Today glass use for things such as windows

Glass is a substance made from sand, limestone, and soda, which are combined and heated to 1500 degrees Celsius. As the mixture cools, it becomes very thick and eventually becomes solid. Historians believe that the ancient Egyptians invented glass. Archeologists have found 5,000-year-old glass beads there. About 100 B.C., Syrian craftsmen learned how to make hollow pots or vases by blowing air into molten glass through a long, narrow iron tube.

The Romans used this glass-blowing technique to create beautiful artwork. They also found a way to make glass for windows. After the fall of the Roman Empire, glass-making declined for several centuries. It was revived in the 8th century in the Middle East and soon spread to other parts of the world. In the 15th century, glassmakers in Venice, Italy, discovered how to make clear glass (crystal). Until then, glass had impurities in it. Venice became famous for its exquisite glass bottles and still is today.

Several Venetian craftsmen took their trade to other parts of Europe, such as Germany, where beautiful Bohemian glassware is made. In the 17th century, lead crystal glass was invented. This much-improved material was used in optical lenses, telescopes, and microscopes. Machines that could make glass bottles began to appear in the late 1880s. In 1907, Michael Owens, an American, invented a machine that produced 2,500 bottles every hour. Since then, many scientific  discoveries have improved the quality of glass and how it is produced and have found new uses for it.

Today, glass is used for things such as windows and light bulbs, kitchenware, insulation , and sophisticated scientific equipment. Thousands of products, from wine to cosmetics, are packaged in glass containers. Fortunately, because it takes less energy to melt recycled glass than to make new glass, glass is considered to be an environmentally friendly material.

Pre-Reading Warm Up Questions

1. Do you know how glass is made?
2. Who do you think invented glass?
3. What does an archeologist do?
4. Do you know what city is world famous for its beautiful glass-making?
5. What is an “environmentally friendly” product?

ПРОМЕЖУТОЧНАЯ
АТТЕСТАЦИЯ

по
английскому языку

8 
класс

1.      
Назначение
работы – представляет
собой форму объективной оценки качества подготовки лиц, осваивающих
образовательные программы основного общего образования, с использованием
заданий стандартизированной формы (контрольных измерительных материалов).
Контрольные измерительные материалы позволяют установить уровень освоения
учащимися 8 класса ФГОС ООО.

Результаты работы могут быть использованы
для организации занятий по коррекции видов деятельности обучающихся с целью
формирования предметных и метапредметных УУД.

2.      Документы,
определяющие содержание КИМ

Содержание
итоговой работы определяет ФГОС ООО и примерные программы по английскому
языку.

3.      Характеристика
структуры и содержания работы

Экзаменационная
работа состоит из письменной части — разделы, включающие задания по аудированию,
чтению, а также задания на контроль лексико-грамматических навыков.

В
работу по иностранному языку включены 3 задания с кратким ответом (раздел 1
«Задания по аудированию», раздел 2 «Задания по чтению», раздел 3 «Задания по
грамматике и лексике»).

В КИМах
предложены следующие разновидности заданий с кратким ответом:

—       
задания
на установление соответствия позиций, представленных в двух множествах;

—       
задания
на выбор и запись правильного ответа из предложенного перечня ответов;

—       
задания 
на  заполнение  пропуска  в  связном  тексте  путем преобразования предложенной
начальной формы слова в нужную грамматическую форму;

—       
задания 
на  заполнение  пропуска  в  связном  тексте  путем образования  родственного 
слова  от  предложенного  опорного слова.

На
задания с кратким ответом ответ дается соответствующей записью в  виде  цифры 
или  последовательности  цифр,  записанных  без  пробелов и  других 
разделителей  или  слова/словосочетания,  записанного/записанных также без
пробелов и других разделителей.       

Рекомендуемое
время выполнения работы – 45 минут.

Рекомендуемое
время выполнения заданий отдельных разделов:

раздел 1
(задания по аудированию) – 15 минут;

раздел 2
(задание по чтению) – 15 минут;

раздел 3
(задания по грамматике и лексике) – 15 минут.

            За
верное выполнение каждого задания с выбором ответа и с кратким ответом учащийся
получает 1 балл. Если в кратком ответе сделана орфографическая ошибка, ответ
считается неверным. За неверный ответ или отсутствие ответа выставляется 0
баллов.

