONS

• Saturated solution, is a solution that contains the maximum amount of a solute in a given solvent, at a specific temperature.

• Unsaturated solution, is a solution that contains less solute that it has the capacity to dissolve.

• Supersaturated solution, contains more solute than is present in a saturated solution

SOLUBILITY

SUPERSATURATED SOLUTIONS

• Supersaturated solutions are usually prepared by forming a nearly saturated solution at a high temperature and then slowly cooling the solution to a lower temperature at which the solubility is lower. Such solutions are not stable. The addition of small amount of solid solute (or even a dust particle) will usually cause the excess solute to crystallize out of solution until the solution becomes saturated.

CRYSTALLIZATION CONVERTS A SUPERSATURATED SOLUTION TO A SATURATED SOLUTION

A supersaturated Seed crystal is added After excess solute is solution and induces rapid crystallized, the crystallization remaining solution is

saturated

SOLUTION

Types of solution

Medical termChemical term

No. 2

• Unsaturated• Saturated• Super saturated

• Hypotonic• Isotonic• Hypertonic

Hypotonic, Isotonic and Hypertonic solutions

• Hypotonic solutions : the solution with the lower concentration of solute

• If the concentration of water in the medium surrounding a cell is greater than that of the cytosol. Water enters the cell by osmosis

• Isotonic solutions : the solution being compared have equal concentration of solutes.

• When red blood cells are placed in a 0.9% salt solution, they neither gain nor lose water by osmosis

• Hypertonic solutions : The solution with the higher concentration of solutes.

• If red cells are placed in sea water (about 3% salt), they lose water by osmosis and the cells shrivel up.

Medical term

Red blood cells in the Hypotonic, Isotonic and Hypertonic solutions

Red blood cells with hypotonicsolution

Red blood cells with isotonicsolution

Red blood cells with hypertonicsolution

SOLUTIONConcentration

Types of solution

INTRODUCTION

Solution properties

Dialysis

No.1

No.2

No.3

No.4

No.5

SOLUTION

ConcentrationNo. 3

• Molarity (M) • Percent (%)

• Percent : a solution concentration that expresses the amount of solute in 100 parts of solution.

•Molarity (M) : a solution concentration that is expressed in term of the number of moles of solute contained in a liter of solution.

continued to next slide

SOLUTION

ConcentrationNo. 3

• Molality (m) • Normality (N)

• Normality (N) : a solution concentration that is expresses in term of the number of gram equivalent of solute contained in a liter of solvent.

•Molality (m) : a solution concentration that is expressed in term of the number of moles of solute contained in a kilogram of solvent.

continued to next slide

Continuation :

• Weight/weight percent : a concentration that expresses the mass of solute contained in 100 mass units of solution.

• Weight/volume percent : a concentration that expresses the grams of solute contained in 100 ml of solution.

• Volume/volume percent : a concentration that expresses the volume of liquid solute contained in 100 volume of solution.

DILUTION

The volumetric scales of concentration are those, like molar concentration and normality, in which the concentration is expressed on avolumetric scale, the amount of solute per fixed volume of solution, when theconcentration is expressed on a volumetricscale, the amount of solute contained in agiven volume of solution is equal to the product of the volume and the concentration:

Amount of solute = volume x concentration

continued

continued

If a solution is diluted, the volume is increased

and the concentration is decreased, but the

total amount of solute is constant. Hence, two

solutions of different concentrations but

containing the same amounts of solute will be

related to each other as follows:

Volume1 x concentration1 = Volume2 x concentration2

If any three terms in the above equation areknown, the fourth can be calculated. The quantities on both sides of the equation mustbe expressed in the same units

continued

SOLUTIONConcentration

Types of solution

INTRODUCTION

Solution properties

Dialysis

No.1

No.2

No.3

No.4

No.5

SOLUTION

Colligative properties (continued to next slide)

No. 4 SOLUTION PROPERTIES

Electrical conductivity and colligative properties

COLLIGATIVE PROPERTIES

• The properties that depend only on the concentration of solute particles present and not on the actual identity of the solute.

