Dispersion of Matter

Department of Nutrition Science

Purdue University

Purdue griffin

Definitions

Comparative Characteristics of Dispersions

Group Assignments

Calculations and Tables

Grading Sheet

 

The forms and tables included in these pages are for the purpose of illustrating how you should prepare tables in your notebook before coming to lab. They are not for the purpose of direct entry of data during the lab. Please use them in the way intended. The grade sheets indicate the materials that should be included in the formal write and the point value assigned to each element.

Download your dispersion of matter handout here!!

 

Dispersion of Matter

Food dispersion - a system consisting of one or more dispersed or discontinuous phases in a continuous phase.

Solution - a one-phase system where all particles are the size of atoms, molecules, or small ions (size < 1 nm).

Colloid - two or more phases in which the dispersed phase consists of particles ranging in size from 1-100 nm (10-1000 Å).

Suspension - two or more phases in which the particle size of the dispersed phase is greater than that of colloidal particles.

 

Dispersions can also be classified according to the physical state.

sol - dispersion of solids in liquid.

emulsion - dispersion of liquid in liquid (where liquids are immiscible).

foam - dispersion of gas in liquid.

 

surfactant - gathers at the interface and lowers interfacial tension. Decreases the tendency for two phases to separate.

 

Experiment 1-Solutions

There are three dispersion types, based on molecular size of particles: Solutions (small), Colloidal Dispersion (large), and Suspensions (visible chunks).

A solution consists of: solvent (ex. pure water) and solute (dissolved stuff).  

Note: Colligative property - a property such as boiling point elevation, freezing point depression, vapor pressure lowering, or osmotic pressure elevation. These properties depend on the number of particles of solute but NOT on their chemical identities.

Experiment 2-Emulsions

Dispersions can be classified based on particle state (solid, liquid, gas).  You can see this with the table below:

Solid

Liquid

Gas

Solid

-

Sol

Aerosol

Liquid

-

Emulsion

-

Gas

Solid foam

Foam

-

If you suspend a solid into a liquid, you have a sol.  If you suspend a gas into liquid, you have foam.  If you suspend a liquid into liquid, you have an emulsion.

Emulsion - two immiscible (unblendable) liquid phases, one dispersed in the other as tiny droplets (0.1 to 50 m m in diameter)

 

discontinuous (dispersed) phase- droplet phase

continuous phase - matrix in which droplets are dispersed

The discontinuous phase is poured into the continuous phase.

Ex. Water (discontinuous) poured into oil (continuous)

      Oil (discontinuous) poured into water (continuous)

 

You can add sudan red dye to oil to see where the oil is when poured into or mixed with water.

Without sudan red dye:

                   

Water in oil (w/o) Oil in water (o/w)

without sudan red dye

With sudan red dye added to oil:

w/o o/w

with sudan red dye

Add emulsifiers to decrease surface tension at the interface of the two liquids. Emulsifiers have both hydrophobic and hydrophilic ends.

emulsifiers

There are two types of emulsions we will study:

Temporary                                                    Permanent

                                                                        Has added emulsifiers

emulsions

Oil will want to have the least surface area exposed to water

In order to keep oil from separating from water, we add emulsifiers (polar head + non-polar tail) to lower surface tension.

Emulsifiers are classified by their hydrophilic-lipophilic balance (HLB) number (Range is 0-20).  Greater than 7 means O/W emulsion.  Less than 7 means W/O emulsion.

For note: the continuous phase is not always in greater percentage (Ex. mayonnaise).

 **Use Sorvall Omni-mixer for Experiment 2.  USE PLASTIC BEAKERS.**

Bile can be found in larger freezer.  Ask me first if you aren't sure where it is.

Use a TINY amount of sudan red dye.

Experiment 3 - Foaming Properties of Proteins

(START THIS EXPERIMENT EARLY!!)

**USE BLENDER**

Foams

foam

Almost everything that makes volume increase makes stability decrease and vice versa.

Proteins are used to fix the air molecules into place in foams, fitting in between, and stabilizing the air molecules.

**USE GLASS GRADUATED CYLINDERS IN WATER BATH AND PLASTIC GRADUATED CYLINDERS AT ROOM TEMPERATURE**

        We will be looking for what effect heat has on foam volume.

You'll find albumin in the  freezer.  Ask me first if you aren't sure where it is.

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Comparative Characteristics of Dispersions

 

Characteristic

True solutions

Colloidal dispersions

Suspensions

Particle size

less than 1 millimicron in diameter (< 1 nm)

1 millimicron to 0.1 or 0.2 micrometers (m m) in diameter (1-100 nm)

greater than 0.2 (m m) in diameter

Nature of particles

ions or small molecules

macromolecules or small groups of molecules

large groups of molecules

Type of movement

constant kinetic motion

Brownian movement

gravitational movement

Type of charge on particles

uncharged or some positive and some negative

all positive or all negative

usually uncharged

Visibility of particles

invisible under any microscope

visible under electron microscope

visible under ordinary microscope

Filterability of particles

pass through most membranes and parchments

pass through usual filters but not most membranes

do not pass through filters

Stability

very stable

moderately stable

unstable

Gel formation

usually not capable of gel formation

capable of gel formation

not capable of gel formation

Number of phases

1

2 or more

2 or more

Transparency

transparent

transparent-translucent

usually opaque

Effect on colligative properties

great

little

almost none

Example

syrup

protein sol (milk)

applesauce

 

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Lab #3 Dispersion of Matter Groups

 

Experiment 1-Solutions

  All groups calibrate thermometers.