            За 
выполнение  задания  1 учащийся может получить от 0 до 4 баллов; за задание 2 –
от 0 до 7 баллов; за задание 3 – от 0 до 9 баллов; за задание 4 – от 0 до 6
баллов / Максимальное количество баллов, которое может набрать учащийся за
выполнение работы,  –  26.

КРИТЕРИИ
ОЦЕНИВАНИЯ ВЫПОЛНЕНИЯ ЗАДАНИЙ

промежуточной
аттестации

по
английскому языку

8
класс

Критерии
оценивания письменных работ по предмету «Английский язык»

За
письменные работы (контрольные работы, тестовые работы, словарные диктанты)
оценка вычисляется исходя из процента правильных ответов:

КИМы
для проведения промежуточной аттестации

                                           по
английскому языку за курс 8 класса

за
2017-2018 учебный год

I
вариант

LISTENING

Задание 1 

Вы услышите четыре коротких диалога, обозначенных А, B, C и D.
Определите, где происходит каждый из этих диалогов. Используйте каждое место
действия из списка 1–5 только один раз. В задании есть одно лишнее место
действия. Вы услышите запись дважды. Занесите свои ответы в таблицу.

 1.
At the museum

2. In
the restaurant

3. In
the street

4. At
driving school

5. In
the camp

READING

Задание 2

Прочитайте тексты и установите соответствие между текстами А–G и
заголовками 1–8. В ответ запишите цифры, в порядке, соответствующем буквам.
Используйте каждую цифру только один раз. В задании
есть один лишний заголовок.

1. My accommodation
in Rome

2. New
friends

3.
Getting the job

4. The
working day

5.
Plans for the next summer

6.
Language experience

7. The
top tourist attraction

8.
General impression of the country

A. I’ve
just returned from Italy, and it was the most beautiful working holiday anyone
could dream of. Yes, I saw the Colosseum with my own eyes! It was built in the
first century AD — the amphitheatre could house as many as 50,000 people. It’s
difficult to imagine the gladiators fighting there and the public watching the
cruel show. Thpre were also fights with lions. Fortunately, there are no lions
in the Colosseum now — only cats. And there are a lot of them! 

B. The Colosseum was the first thing I wanted to see in Rome, but not
the only one that impressed me. I used my camera a lot — Italy is a country
with a great cultural heritage. Apart from the views, Italy is a country of
delicious food — I’ve never eaten such gorgeous pizzas! I’d have certainly put
on some weight if I hadn’t had to walk such a lot — we were saving on transport
because Italy is an expensive country.

C. It took us thirty-five minutes every morning to get from the
hostel where we were staying to the pizzeria we were working. Our room was very
small, it had a poor view, just the house opposite, but that wasn’t a problem —
we didn’t spend much time there anyway, We had only the basics in our room- two
beds, hangers for clothes, a little table and one chair. There was a laundry
downstairs and a shared kitchen to prepare meals.

D. As for the kitchen, we didn’t use it much — we ate at work! Our
working day started at 9 am and lasted till 9 pm. We had a long siesta (a break
between two and five in the afternoon) which we used for sightseeing in spite
of the heat. And in the evening there were usually lots of customers and we had
to be quick and attentive so as not to confuse their orders. We felt absolutely
exhausted when we came home.

E. Anyway we felt privileged to have got the job. It was Anna, my
best friend, who suggested working holidays in Italy. She found the vacancies
and sent our CVs to the manager. At first I didn’t know what to say as I wasn’t
sure I wanted to work in summer. But on the other hand, the idea of earning my
own money and seeing Italy was very attractive.

F. I’m glad I agreed to Anna’s suggestion — we enjoyed living in a
new country and meeting new people. Italians are very sociable and easy-going.
Our fellow workers showed us lots of interesting places and it was fun to
explore the country together. Anna and I really hope that they’ll come to
Britain one day and we’ll be able to show them our country, too. We are going
to keep in touch.

G. We
didn’t know Italian when we went there. Some people in the pizzeria spoke
English and they helped us a lot. Two weeks later we were able to understand
what the customers were asking us about and we spoke basic Italian to them.
Italian is beautiful — I like how it sounds and it’s not at all difficult. We
plan to go on learning it in case we want to work in the pizzeria again.

GRAMMAR
AND VOCABULARY

Задание 3

Прочитайте приведённый ниже текст. Преобразуйте слово,
напечатанное заглавными буквами в скобках так, чтобы оно грамматически
соответствовало содержанию текста. Заполните пропуск
полученным словом.

