Exam 2 Flashcards
Which of the following has a surface excess more than the bulk? What happens to the surface tension for the solution?
A) NaCl; surface tension decreases
B) KOH; Surface tension increases
C) CH3(CH2)11OSO3Na ; increases
D) CH3(CH2)11(OCH2CH2)nOH ; decreases
D) surfactant, decreases
What is the name of the condition when competitive growth will precipitate out larger particles drawing material from smaller particles due to minimization of surface energy?
Ostwald Ripening
What is the temperature where a non-ionic surfactant’s solubility decreases and turbidity is observed?
Cloud Point Temperature
Which of the following will cause surface tension to decrease?
a) Lowering the temperature
b) Addition of surfactant
c) Addition of salt like NaCl
d) Increasing the temperature
e) A and B only
f) A and C only
g) C and D only
h) B and D only
i) B, C, and D only
h
If a quantum confined nanoparticle’s radius increases, what type of photon is necessary to promote an optical excitation equal to its bandgap energy compared to the original nanoparticle? (Energy and Wavelength)
Lower energy, longer wavelength photon
Which of the following properties for a single composition nanoparticle will increase compared to a bulk particle (one at macro size)?
a) Surface Energy
b) Melting Point temperature
c) Bandgap
d) All of the above
e) A and C only
e
What happens to surface tension at a concentration greater than the CMC for a pure, single component surfactant?
Stays the same
What term refers to the act of two particles coming together and not increasing the overall SA appreciably?
Aggregation
Which techniques are used to determine the size of typical Quantum Dot materials
TEM, Absorption Spectroscopy, Line broadening using X-ray diffraction
Actual particles can deviate from the Stokes model for sedimentation if they are:
Asymmetrical, solvated
Uses for surfactants
Stabilization of thin films
Formation of emulsions
Lubrication