Todas as questões do ENEM

É possível identificar adulterantes do leite de vaca por meio da adição do indicador azul de bromofenol. A presença de agentes oxidantes provoca a descoloração do indicador, mantendo a cor branca na amostra, característica do leite. Substâncias redutoras presentes no leite reagem com o azul de bromofenol, gerando a cor verde. A diminuição do valor de pH do leite torna o indicador amarelo. Em pH mais elevado, o indicador adquire a cor violeta e, em meio neutro, a cor azul. Considere que um lote industrial de leite em embalagem longa vida foi adulterado com excesso de soda cáustica.

Em uma inspeção sanitária do lote adulterado, qual será a cor apresentada pelo leite após adição do indicador azul de bromofenol?

Certa quantidade de gás sofre três transformações sucessivas, A → B, B → C e C → A, conforme o diagrama p-V apresentado na figura abaixo.

A respeito dessas transformações, afirmou-se o seguinte:

I. O trabalho total realizado no ciclo ABCA é nulo.

II. A energia interna do gás no estado C é maior que no estado A.

III. Durante a transformação A՜B, o gás recebe calor e realiza trabalho.

Está correto apenas o que se afirma em

Note e adote:

o gás deve ser tratado como ideal a transformação B →C é isotérmica.

Reflorestamento é uma ação ambiental que visa repovoar áreas que tiveram a vegetação removida. Uma empresa deseja fazer um replantio de árvores e dispõe de cinco produtos que podem ser utilizados para corrigir o pH do solo que se encontra básico. As substâncias presentes nos produtos disponíveis são: CH3COONa, NH4Cl, NaBr, NaOH e KCl.

A substância a ser adicionada ao solo para neutralizá-lo é

Utilize as informações a seguir para responder à questão.

Um trem em alta velocidade desloca-se ao longo de um trecho retilíneo a uma velocidade constante de 108 km/h. Um passageiro em repouso arremessa horizontalmente ao piso do vagão, de uma altura de 1 m, na mesma direção e sentido do deslocamento do trem, uma bola de borracha que atinge esse piso a uma distância de 5 m do ponto de arremesso.

A figura abaixo mostra o gráfico da energia potencial gravitacional U de uma esfera em uma pista, em função da componente horizontal x da posição da esfera na pista.

A esfera é colocada em repouso na pista, na posição de abscissa x = x1, tendo energia mecânica E < 0. A partir dessa condição, sua energia cinética tem valor

Note e adote:

desconsidere efeitos dissipativos.

Entre os materiais mais usados no nosso dia a dia destacam-se os plásticos, constituídos por polímeros. A consequência de seu amplo uso é a geração de resíduos, que necessitam de um destino final adequado em termos ambientais. Uma das alternativas tem sido a reciclagem, que deve respeitar as características dos polímeros que compõem o material. Esse processo envolve algumas etapas, como: separação do resíduo (catação), moagem, hidrólise, lavagem, secagem, pirólise e aquecimento (fusão).

SPINACÉ, M. A. S., PAOLI, M. A. D. Tecnologia de reciclagem de polímeros. Química Nova, n.1, 2005 (adaptado).

Quais das etapas citadas do processo de reciclagem são classificadas como métodos químicos?

A figura acima mostra parte do teclado de um piano. Os valores das frequências das notas sucessivas, incluindo os sustenidos, representados pelo símbolo #, obedecem a uma progressão geométrica crescente da esquerda para a direita; a razão entre as frequências de duas notas Dó consecutivas vale 2; a frequência da nota Lá do teclado da figura é 440 Hz. O comprimento de onda, no ar, da nota Sol indicada na figura é próximo de

Note e adote:

21/12 = 1,059

(1,059)2 = 1,12

velocidade do som no ar = 340 m/s

TEXT

The need to constantly adapt is the new reality for many workers, well beyond the information technology business. Car mechanics, librarians, doctors, Hollywood special effects designers — virtually everyone whose job is touched by computing — are being forced to find new, more efficient ways to learn as retooling becomes increasingly important not just to change careers, but simply to stay competitive on their chosen path.

Going back to school for months or years is not realistic for many workers, who are often left to figure out for themselves what new skills will make them more valuable, or just keep them from obsolescence. In their quest to occupy a useful niche, they are turning to bite-size instructional videos, peer-to-peer forums and virtual college courses.

Lynda Gratton, a professor of management practice at the London Business School, has coined a term for this necessity: “serial mastery.”

