Candidato:
CPF:
Seleção para o Semestre 2015.1
Instruções e informações
Nesta prova escrita deverão ser observadas as seguintes regras e procedimentos:
• A prova está dividida em duas partes: a Parte I engloba questões totalmente no idioma português
relacionadas a assuntos de Ciência dos Materiais; a Parte II engloba questões que incluem o uso do
idioma inglês, parcial ou totalmente. Ambas as Partes I e II referem-se aos assuntos elencados no
Anexo I do Edital que rege a presente seleção de acesso ao Programa de Pós-graduação em Ciência
dos Materiais da Universidade Federal do Vale do São Francisco.
• Nas questões na Parte II, responda apenas às perguntas referentes ao texto sorteado antes do
inı́cio da prova. Respostas para questões de quaisquer dos outros dois textos (não sorteados) serão
desconsideradas para efeito de correção e pontuação.
• O discente deverá manter o celular desligado durante toda a duração desta avaliação. Não é permitido mantê-lo desligado, mesmo que seja no modo silencioso. Quem infringir esta regra poderá
zerar a nota da prova.
• Não é permitida a utilização de calculadora, sob pena de imputação da nota zero ao infrator desta
norma.
• As marcações de itens devem ser feitas utilizando caneta esferográfica (preta ou azul). Marcações a
lápis ou com caneta de cor distinta à mencionada neste item serão desconsideradas.
• As folhas da prova não deverão ser desgrampeadas em hipótese alguma, sob pena de imputação da
nota zero ao infrator desta norma.
Questões - PARTE I
1. Sobre a ligação iônica, assinale o item correto dentre as opções a seguir:
(a) É o resultado da atração coulombiana entre as espécies com cargas opostas.
(b) Não envolve transferência de elétrons de um átomo para outro.
(c) É o tipo de ligação quı́mica que existe na interação entre dois átomos de carbono em uma
molécula de etileno (C2 H4 ).
(d) É um tipo de ligação quı́mica que é direcional.
(e) Nenhuma das respostas anteriores.
2. Sobre polı́meros, assinale o item correto dentre as opções a seguir:
(a) Poucos exemplos desses materiais apresentam alta ductibilidade.
(b) São materiais que resistem a altas temperaturas.
(c) Em geral, não apresentam propriedades magnéticas.
(d) Em geral, não são quimicamente inertes.
(e) Nenhuma das respostas anteriores.
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3. Sobre materiais semicondutores, assinale o item correto dentre as opções a seguir:
(a) À temperatura ambiente, geralmente se comportam como isolantes elétricos.
(b) São metais que sofreram um processo chamado usinagem.
(c) Európio e argônio são dois exemplos de materiais semicondutores.
(d) Não têm grande aplicação tecnológica devido à sua alta condutividade a baixas temperaturas.
(e) Nenhuma das respostas anteriores.
4. Dadas as afirmativas abaixo
(I) A ligação predominante nos materiais cerâmicos é a covalente;
(II) Os prótons presentes em ligações metálicas são responsáveis pela condutividade elétrica em
metais;
(III) Os ossos são excelentes materiais magnéticos, devido à alta concentração de cálcio que neles
há;
assinale, a seguir, a opção correta:
(a) Somente I é correta.
(b) Somente I e II são corretas.
(c) Somente II e III são corretas.
(d) Todas as afirmativas estão corretas.
(e) Nenhuma das afirmativas é correta.
5. Sobre a ligação covalente, assinale o item correto dentre as opções a seguir:
(a) É uma ligação não direcional.
(b) É predominante em materiais metálicos.
(c) Está relacionada a números de coordenação substancialmente menores que o previsto pelas
considerações de razão dos raios da ligação iônica.
(d) Nenhuma das alternativas é correta.
(e) Duas das alternativas são corretas.
6. Sobre a ligação metálica, assinale o item correto dentre as opções a seguir:
(a) É uma ligação não direcional.
(b) Envolve o compartilhamento de elétrons.