Group

Step

1

4, 5

2

3, 5

3, 5

2

4

6

 

Experiment 2-Emulsions

Group #1 Variation # 1,9,6,14

Group #2 Variation # 2,10,7,15

Group #3 Variation # 3,11,8,16

Group #4 Variation # 4,12

Group #5 Variation # 5,13

 

Experiment 3-Foaming of Proteins

Do both room temperature and 40oC for assigned variation

Group #1 Variation # a,b

Group #2 Variation # c

Group #3 Variation # d

Group #4 Variation # e,f

Group #5 Variation # g,h

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Lab #3 Dispersion of Matter

 

Experiment 1-Solutions - Get these experiments going as soon as possible as it takes a long time to get to the ultimate temperatures, especially in the case of sucrose.

1. Calibrate thermometers (thermometers are in the storeroom) by boiling DI (deionized) water.

Example: If thermometer reads 99o C at boiling then subtract 1o C from the final temperatures you are supposed to be heating to. If the thermometer reads 102o C then add 2o C to the final temperatures.

2. Use reagent grade NaCl and sucrose ( as opposed to table salt or sugar).

3. Use pipettes to remove solutions at certain temperature points.

4. Example of Calculations:

Formula found in lab manual

MW sucrose = 342.3g/mol

MW NaCl = 58.44g/mol

 

Expected salt concentration for 101o C:

101o C - 100o C = 0.51o C/mol * X g NaCl/ml H2O * 1000/58.44g/mol* 2

1o C = 17.45o C * X g NaCl/ml H2O

0.06g NaCl/ml H2O = X

% Soluble Solids:

Using X from above ...

X/(X+1)] *100 = %

For 101o C : (0.06/1.06) *100 = 6%

5. Be sure to draw a graph for the observed vs. the calculated data for steps 2,3,4, and 6.

 

Step 2:

NaCl

Temperature (C)

Observed % soluble solids from refractometer

Expected
g NaCl/g water (see above)

Calculated % soluble solids (see above)

101

 

 

 

105

 

 

 

106

 

 

 

 

Steps 3 and 4:

Sucrose

Temperature (C)

% soluble solids from refractometer

Calculated

g sucrose/g water

Calculated % soluble solids

100.5

 

 

 

101.5

 

 

 

102

 

 

 

103

 

 

 

106.5

 

 

 

112

 

 

 

114

 

 

 

130

 

 

 

 

Step 6:

Freezing point calculated (C)

Freezing point observed (C)

10% sucrose

 

 

10% NaCl

 

 

 

Experiment 2-Emulsions

1. Bile (porcine bile extract, Sigma) is in the freezer.

2. Use a very small amount (a little on the end of a spatula) of Sudan red dye in the oil.

3. Be sure to observe at least one oil in water (o/w) and one water in oil (w/o)emulsion.

4. Fill in chart by marking if there is an emulsion or if it is separated

Material

O/W

W/O

Control

1.

9.

Lecithin

2.

10.

Egg Yolk

3.

11.

Detergent

4.

12.

Bile

5.

13.

Tween 40

6.

14.

F-160

7.

15.

F-10

8.

16.

 

Experiment 3 - Foaming Properties of Proteins DO THIS FIRST

1. Measure the foam volume NOT the total volume of the dispersion

2. Use blender, not Sorvall Omni-mixer (Sorvall mixers may have oil on them that will destabilize the foams)

3. Mix on speed blend (or one of the other speeds at the high end).

4. Sample calculations:

a. 0.5% caseinate = 0.5 g caseinate; then add water up to 100 mL

 

g. 0.5% soy albumen + 0.5% vegetable oil =

0.5 g soy albumen + 0.5 g vegetable oil; then add water up to 100 mL

 Room Temperature

Material

0 minutes

5 minutes

30 minutes

a. 0.5% caseinate

 

 

 

b. 0.5% whey

 

 

 

c. 0.5% egg albumin

 

 

 

d. 0.5% soy albumen

 

 

 

e. 0.5% soy albumen + 0.5% cornstarch

 

 

 

f. 0.5% soy albumen + 0.5% sugar

 

 

 

g. 0.5% soy albumen + 0.5% oil

 

 

 

h. 0.5% soy albumen + 0.5% salt

 

 

 

 

40º C (104º F)

Material

0 minutes

5 minutes

30 minutes

a. 0.5% caseinate

 

 

 

b. 0.5% whey

 

 

 

c. 0.5% egg albumin

 

 

 

d. 0.5% soy albumen

 

 

 

e. 0.5% soy albumen + 0.5% cornstarch

 

 

 

f. 0.5% soy albumen + 0.5% sugar

 

 

 

g. 0.5% soy albumen + 0.5% oil

 

 

 

h. 0.5% soy albumen + 0.5% salt

 

 

 

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For Alternative Lab Report ONLY!

Lab 3 - Dispersion of Matter

Grading Sheet (25 pts. total)

 

I. Title, name, date, lab conditions (1/2 point)

II. Purpose (1 point)

III. Experimental procedures (1/2 point)

IV. Results

Exp. 1 - tables (2 points)

Exp. 1 - figures (3 points)

Exp. 3 - table (2 point)

Exp. 3 - figures (3 points)

V. Discussion

Exp. 1 - questions 1-4 (2 points)

- discussion (2 points)

Exp. 3 - questions 1-2 (3 points)

- discussion (2 points)

Discuss sources of error for Exp. 1 and 3 (1 point)

Discuss at least 2 references, one of these references must be from a journal. (2 points)

VI. References (in correct form) (1 point)

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Web Author: James R. Daniel, Ph. D.

 

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