Glass is a substance _____ (MAKE) from a combination of  sand,
limestone, and soda, which is heated to 1500 degrees Celsius. As the mixture
cools, it ____(BECOME) very thick and  eventually turns to a solid substance.
Historians believe that ancient Egyptians were the ____ (ONE) to invent glass.
Recently archeologists ____ (FIND) 5,000-year-old glass beads in Egypt. In about 100 B.C.,
Syrian craftsmen learned how to make hollow pots or vases by ____ (BLOW)     
air into molten glass through a long, narrow iron tube. The Romans used this
technique to create beautiful artwork. They also found a way to make glass for
windows in         ____ (THEY) houses. Today glass _____ (USE) for things such
as windows, light bulbs, kitchenware, and sophisticated scientific equipment.
_____(THOUSAND) of products, from wine to cosmetics, are packaged in glass
containers. It is difficult       _____ (IMAGINE) modem life without glass.

Задание 4

Прочитайте приведённый
ниже текст. Преобразуйте слово, напечатанное заглавными буквами в скобках так,
чтобы оно грамматически соответствовало содержанию текста. Заполните
пропуск полученным
словом.

The next time you buy something made from rubber — waterproof
boots, car tires — try to figure out if synthetic or natural rubber was used.
Natural rubber is extracted from rubber trees. Rubber trees originated on the
South American continent, and _____ (EUROPE) explorers brought them to Asia in
the 19^th century. Today, the ____ (MAJOR) of natural rubber comes
from three countries: Thailand, Indonesia, and Malaysia. Commercial rubber
trees _____ (USUAL) grow in large plantations, and a single rubber tree will
produce rubber for about 25 years. Rubber trees require warm temperatures, high
____ (HUMID), and plenty of sunshine. Another name for rubber is latex.
____(FORTUNATE) some people are allergic to latex. That’s why they should be
very _____ (CARE) never to use any rubber products.

КИМы
для проведения промежуточной аттестации

                                           по
английскому языку за курс 8 класса

за
2017-2018 учебный год

II
вариант

LISTENING

Задание 1 

Вы услышите четыре коротких диалога, обозначенных А, B, C и D.
Определите, где происходит каждый из этих диалогов. Используйте каждое место
действия из списка 1–5 только один раз. В задании есть одно лишнее место
действия. Вы услышите запись дважды. Занесите свои ответы в таблицу.

1.
at the hospital

2. in
the office

3. at
the airport

4. at
home

5. at
school

READING

Задание 2

Прочитайте тексты и установите соответствие между текстами А–G и
заголовками 1–8. В ответ запишите цифры, в порядке, соответствующем буквам.
Используйте каждую цифру только один раз. В задании
есть один лишний заголовок.

1. A
vital necessity

2.
Following the tradition

3.
Everyday duty

4. An
easy beginning

5.
Care for monkey

6. An
obedient animal

7.
Devoted helpers

8.
Ways of training

A. Monkeys
are very intelligent animals. In fact, some smart monkeys even go to college!
The monkeys at the Monkey Training School in Surat Thani, Thailand, are sent
there by farmers to learn an important job: how to pick coconuts from very tall
trees. Nowadays, there are about 12,000 monkeys in Surat Thani are working to
pick coconuts, helping humans, because if the people climb up those high trees,
they can fall and die.

B. Trainer
Somporn Saewkwo says it takes months for the young monkeys to learn the
strategy for picking coconuts. For the first month, he just lets the monkey
play. He shows him to spin a coconut in a box. Then he holds the monkey’s hand
and encourages him to twist the coconut himself. Later, he brings the monkey to
a tree and lets him learn how to pick the coconuts that are ready to eat.

C. Step
by step, the monkey goes higher and higher. The trainer uses a rope to control
and direct the monkey’s work. The monkey goes left, right, up and down. When Somporn
pull the rope, the monkey goes faster. In the past, everyone was training
monkeys in different way — some people were hurting the monkeys. Trainer
Somporn Saewkwo created a different, more gentle method of teaching monkeys,
which is now used by others at the monkey training college.

D. Monkeys
have been helping Thai farmers to pick coconuts for more than a hundred years.
The monkeys climb trees and twist coconuts with their hands until the fruit
falls to the ground. The coconut is an important fruit for farmers here. Farmer
can earn about two dollars for every hundred coconuts that they bring to
market. People buy the fruit on Thai beaches, and it’s also used in the
country’s popular coconut curry. About 2 ml. are produced each month in
Thailand. And many farmers say they couldn’t pick the fruit without help from
their monkeys.