(c) Os elétrons de valência envolvidos em tal tipo de ligação são considerados delocalizados.
(d) Nenhuma das alternativas é correta.
(e) Todas as alternativas são corretas.
7. É SEMPRE correto afirmar que:
(a) Nylon, polietileno e fibra de vidro são exemplos de polı́meros.
(b) Na ausência de um campo magnético externo, os estados em cada subcamada são idênticos.
(c) O sal de cozinha puro (NaCl) é classificado como um compósito.
(d) Todas as alternativas são corretas.
(e) Nenhuma das alternativas é sempre correta.
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8. É SEMPRE correto afirmar que:
(a) Ambientes corrosivos aumentam a resistência mecânica de materiais.
(b) O ouro é um melhor condutor térmico do que a fibra de coco.
(c) O sal de cozinha puro (NaCl) é classificado como um compósito.
(d) Todas as alternativas são corretas.
(e) Nenhuma das alternativas é sempre correta.
9. Sejam as seguintes afirmativas:
(I) O argônio é um exemplo de gás nobre.
(II) As moléculas da água são ligadas por meio de pontes de hidrogênio.
(III) A ligação de van der Waals não envolve transferência nem compartilhamento de elétrons.
Sobre as afirmativas imediatamente acima, o único item CORRETO, dentre os que seguem, é:
(a) Somente I e II.
(b) Somente I e III.
(c) Somente II e III.
(d) Todas as afirmativas são corretas.
(e) Todas as afirmativas são incorretas.
10. A energia potencial global entre dois ı́ons adjacentes, EN , pode ser representada pela relação
EN = −
A
B
+ n,
r
r
onde r é a separação entre ı́ons adjacentes. Além disso, A, B e n são constantes e dependem das
caracterı́sticas do sistema em particular. Nessas condições, assinale a alternativa correta, dentre as
opções a seguir:
1/(1−n)
A
(a) A separação mı́nima entre ı́ons, quando EN tem seu valor mı́nimo, é igual a nB−4
.
A 1/(1−n)
.
(b) A energia mı́nima para esse sistema é igual a nB
A 1/(1+n)
(c) A separação mı́nima entre ı́ons, quando EN tem seu valor mı́nimo, é igual a nB
.
A 4/(1−n)
(d) A energia mı́nima para esse sistema é igual a nB
.
(e) Nenhuma das respostas anteriores.
11. Para o valor 4 do número quântico principal (n), é correto afirmar sobre os valores possı́veis para o
número quântico azimutal (`) e o número quântico magnético (m` ):
(a) Para ` = 0, temos m` = 0.
(b) Para ` = 2, temos m` = −2, −1, 0, 1, 2.
(c) ` = 4 não é um valor fisicamente possı́vel.
(d) Todas as alternativas acima são corretas.
(e) Nenhuma das alternativas é correta.
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Questões - PARTE II
As questões 12 a 14, referentes ao texto 1, intitulado Twenty-five years of conducting polymers.
12. Para responder a esta questão, baseie-se no texto a seguir, na Tabela Periódica logo abaixo dele e
no rol de conhecimentos cobrados no Anexo I do Edital que rege a presente seleção de mestrado:
Infrared measurements of the film treated with a trace amount of halogen had already led Shirakawa
to believe that this might have caused a drastic change in the electronic states of polyacetylene. MacDiarmid and Heeger had previously found that adding bromine to (SN )x increased its conductivity
tenfold. The trio therefore decided to expose high quality films of trans-polyacetylene to bromine
vapour at room temperature and measure the resulting conductivity using a four-probe method. They
were amazed to find that the conductivity increased by 10 million times in a few minutes the change
was so rapid that it wrecked the electronics of the measuring instrument! Iodine and AsF 5 also
produced large increases. Today, the best samples of polyacetylene doped in this way can achieve a
conductivity similar to that of copper.
Figura 1: Fonte – Callister, W.J., Materials Science and Engineering, 7th ed., John Wiley & Sons, Inc.,
2007.