“You can’t expect that what you’ve become a master in will keep you valuable throughout the whole of your career, and you want to add to that the fact that most people are now going to be working into their 70s,” she said, adding that workers must try to choose specialties that cannot be outsourced or automated. “Being a generalist is, in my view, very unwise. Your major competitor is Wikipedia or Google.”

Businesses have responded by pouring more money into training, even in the current economic doldrums, according to several measures. They have experimented by paying employees to share their expertise in internal social networks, creating video games that teach and, human resources consultants say, enticing employees with tuition help even if they leave the company.

Individuals have also shouldered a lot of responsibility for their own upgrades. Lynda.com, which charges $25 a month for access to training videos on topics like the latest version of Photoshop, says its base of individual customers has been growing 42 percent a year since 2008. Online universities like Udacity and Coursera are on pace to double in size in a year, according to Josh Bersin of Bersin & Associates, a consulting firm that specializes in learning and talent management. The number of doctors participating in continuing education programs has more than doubled in the last decade, with the vast majority of the growth stemming from the increased popularity of Internet-based activities, according to the Accreditation Council for Continuing Medical Education in Chicago.

The struggle is not just to keep up, but to anticipate a future of rapid change. When the AshevilleBuncombe Technical Community College in North Carolina wanted to start a program for developing smartphone and tablet apps, the faculty had to consider the name carefully. “We had this title Mobile Applications, and then we realized that it may not be apps in two years, it may be something else,” said Pamela Silvers, the chairwoman of the business computer technologies department. “So we changed it to Mobile Development.”

As the metadata and digital archivist at Emory University, Elizabeth Russey Roke, 35, has had to keep up with evolving standards that help different databases share information, learn how to archive “born digital” materials, and use computers to bring literary and social connections among different collections to life. The bulk of her learning has been on the job, supplemented by the occasional course or videos on Lynda.com.

“For me, it’s easier to learn something in the classroom than it is on my own,” she said. “But I can’t exactly afford another three years of library school.”

Rapid change is a challenge for traditional universities; textbooks and even journals often lag too far behind the curve to be of help, said Kunal Mehta, a Ph.D. student in bioengineering at Stanford University. His field is so new, and changing so rapidly, he said, that there is little consensus on established practices or necessary skills. “It’s more difficult to know what we should learn,” he said. “We have advisers that we work with, but a lot of times they don’t know any better than us what’s going to happen in the future.” 

Instead, Mr. Mehta, 26, spends a lot of time comparing notes with others in his field, just as many professionals turn to their peers to help them stay current. The International Automotive Technicians Network, where mechanics pay $15 a month to trade tips on repairs, has more than 75,000 active users today, up from 48,000 in 2006, said Scott Brown, the president. 

In an economy where new, specialized knowledge is worth so much, it may seem anticompetitive to share expertise. But many professionals say they don’t see it that way. 

“We’re scattered all over the country, Australia, New Zealand, the U.K., so it never really bothered us that we were sharing the secrets of what we do,” said Bill Moss, whose repair shop in Warrenton, Va., specializes in European cars, and who is a frequent user of peer-to-peer forums. 

Mr. Moss, 55, said technological advances and proprietary diagnostic tools had forced many garages to specialize. Ten years ago, if his business had hit a slow patch, he said, he would have been quicker to broaden his repertory. “I might have looked at other brands and said, ‘These cars aren’t so bad.’ That’s much harder to do now, based on technology and equipment requirements.” His training budget is about $4,000 a year for each repair technician. 

Learning curves are not always driven by technology. Managers have to deal with different cultures, different time zones and different generations as well as changing attitudes. As medical director of the Reproductive Science Center of New England, Dr. Samuel C. Pang has used patient focus groups and sensitivity training to help the staff adjust to treating lesbian couples, gay male couples, and transgendered couples who want to have children. This has given the clinic a competitive advantage. 

“We have had several male couples and lesbian couples come to our program from our competitors’ program because they said they didn’t feel comfortable there,” Dr. Pang said. 

On top of that, he has to master constantly evolving technology. “The amount of information that I learned in medical school is minuscule,” he said, “compared to what is out there now.” 

 http://www.nytimes.com/2012/09/22

TEXT

The need to constantly adapt is the new reality for many workers, well beyond the information technology business. Car mechanics, librarians, doctors, Hollywood special effects designers — virtually everyone whose job is touched by computing — are being forced to find new, more efficient ways to learn as retooling becomes increasingly important not just to change careers, but simply to stay competitive on their chosen path.