E. Pak
Dee’s three-year-old monkey assists with his work. The monkey picks fruit from
Pak’s own trees. Pak also lends the monkey to other farmers to earn extra
money. The animal is so valuable that Pak never leaves it home alone. The
monkey could run away or somebody could take it.

F. Pak
Dee describes the system he uses. He ties the monkey to a coconut tree near the
house. He gives him rice to eat, sometimes with curry. The monkey can live to
be 13 years old, so he has ten more years that he can work. Farmer says that
because the monkeys are so important to them, most are well cared for and don’t
have a hard life.

G. Because
a lot of Thailand’s forests have disappeared, more and more monkeys now need
man’s help to be able to live. All the monkeys that come to stay with them have
a better living than in the jungle. One side does not have an advantage over
the other. As long as Thailand continues to produce coconuts, these farmers
will probably continue to use monkeys. You see, the monkey and the coconut will
be together always.

GRAMMAR AND VOCABULARY

Задание 3

Прочитайте приведённый ниже текст. Преобразуйте слово,
напечатанное заглавными буквами в скобках так, чтобы оно грамматически
соответствовало содержанию текста. Заполните пропуск
полученным словом.

Our family was quite small, just my Mom, Dad and me. I had no brothers
or sisters. When I was ten, my parents finally decided I ____ (CAN) have a dog.
I’ve been dreaming of ____ (HAVE) a dog for  years, but my parents used to say
“ No, you ____ (NOT BE) responsible enough to take care of a dog yet.” Finally
they decided I was ready! So one day, my mother ____ (DRIVE) me to the pound.
That was a special place out of town where lost dogs ____ (TAKE). There were
dozens of dogs there. They were different in size and colour and all of  ____
(THEY) were jumping and barking in their cages. But one dog was sitting in a
corner, nervously ____ (LOOK) around. _____ (WE) eyes met! And I knew that was
the dog for me! I’ll never forget that day, the day when I got my ___ (ONE) dog
ever!

Задание 4

Прочитайте приведённый ниже текст. Преобразуйте слово,
напечатанное заглавными буквами в скобках так, чтобы оно грамматически
соответствовало содержанию текста. Заполните пропуск
полученным словом.

Aesop was a famous ____ (GREECE) folk hero who lived in the 6^th
century BC. He is now well- known as a ____ (WRITE) of animal fables. Through
these many fables Aesop showed the wise and ____ (FOOL) bahaviour of men. Not
much is known about the life of Aesop. It is believed he was born in Thrace,
Greece and knew what ____ (SLAVE) was on his own experience. It is said that
his ____ (WISE) delighted one of his masters that the slave was given ____
(FREE).

Слайд 1

READING For questions 1- 8, read the text below and decide which answer best fits each gap. The Karakamia reserve is located not far from Perth in Western Australia. Suburban is not usually a word that you ( 1 ) with a wildlife paradise, but Karakamia is actually part of the township of Chidlow . The land was purchased by the Australian government in 1991 with the ( 2 ) of protecting threatened species of indigenous wildlife. That’s why there is a nine- kilometre fence around it, designed to ( 3 ) out species introduced by Europe an settlers, ( 4 ) foxes, cats and rabbits. The sanctuary ( 5 ) its name from the Aboriginal word meaning ‘home of the redtailed black cockatoos’, and at dusk the air is ( 6 ) with the calls of these birds. This is when the sanctuary is at its most magical. A guided walk by spotlight is the perfect way to experience it. Many of the animals are quite tame, which means you can ( 7 ) them at close quarters and get an idea of what Australia was like ( 8 ) to European colonisation . 1 A refer B accompany C regard D associate 2 A proposal B aim C target D plan 3 A catch B send C keep D hold 4 A including B intending C involving D indicating 5 A bears B finds C gains D takes 6 A crowded B filled C completed D packed 7 A observe B notice C realise D glance 8 A advance B former C ahead D prior

Слайд 2

1-D/ associate 2-B/ aim 2-C/ keep 4-A/ including 5-D/ takes 6-B/ filled 7-A/ observe 8-D/ prior