É correto afirmar que:
(a) Two of the mentioned scientists in the text above had already found that adding a certain
halogen to (SN )x improved its conductivity.
(b) Two of the mentioned scientists in the text above had already found that adding bromine to
(SN )x improved its conductivity.
(c) Infrared measurements helped Shirakawa to be convinced that presence of halogen could change
the electronic states of polyacetylene.
(d) All the options above are correct.
(e) None of the options above is correct.
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13. Para responder a esta questão, baseie-se exclusivamente no texto a seguir:
CHANCE CONVERSATIONS and experimental accidents, as well as informed insight, often play a
pivotal role in orchestrating the direction of scientific endeavour. The ChemComm paper in 1977, in
which a polymer chemist Hideki Shirakawa, an inorganic chemist Alan MacDiarmid, and a physicist
Alan Heeger presented their discovery of the simplest conducting polymer, polyacetylene (doped with
halogens), was the result of one of the most famous examples. The story is well known to many
but is worth telling again of how three scientists, from different disciplines and different continents,
came together and made the intellectual connections that led to such a major breakthrough. This work
reinforced the then emerging concept of organic materials behaving not as traditional insulators but
as metals or semiconductors. It has driven many advances in materials science, electronic theory and
technological applications. The discovery of conducting polyacetylene was recognised by the award of
the Chemistry Nobel Prize in 2000.
É correto afirmar que:
(a) Hideki Shirakawa, Alan MacDiarmid and Alan Heeger are from the same continent.
(b) Hideki Shirakawa, Alan MacDiarmid and Alan Heeger are, all of them, chemists.
(c) Hideki Shirakawa, Alan MacDiarmid and Alan Heeger showed that pure halogens can behave
itselves as excelent conducting materials.
(d) All the options above are correct.
(e) None of the options above is correct.
14. Para responder a esta questão, baseie-se no texto logo a seguir e no rol de conhecimentos cobrados
no Anexo I do Edital que rege a presente seleção de mestrado:
Polyacetylene could be converted from an insulator, to a semiconductor, to a full metal, depending
on the concentration of dopant. Heeger says, however, that it took “some courage to propose the
existence of a metalinsulator transition in an organic polymer”. Here arose, perhaps, one of the first
examples of the scientific cultural gap between chemists and physicists becoming apparent. They used
languages, both based on quantum mechanics but with a different historical development, to describe
the same phenomena. Chemists thought of conducting polyacetylene in terms of a conjugated system
of overlapping π orbitals which is oxidised by the halogen to give a radical cation, and a halogen anion
partner. Physicists, using the language of condensed matter theory, talked about hole creation as an
electron is removed from the top of the valence band of polyacetylene the process of p-doping (the
reverse is n-doping, the polymer can also be reduced by an alkali metal). Conduction can be described
in terms of the hole migrating along the chain in the guise of various complex electronic states, or
quasi-particles, such as polarons, bipolarons or solitons. Heeger recalls that he and MacDiarmid
were well aware of the emerging communication problems, and they made a point of meeting up on
Saturday mornings to learn each others language and discuss ideas. “They were one of those little
gems of scientific creativity Ill never forget”, says MacDiarmid.
É correto afirmar que:
(a) Concentration of dopant was an important factor for the kind of transition that polyacetylene
could undergo.
(b) There were some difficulties of communication between physicists and chemists because of the
different ways of explaining the same phenomena.
(c) At least one of the ways of understanding the different languages, respectively, of chemists and
physicists, was meeting each other for learning and discussing ideas.
(d) All the options above are correct.
(e) None of the options above is correct.
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As questões 15 a 17, referentes ao texto 2, intitulado Anomalies in a waterlike model confined between
plates.
15. Para responder a esta questão, baseie-se no texto a seguir e no rol de conhecimentos cobrados no
Anexo I do Edital que rege a presente seleção de mestrado:
Water has several peculiar thermodynamic and dynamic properties not observed in other liquids.