Going back to school for months or years is not realistic for many workers, who are often left to figure out for themselves what new skills will make them more valuable, or just keep them from obsolescence. In their quest to occupy a useful niche, they are turning to bite-size instructional videos, peer-to-peer forums and virtual college courses.

Lynda Gratton, a professor of management practice at the London Business School, has coined a term for this necessity: “serial mastery.”

“You can’t expect that what you’ve become a master in will keep you valuable throughout the whole of your career, and you want to add to that the fact that most people are now going to be working into their 70s,” she said, adding that workers must try to choose specialties that cannot be outsourced or automated. “Being a generalist is, in my view, very unwise. Your major competitor is Wikipedia or Google.”

Businesses have responded by pouring more money into training, even in the current economic doldrums, according to several measures. They have experimented by paying employees to share their expertise in internal social networks, creating video games that teach and, human resources consultants say, enticing employees with tuition help even if they leave the company.

Individuals have also shouldered a lot of responsibility for their own upgrades. Lynda.com, which charges $25 a month for access to training videos on topics like the latest version of Photoshop, says its base of individual customers has been growing 42 percent a year since 2008. Online universities like Udacity and Coursera are on pace to double in size in a year, according to Josh Bersin of Bersin & Associates, a consulting firm that specializes in learning and talent management. The number of doctors participating in continuing education programs has more than doubled in the last decade, with the vast majority of the growth stemming from the increased popularity of Internet-based activities, according to the Accreditation Council for Continuing Medical Education in Chicago.

The struggle is not just to keep up, but to anticipate a future of rapid change. When the AshevilleBuncombe Technical Community College in North Carolina wanted to start a program for developing smartphone and tablet apps, the faculty had to consider the name carefully. “We had this title Mobile Applications, and then we realized that it may not be apps in two years, it may be something else,” said Pamela Silvers, the chairwoman of the business computer technologies department. “So we changed it to Mobile Development.”

As the metadata and digital archivist at Emory University, Elizabeth Russey Roke, 35, has had to keep up with evolving standards that help different databases share information, learn how to archive “born digital” materials, and use computers to bring literary and social connections among different collections to life. The bulk of her learning has been on the job, supplemented by the occasional course or videos on Lynda.com.

“For me, it’s easier to learn something in the classroom than it is on my own,” she said. “But I can’t exactly afford another three years of library school.”

Rapid change is a challenge for traditional universities; textbooks and even journals often lag too far behind the curve to be of help, said Kunal Mehta, a Ph.D. student in bioengineering at Stanford University. His field is so new, and changing so rapidly, he said, that there is little consensus on established practices or necessary skills. “It’s more difficult to know what we should learn,” he said. “We have advisers that we work with, but a lot of times they don’t know any better than us what’s going to happen in the future.” 

Instead, Mr. Mehta, 26, spends a lot of time comparing notes with others in his field, just as many professionals turn to their peers to help them stay current. The International Automotive Technicians Network, where mechanics pay $15 a month to trade tips on repairs, has more than 75,000 active users today, up from 48,000 in 2006, said Scott Brown, the president. 

In an economy where new, specialized knowledge is worth so much, it may seem anticompetitive to share expertise. But many professionals say they don’t see it that way. 

“We’re scattered all over the country, Australia, New Zealand, the U.K., so it never really bothered us that we were sharing the secrets of what we do,” said Bill Moss, whose repair shop in Warrenton, Va., specializes in European cars, and who is a frequent user of peer-to-peer forums. 

Mr. Moss, 55, said technological advances and proprietary diagnostic tools had forced many garages to specialize. Ten years ago, if his business had hit a slow patch, he said, he would have been quicker to broaden his repertory. “I might have looked at other brands and said, ‘These cars aren’t so bad.’ That’s much harder to do now, based on technology and equipment requirements.” His training budget is about $4,000 a year for each repair technician. 

Learning curves are not always driven by technology. Managers have to deal with different cultures, different time zones and different generations as well as changing attitudes. As medical director of the Reproductive Science Center of New England, Dr. Samuel C. Pang has used patient focus groups and sensitivity training to help the staff adjust to treating lesbian couples, gay male couples, and transgendered couples who want to have children. This has given the clinic a competitive advantage. 

“We have had several male couples and lesbian couples come to our program from our competitors’ program because they said they didn’t feel comfortable there,” Dr. Pang said. 

On top of that, he has to master constantly evolving technology. “The amount of information that I learned in medical school is minuscule,” he said, “compared to what is out there now.” 

 http://www.nytimes.com/2012/09/22