Слайд 3

For questions 9 – 16, read the text below and think of the word wich best fits each gap. Use only one word in each gap. There is an example at the beginning. In the exam, write your answers IN CAPITAL LETTERS on the separate answer sheet. Example: 0 NUMBER Spot the gorilla The gorilla experiment is famous in modern psychology. Participants are asked to watch a video of friends playing an informal game of ball and count the (0) …….. of times the ball is passed from one player to (9)… . The entire game and all the players are visible on screen throughout the experiment, and only one camera was used to film it. Halfway through the game, someone wearing a gorilla costume walks into the shot and begins to (10)…. part in the game. The figure’ remains on screen for around nine seconds. The strange thing is that the viewers are (11)…. busy counting the number of passes that around half of (12) …. regularly fail to notice the gorilla (13)…. all. (14) …. these people are told about the gorilla, they are amazed to think they could (15) …. missed it. The experiment works every time, but why some people see the gorilla and others don’t remains a mystery. Indeed, researchers have never been able to predict which participants (16) …. see the gorilla.

Слайд 4

9- another . 10- take 11-so 12-them 13-at 14-When 15-have 16-will

Слайд 5

For questions 17 – 24, read the text below. Use the word given in capitals at the end of some of the lines to form a word that fits in the gap in the same line. There is an example at the beginning. Example: (0) BEGINNINGS Review of The Porsche Book Many of the world’s biggest brand names had very humble (0 BEGIN) …. The car manufacturer Porsche is no (17 EXCEPT ) … Whether you are a fan of fast sports cars or not, reading about the (18 GROW) … of a small business into a large internationally renowned company makes for interesting reading. This is the story of the company’s rise to fame and covers eight decades and the book includes a wonderful (19 COLLECT)…. of two hundred glossy photographs, including what is (20 SURE)…. one of the most famous cars ever: the shiny Porsche 718 that will be forever associated with the (21 LEGEND) …. actor James Dean, who famously crashed one in 1955. This is a very classy coffee table book that is both (22 ENJOY) …. and informative. It isn’t cheap at £85, but if you are a fan of (23 GLAMOUR) …. sports cars, you may well find it (24 POSSIBLE) …. to resist.

Слайд 6

17- exception 18-growth 19-collection 20-surely 21- legendary 22- enjoyable 23- glamorous 24-impossible

Слайд 7

For questions 25-30, complete the second sentence so that it has a similar meaning to the first sentence, using the word given. Do not change the word given. You must use between two and five words, including the word given. Example: What type of music do you like best? FAVOURITE What ______________________________ type of music? Example: 0 IS YOUR FAVOURITE 25. John qualified as an instructor three years ago. BEEN John instructor for three years. 26. Although we thought the minibus would be comfortable, we were mistaken. TURN The minibus did as comfortable as we had expected. 27. The tour bus stopped frequently to let people admire the view. THAT The tour bus stopped frequently admire the view. 28. Faye hadn’t finished her dinner when Steve called her. STILL Faye when Steve called her. 29. It’s getting late, so I ought to go home’, said Zoe. BETTER Zoe said it was getting late and that home. 30. Sandra’s sister can ski better than she can. SKIER Sandra is as her sister.

Слайд 8

25- has been qualified as an 26-not turn out to be 27- so that people could 28- was still eating/having/finishing her dinner 29-she had better go 30- not such a good skier

Слайд 9

You are going to read an article about a mountain climber. Six sentences have been removed from the article. Choose from the sentences A-G the one which fits each gap (37 – 42). There is one extra sentence which you do not need to use. In the exam, mark your answers on the separate answer sheet. I run up mountains Mountain climbing hasn’t developed much in the past fifty years or so, but I want to introduce a new style. I call it ‘ skyrunning ‘. It means climbing high mountains as fast as possible and using as little equipment as possible. Skyrunning is the most honest kind of mountaineering. Some years ago, I decided to climb Mount Aconcagua, in the Andes, which usually takes three days. I didn’t have that sort of time — so I thought about how it could be done more quickly. In the end, I managed it in four hours and twenty-five minutes. Since then I’ve climbed several mountains this way, including the ‘seven summits’, the highest mountains on each continent. ( 37)… When I climbed Mount Everest, the only nutrition I took with me was carbohydrate gels, salted crackers and about three litters of rosehip tea. It took me sixteen hours and forty-two minutes to go up — a new speed record on the northern route. I have also set speed records on Antarctica’s Mount Vinson, the Carstensz Pyramid in New Guinea and other summits. Attempts such as these need months of training and preparation, as with any serious sport. To build up strength, I sometimes haul an enormous tractor tyre behind me while running uphill. ( 38)… I I call it ‘the beast’ because of the aggressive energy I build up during these training sessions. The psychological side of training is as important as the physical. I use foreign languages to affect my mental state and enhance my performance. I shout things out in these, even though I know there’s nobody to hear me. I’m Austrian and speak only a few words of the Russian language. ( 39)… I couldn’t tell you why that should be the case. Whereas Russian is full of energy and strength, English is a language that calms me and helps me to focus. Two years ago, I was climbing in Nepal and knew that I was in danger from avalanches. I noticed that I kept saying to myself: ‘Hey man, take care!’ ( 40)… It was as if one part of me had stepped outside myself to make sure I made the right decisions, and that phrase helped. For other people, this might sound ridiculous, but I don’t care. In high altitudes, any mistake can be lethal, and I know how it feels to face death. Seventeen years ago, when I was twenty-four, I was climbing with a friend in the Karakoram mountains in Pakistan at about 18,000 feet. ( 41) … It was the sound of an avalanche, which hit us and broke my right thighbone. My friend pulled me out of the snow, but although we had survived, we realised he wouldn’t be able to drag me back to the base camp. I said: ‘Go, just leave me here.’ And he left me behind. I lay alone in the mountains for days. Sometimes I hallucinated, other times I shouted. ( 42) …. I Finally, my friend came back with other climbers and saved me. I thought extreme mountaineering was too risky at first, but slowly my perspective changed. There are so many mountains to climb, but I know my records won’t last forever. In ten or twenty years, skyrunning will be established as a sport. I see myself as a pioneer.

