O efeito fotoelétrico foi descoberto por Hertz no final do século XIX, e a explicação do fenômeno foi dada por Einstein no começo do século XX. Com base nessa explicação, são feitas três afirmações.

I. A energia contida no fóton depende da frequência da radiação incidente.

II. A radiação, ao incidir sobre uma superfície, pode arrancar elétrons desta.

III. A energia cinética do elétron arrancado de uma superfície depende da intensidade da radiação incidente.

Marque a alternativa correta.

Texto base: 11106732

Texto para a questão: As escalas termométricas são utilizadas para medir a temperatura de um corpo ou ambiente. A temperatura é uma grandeza física que representa o nível de agitação das moléculas de um objeto, sendo de grande importância em diversas áreas do conhecimento, como na meteorologia, na física, na medicina e na química, entre outras. As principais escalas termométricas são a Celsius (ou centígrada), a Fahrenheit e a Kelvin. É importante conhecer as escalas termométricas e saber como converter as temperaturas entre elas, para que possamos compreender as informações relacionadas à temperatura de diferentes lugares e situações.

Enunciado:

Qual é a diferença entre as escalas Celsius e Fahrenheit?

O benzeno é um hidrocarboneto aromático presente no petróleo, no carvão e em condensados de gás natural. Seus metabólitos são altamente tóxicos e se depositam na medula óssea e nos tecidos gordurosos. O limite de exposição pode causar anemia, câncer (leucemia) e distúrbios do comportamento. Em termos de reatividade química, quando um eletrófilo se liga ao benzeno, ocorre a formação de um intermediário, o carbocátion. Por fim, ocorre a adição ou substituição eletrofílica.

Com base no texto e no gráfico do progresso da reação apresentada, as estruturas químicas encontradas em I, II e III são, respectivamente:

(UNICENTRO) As substâncias químicas têm propriedades bem definidas e, eventualmente, duas substâncias diferentes podem possuir algumas propriedades iguais, mas não todas elas.Considerando-se essas informações e os dados da tabela que representa algumas propriedades de substâncias químicas, é correto afirmar:

Read this text about Yuri Gagarin.

Yuri was born on March 9, 1934 in Klushino, a small village 100 miles west of Moscow. His father was a cabinetmaker, carpenter, bricklayer, and farmer, and his mother was a milkmaid. Together they worked on a kolkhoz or collective farm. By Soviet social standards, his heritage was impeccable. He was the third of four children. During the war, the Nazis threw his family out of their home and took away two of his sisters. Yuri helped his parents dig a dugout where they lived untill the war was over, then the family moved to Gziatsk. 

[…] 

Yuri was subjected to extremely rigorous training: physical, mental, and psychological. He underwent long periods in a sensory deprivation chamber, experiments with weightlessness, endurance in heat chambers, and test flights under stress with every reaction monitored. […] 

"During the days of preparation for the launch, when everyone had more than his share of concerns, apprehensions, and anxieties, he alone seemed to keep calm. More than that: he was full of good spirits and beamed like the sun." 

On April 12, 1961 the first earthling escaped the gravity well of planet earth. In the spaceship Vostok 1, Senior Lieutenant Yuri Alexeyevich Gagarin orbited earth one time at an altitude of 187 3/4 miles (302 kilometers) for 108 minutes at 18,000 miles an hour. He was the first man to see that the earth was indeed round, indeed mostly water, and indeed magnificent. 

Following his return to earth, Yuri's triumphant walk through Red Square in front of a crowd of hundreds of thousands made him more nervous and afraid than his historic flight. As he reached the podium, the awaiting Valya tearfully whispered in his ear, "Our dream has come true, Yuri." Embracing her he replied, "You're a smart girl! Thank you!" [...]

Russian Archives Online

Disponível em: <http://www.russianarchives.com/gallery/gagarin/>. Acesso em: 19 mar. 2014. (Fragmento)

Rewrite some clauses from the text in just one sentence and set the chronological order for the events according to the text. The beginning of each sentence was given.

A) Yuri helped his parents dig a dugout where they lived / the war was over.

Before the war was over, __________________________________________________________

______________________________________________________________________________

B) Yuri was subjected to extremely rigorous training / He underwent long periods in a sensory deprivation chamber. 

After Yuri had been subjected to extremely rigorous training ______________________________

______________________________________________________________________________

C) Senior Lieutenant Yuri Alexeyevich Gagarin orbited earth one time at an altitude of 187 3/4 miles (302 kilometers) for 108 minutes at 18,000 miles an hour / the first earthling escaped the gravity well of planet earth 

When Senior Lieutenant Yuri Alexeyevich Gagarin orbited earth ___________________________

______________________________________________________________________________

______________________________________________________________________________

D) He reached the podium / the awaiting Valya tearfully whispered in his ear: "Our dream has come true, Yuri." 

After he had reached the podium, ___________________________________________________

______________________________________________________________________________

______________________________________________________________________________