• Three closely related colligative properties are

1. Vapor pressure 2. Boiling point 3. Freezing point 4. Osmotic pressure

The equation for calculated the boiling point or freezing point difference between pure solvent

and solution

• Δ tb = nKbm• Δ tf = nKfm

Δ t is the boiling point or freezing point difference between pure solvent and solution.

Kb and Kf are constants characteristic of the solvent used in the solution.

for example : Calculate the boiling and freezing points of the following solutions

• 171.0 g of sugar (C12H22O11) is dissolved in 1.00 kg of

water, Kb = 0.52 0C/m and Kf = 1.86 0C/m

• Answer :

a. To fine the boiling point, calculate solution

molality :

171.0 g (C12H22O11) 1 mol C12H22O11 =

342.0 g C12H22O11

= 0.50 mol C12H22O11

m = moles of solute/1 kg of solvent = 0.50 mol/1.0 kg

= 0.50 mol/kg continued to next slide

x

Continuation:

b. Determine n : because sugar does not dissociate upon dissolving, n = 1.

c. Δ tb = nKbm = (1)(0.52 0C/m)(0.50m) = 0,26 0C

d. Δ tf = nKfm = (1)(1.86 0C/m)(0.50m) = 0,93 0C

OSMOTIC PRESSURE

• Is the hydrostatic pressure required to prevent the net flow of solvent through a semipermeable membrane into a solution.

• Osmotic pressure ()

= nMRT (van’t Hoff equation)

T = temperature in Kelvins R = the ideal gas constant (0.82 L-atmosphere/degree.mole) M = the solution molarity

OSMOSIS

• The process in which solvent flows through a semipermeable membrane into a solution.

SOLUTIONConcentration

Types of solution

INTRODUCTION

Solution properties

Dialysis

No.1

No.2

No.3

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No.5

SOLUTION

DialysisNo. 5

• Earlier we discussed semipermeable membranes that selectively allow solvent to pass but retain dissolved solutes during osmosis.

• Dialysis, another membrane process, is also important in living organisms.

Continuation

• Dialyzing membranes :

• A semipermeable membranes with pores large enough to allow solvent molecules, other small molecules, and hydrat ions to pass through (are semipermeable membranes with larger pores than osmotic membranes).

Continuation

• Dialysis : A process in which solvent molecules, other small molecules, and hydrat ions pass from a solution through a membrane (is the passage of ions and small molecules through such membranes).

DIALYSIS.This is one method of dialysis used to purify proteins

Application of Dialysis

Scheme of dialysis process

Dialysis tubing

Dialysate + waste product

Fresh dialysate

A similar technique is used to clean the blood of people suffering kidney

mal function

• The blood is pumped through tubing made of a dialyzing membrane.

• The tubing passes through a bath in which impurities collect after passing out of the blood.

• Blood proteins and other important large molecules remain in the blood.

HEMODIALYSIS

Scheme of hemodialysis process

dialysat

dialysat

blood

blood

Continuation

• Dialysis is most commonly used to remove salts and other small molecules from solutions of macromolecules. During the separation and purification of biomolecules, small molecules are added to selectively precipitate or dissolve the desire molecule.

Continuation

• Dialysis is also useful for removing small ions and molecules that are weakly bound to biomolecules. Protein cofactors such as NAD, FAD, and metal ions can be dissociated by dialysis. The removal of metal ions is facilitated by the addition of a chelating agent (EDTA) to the dialysate.

• Minerals are bound by EDTA, these are: Ca, Fe, etc.

EDTA : Ethylenediaminetetra-acetic acid

EDTA with Metal

Ca, Fe, etc

COLLOID

Types of colloid

Colloid properties

INTRODUCTIONNo.1

No.2

No.3

COLLOID

INTRODUCTION :° Definition° Diameter of colloid particle

No. 1

• colloids (or colloidal suspensions) are homogeneous mixture of two or more components in which there is more of one component than of the others.

Definition

• In solutions the terms solvent and solute are used for the components, but in colloids the terms dispersing medium (for solvent) and dispersed phase (for solute) are used.