This is the case of the density at room pressure that has a maximum at 4◦ C while in most materials
the density increases monotonically with the decrease of the temperature. In addition, between 0.1
MPa and 190 MPa water also exhibits an anomalous increase of compressibility and, at atmospheric
pressure, an increase of isobaric heat capacity upon cooling. Besides the thermodynamic anomalies
water also exhibits an unusual behavior in its mobility. The diffusion coefficient for normal liquids
increases with the decrease of pressure, for water it has a maximum at 4◦ C for 1.5 atm.
É correto afirmar que:
(a) Water behaves like the most of known liquids for any temperature and pressure.
(b) Water’s density at room temperature at 100◦ C is bigger than at 4◦ C.
(c) Under pressure below 0.1 MPa or above 190 MPa, water exhibits an anomalous increase of
compressibility.
(d) At atmospheric pressure, when water is cooled, the isobaric heat capacity becomes bigger.
(e) None of the options above is correct.
16. Para responder a esta questão, baseie-se exclusivamente no texto a seguir:
In this paper, the effects of confining a system of particles interacting through core-softened is explored. The formation of three layers, two close to the walls and one central, is observed for large
values of d*, while two layers are observed for small values of d*. In addition the region in the
pressure-temperature phase diagram where the density anomaly appears moves to lower temperatures. These results are similar to the results obtained in atomistic and coarse-grained models where
unlike our model the directionality of the h-bonds is explicitly included.
É correto afirmar que:
(a) The authors of the paper has explored the behavior of a system of interacting particles through
core-softened under confining conditions.
(b) For small values of parameter d* and under confining described in the text above, it is observed
the formation of three layers, only one of them close to the wall.
(c) For large values of parameter d* and under confining described in the text above,, it is observed
the formation of two layers, only one of them close to the wall.
(d) The confining conditions described in the text above does not affect the behavior of water
density anomaly.
(e) None of the options above is correct.
17. Para responder a esta questão, baseie-se no texto a seguir e no rol de conhecimentos cobrados no
Anexo I do Edital que rege a presente seleção de mestrado:
We study a system of N particles with diameter σp confined between two fixed plates. The surfaces
are formed by particles with diameter σw which are organized in a square lattice of area L2 . The
center-to-center plates distance is d∗ = σdp . (...) The particles confined between the two plates
interact through an isotropic effective potential (Fig. 2) given by
6
"
#
σp 12 σp 6
1 r − r0 2
U (r)
−
+ a exp − 2
.
=4
r
r
c
σp
The first term is a standard Lennard-Jones (LJ) 12 − 6 potential with depth plus a Gaussian
centered on radius r = r0 and width c. We used parameters a = 5, r0 /σp = 0.7, and c = 1. The
pressure versus temperature phase diagram of this system in the bulk was studied by Oliveira et
al. They found that a system or particles interacting through this potential exhibits a region in the
pressure-temperature phase diagram where the density and diffusion coefficient are anomalous. This
potential has two length scales with a repulsive shoulder at r/σp ≈ 1 and a very small attractive well
at r/σp ≈ 3.8. Depending on the choice of the parameters a, b, c, and σp , it can represent a whole
family of intermolecular interactions. In this paper we employ a = 5, r0 /σp = 0.7, and c = 1.
É correto afirmar que:
(a) According that model, each particle in the system has radii equal to σp /2.
(b) According that model, each particle in the system has radii equal to σw /2.
(c) Oliveira et al found that a system or particles interacting through the standard Lennard-Jones
(LJ) 12 − 6 potential with depth plus a Gaussian centered on radius r = 2r0 and width c
exhibits a region in the pressure-temperature phase diagram where the density and diffusion
coefficient are anomalous.
(d) That model represents a potential which is always attractive.
(e) None of the options above is correct.
As questões 18 a 20, referentes ao texto 3, intitulado Fluid membrane vesicles in confinement.
