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Molcules and Materials- First year uni > Colloids & Nanoparticles > Flashcards

Colloids & Nanoparticles Flashcards

1
Q

What is a colloid?

A

A colloid is a mixture of solute and solvent in which the solute particles are between 1-1000 nm, the particles do not settle to the bottom

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2
Q

When does a change of state occur?

A

When an attractive force dominates, particles come closer together or when a kinetic motion causes the particles to move further apart

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3
Q

What is a sol?

A

A type of colloid where solid particles are dispersed in a liquid

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4
Q

Define an aerosol.

A

A type of colloid in which solid or liquid particles are dispersed in a gas.

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5
Q

Define foam.

A

A type of colloid where gas particles are dispersed in liquid.

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6
Q

What is an emulsion?

A

A type of colloid where liquid particles are dispersed in a liquid.

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7
Q

What is a solution?

A

A solution is a homogenous of two or more substances,

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8
Q

What is a suspension?

A

A mixture containing large, dispersed solid particles that can settle out or be separated by filtration.

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9
Q

What is the tyndall effect?

A

when a light beam is shone through a liquid colloid and the relatively large particles scatter light.

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10
Q

Name the three types of mixtures possible

A

colloids, suspensions and solutions

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11
Q

why can the large surface area of particles be toxic?

A

increased surface area means more potential for binding to toxics acting as a vectors

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12
Q

How do you calculate surface area of a sphere?

A

4pie rsquared

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13
Q

How do you calculate surface area of a rod or tube?

A

2(pir2) + 2pirh

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14
Q

Name the two forces in colloids

A

Electrostatic stabilization and steric stabilization

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15
Q

What is electrostatic stabilization?

A

it stabilizes the colloids by having a lot of charges on the surface, same charges will repel

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16
Q

What is steric stabilization?

A

Something on the surface of the particles that prevents them getting too close, attraction force of Van der waals and electrostatic repulsion are balanced

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17
Q

What is the neutralization reaction?

A

Acid + base -> salt + water

18
Q

Describe the difference between a hard acid and a soft acid?

A

A hard acid is where all of the acid groups dissociate (all H+s come off) whereas a soft acid is where only part of it dissociates

19
Q

Name the 3 stages in where a colloid goes from a stable system to phase separation?

A

sedimentation, flocculation and coagulation

20
Q

what is a micelle?

A

particle of colloidal dimensions that exists in equilibrium with the molecules or ions in solution from which it is formed

21
Q

Describe the structure of a micelle

A

composed of amphillic macromolecules, made of hydrophilic and hydrophobic blocks.

22
Q

Whats the difference between biomass and biochar?

A 
Biomass = plant material we start with
Biochar = what is produced from the plant material
23
Q

Define wettability

A

The spread of water on a surface

24
Q

Describe the difference between superhydrophobic and superhydrophillic in terms of wettability?

A

Superhydrophobic means the water droplets won’t spread at all
Superhyrophillic means the water will spread across the surface evenly

25
Q

Why should various methods of particle size analysis be considered? (3)

A
  • material suppliers and employers use many different types of instruments
  • use a different technique, likely to get a different answer
  • important to understand how analysis methods differ to compare data
26
Q

What does stokes law calculate?

A

The velocity of sedimentation

27
Q

Name 3 methods used to calculate particle size

A
  • sieves
  • laser diffraction
  • dynamic light scattering
  • manual microscopy
  • automated microscopy
28
Q

Advantages of laser diffraction in calculating particle size? (3)

A
  • uses a low power beam (non intrusive)
  • fast typically 3 mins to measure
  • precise and wide range
29
Q

Disadvantages of laser diffraction in calculating particle size? (3)

A
  • expensive
  • volume measurement assumes spherical particles when they may be different shapes
  • must be different in refractive indices between particles and suspending medium
30
Q

What size do particle’s diameters in a colloid range between?

A

1-1000nm

31
Q

How does high temperatures alter the physical state of a substance (solid/liquid/gas/) ?

A

particles move faster by kinetic energy causing a transition from solid > liquid > gas

32
Q

How does low temperatures alter the physical state of a substance (solid/liquid/gas/) ?

A

particles move less and attractive forces bring them back together gas > liquid > solid

33
Q

Why do colloids often have a milky colour?

A

particles large enough to scatter light causing it to bend

34
Q

Describe the properties of a solution?

A

it is ALWAYS transparent and light can pass through with no scattering from solute particles. e.g. sugar and water

35
Q

Name the balanced two forces in any colloidal system

A

Attractive force of van der waals and Electrostatic repulsion

36
Q

Describe sedimentation

A

When particles are heavier and there is a gravity effect where they start to settle first and as the concentration increases they start to agglomerate

37
Q

Describe flocculation

A

The charge is suddenly neutralized and the particles come together very quickly and then this agglomerate will have a higher density and will therefore settle out

38
Q

What does laser diffraction do?

A

It converts scattered light to particle size distribution

39
Q

How does laser diffraction measure particle size?

A

> particles pass through a laser beam and the light scattered by them is collected over a range of angles
the angle of diffraction is inversely related to particle size

40
Q

What does dynamic light scattering measure?

A

Diffusion constant and therefore you msut use stokes Einstein law to calculate particle size

41
Q

Name 3 features of a colloid

A
  • particle size must be in the range of 1 - 1000nm
  • mixture composed of particles in a dispersing medium
  • tyndall effect, shining a beam through the colloid causes the larger particles to scatter light which makes the substance appear cloudy

Molcules and Materials- First year uni (13 decks)

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