DIAMETERS OF THE DISPERSED PHASE

• The dispersed phase of colloids is made up of much larger particles (very large molecules or small pieces of matter) with diameters:

10ˉ7 to 10 ˉ5 cm (10 – 1000 A˚)

COLLOID

Types of colloid

Colloid properties

INTRODUCTIONNo.1

No.2

No.3

COLLOID

Types of colloid

No.2

TYPES OF COLLOID

Type Name

Examples

Aerosol

FoamEmulsionSolSolid foam

Fog, aerosol sprays, some air pollutantsSmoke, some air pollutantsWhipped cream, shaving creamMilk, mayonnaisePaint, ink, gelatin dessertMarshmallow, pumice stone, foam rubberButter, cheesePearls, opals, colored glass, some metal alloys

Dispersing medium

Dispersed phase

Gas

GasLiquidLiquidLiquidSolid

SolidSolid

Liquid

SolidGasLiquidSolidGas

LiquidSolid

LYOPHOBIC AND LYOPHILIC SYSTEM

Colloidal solutions with a liquid as Dispersion medium can be dividedroughly into two Categories :1. Lyophilic Sols2. Lyophobic Sols

DIFFERENCES BETWEEN

THE TWO TYPES1. SURFACE TENSION

SIMILAR TO THAT OF DISPERSION MEDIUM.

2. VISCOSITY SIMILAR TO THAT OF MEDIUM.

3. SMALL QUANTITIES OF ELECTROLYTES CAUSE PRECIPITATION.

4. THE PARTICLES ARE EASILY DETECTED IN THE ULTRAMICROSCOPE.

5. THE PARTICLES MIGRATE IN ONE DIRECTION IN AN

ELECTRIC FIELD.

1. SURFACE TENSION OFTEN LOWER THAN THAT OF DISPERSION MEDIUM.

2. VISCOSITY MUCH HIGHER THAN THAT OF MEDIUM.

3. SMALL QUANTITIES OF ELECTROLYTES HAVE LITTLE EFFECT, BUT LARGE AMOUNTS MAY CAUSE SALTING OUT.

4. THE PARTICLES CANNOT BE READILY DETECTED IN THE ULTRAMICROSCOPE.

5. THE PARTICLES MAY MIGRATE IN EITHER DIRECTION OR NOT AT ALL IN ELECTRICAL FIELD.

COLLOID

Types of colloid

Colloid properties

INTRODUCTIONNo.1

No.2

No.3

COLLOID

Colloid propertiesNo.3

TYNDALL EFFECTBROWNIAN MOVEMENT

COLLOID DESTRUCTION

COLLOID FORMATION

EMULSIFYING AGENTS OR STABILIZING AGENTS

TYNDALL EFFECT

• When a beam of light passes through them, they will be scattered the light, and the path of the light becomes visible.

• And hence it is generally called the Tyndall effect.

The light beam passes from left to right through a purple gold sol (a colloid), a blue copper sulfate solution, and colloidal iron (III) hydroxide. The light path can be seen in both colloids, but not in the copper sulfate solution.

source

colloid

CuSO4

Fe(OH)3

BROWNIAN MOVEMENT

• As is to be expected, because of their small size, colloidal particles are seen in the ultramicroscope to display vigorous Brownian movement.

COLLOID FORMATION AND DESTRUCTION

• Much of the interest in colloids is related to their formation or destruction.

• Colloid particles tend to attract and absorb ions that are present in the dispersing medium.

• The charge (+ or -) of the adsorbed ions depends on the nature of the colloid, but all colloid particles within a particular system will attract only one charge or the other.

• This repulsion help prevent the particles from coalescing into aggregates large enough to settle out.

• Emulsifying agents is substances that stabilize the colloids (prevented from coalescing)

• For examples : 1. Egg : the compound in the egg yolk acting as the emulsifying agents 2. Soaps and detergents 3. Etc (CMC = carboxyl methyl cellulose )

EMULSIFYING AGENTS OR STABILIZING AGENTS

Summary Reference:

• Mushtaq Ahmad, Essentials of Medical Biochemistry 6th Edition, Vol.1-2, Merit Publisher, Multan, 1999