Para responder às questões 18 e 19, baseie-se no texto abaixo:
The folding of tissues and membranes plays a dominant role in the interplay between structure
and function in living matter. Countless examples can be given both on the macroscopic (e.g. the
gut [1] or the kidney [2]) and the microscopic level (e.g. the endoplasmic reticulum [3] or the
cytoplasmic membrane [4]). There are various reasons for folding to occur such as differential
growth in tissues [57] or the cooperative action of proteins in lipid membranes [8]. In particular,
the inner membrane of mitochondria is of special interest, since its alteration and remodeling is
closely linked to numerous neurodegenerative diseases [9]. It is found that this membrane consists of
three parts: (i) the inner boundary membrane, which is in close proximity to the surrounding outer
membrane, (ii) the invaginations of the inner membrane inside the interior of the mitochondrion,
also called cristae, and (iii) the cristae junctions, which are narrow tubular necks connecting (i) and
(ii) [10, 11]. Experimental studies of the inner membrane suggest that the structure of the membrane
results from the cooperation of different effects such as surface growth, lipid composition (such as the
concentration of cardiolipin in the membrane [12]) and protein interactions [13, 14]. To disentangle
the different effects, one is urged to search for simple model systems which allow one to understand
the influence of each contribution in a clearly defined way. To reproduce cristae-like deformations
of lipid bilayers experimentally, Khalifat et al [15] and Fournier et al [16] have changed the local pH
gradient of giant unilamellar vesicles. Ponnuswamy et al [17] and Ghochani et al [18] proposed free
energy models for given geometries of a crista junction to predict its size. However, the simplest
and most intuitive way of understanding the generation of membrane invaginations is to consider
the buckling of a closed growing membrane in a constrained volume. Applying this model in a finite
element framework, Renken et al [19] concluded that minimizing the bending energy is sufficient to
provoke invaginations without giving a detailed analysis of the generated shapes.
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18. É correto afirmar que:
(a) Changes in the inner membrane of mitochondria play an important role for understanding any
system where applying finite element framework is possible.
(b) Changes in the inner membrane of mitochondria do not play an important role for understanding
numerous neurodegenerative diseases.
(c) The gut, the kidney, the endoplasmic reticulum and the cytoplasmic membrane are examples
of totally inorganic structures present in living matter.
(d) All the options above are correct.
(e) None of the options above is correct.
19. É correto afirmar que:
(a) Khalifat et al and Fournier et al, respectively in references [15] and [16], changed the local pH
gradient of certain vesicles.
(b) Renken et al, Fournier et al and Ponnusamy et al concluded that minimizing the bending
energy is not sufficient to provoke invaginations.
(c) Experimental studies of the inner membrane suggest that the structure of the membrane results
from the cooperation of different effects such as surface growth, lipid composition (such as the
concentration of cardiolipin in the membrane) and protein interactions.
(d) All the options above are correct.
(e) None of the options above is correct.
20. Para responder a esta questão, baseie-se exclusivamente no texto a seguir que é um trecho das
conclusões do artigo intitulado Fluid membrane vesicles in confinement:
Despite its simplicity, the model is capable of producing a basic set of invaginations which appear
to be the ground states of membrane folding under external confinement. The finer ultrastructural
details in vivo could be due to the local control of the spontaneous curvature and dynamical effects
arising from the hydrodynamical interactions of the fluid membrane with the surrounding viscous
environment. (...) The presented model does not take into account topology changes induced during
the folding process. Our approach, however, could be easily extended to study the result of such a
transition once it occurred by considering a surface with higher genus. Furthermore, it is an open
question if the stabilizing effect of the proteins involved in the cristae formation in vivo could be
macroscopically accounted for by adding an attractive part to the membrane self-contact forces.
É correto afirmar que:
(a) The authors of the paper claim their model can be extended to study the result of folding
process despite of being an complex approach.
(b) The authors of the paper claim that the finer ultrastructural details in vivo could be due to the
local control of the spontaneous curvature and dynamical effects arising from the hydrodynamical interactions of the fluid membrane with the surrounding viscous environment.
(c) The authors of the paper were able to explain, with their model, all the possible questions
related to the system approached.
(d) All the options above are correct.
(e) None of the options above is correct.
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RASCUNHO
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