Слайд 10

A All kinds of song I’d never thought twice about ran through my mind. B I can drag this for four hours at a time. C I couldn’t stop repeating that. D I managed to get up all of those without any oxygen or tents. E lt’s the one I use when I need to push forward through heavy snow, however. F Suddenly, there was an incredible rumble up above us. G These clearly came as quite shock

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37-d 38-b 39-e 40-c 41-f 42-a

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You are going to read an article about people who gave up their jobs to start their own business. For questions 43 – 52, choose from the people (A – D). The people may be chosen more than once. Which person mentions how good it is being able to make your own decisions? 43 enjoys seeing employees making a success of things? 44 had to solve a technical problem before launching the business? 45 is surprised to have attracted such a wide variety of clients? 46 is happy to have received positive feedback from clients? 47 sometimes feels anxious about financial aspects of the business? 48 took time to decide what type of business to start? 49 was able to draw on experience gained in a similar working situation? 50 was keen to make use of a wide range of existing skills? 51 was keen to work on a more personal level with clients? 52

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Starting your own business We talked to four people who gave up working for somebody else and started their own business A Beautician I had to rethink my future when the multi-national company I worked for as a marketing executive decided to move my job to the USA. My life back then, wearing designer clothes and taking regular long-haul Bights, couldn’t be more different from today. Well, I wanted a job where I’d have the chance to interact with people more, and saw a gap in the market for a beauty salon locally. Working for yourself is great as you can make your own mind up about things and you aren’t driven by someone else about when and how you do that. But the flipside is that there’s nobody to share the burden with when you wake up in the middle of the night worrying about how you’re going to pay the rent. But I have no regrets. B Gym owner After seventeen years working in banking, I wanted to try something totally different. A business that used a combination of my financial, sporting and parenting experience, but which didn’t involve such long exhausting hours at the office appealed to me a great deal. I came across the concept behind The Little Gym by accident when I was surfing the Internet. It’s a novel concept that had gone down really well in the USA. It caters for children from four months to twelve years, giving them good-quality physical instruction and a cerebral work-out at the same time. Having control of my own life is a definite high, as is seeing my staff doing a good job. Every day is different, so it’s never boring. C Caterer I worked for a big international company, but was no longer finding it rewarding. I’d completed twenty years’ service, so I had some money saved up, but not enough to retire on. But I took six months off’ and we went to stay with my wife’s family in Spain. It was a good opportunity to ponder the question: ‘What next?’ That’s when we got the idea for Tapas in a Box. We were in a bar eating the local Spanish food called ‘tapas’ and I thought: ‘This would be perfect for people back home who want to have a great, relaxed time with friends, without spending ages cooking.’ The challenge was then to work out how to deliver the mix of foods all at once, because tapas include things like raw almonds and chilled cheeses as well as the hot things that need heating in an oven. Once we’d cracked that, we were up and running. I can’t stress too much the thrill you feel when a customer tells you they’ve had a great time. The sense of having gone from a new idea to actually delivering something good is very motivating. D Virtual PA I’d been a secretary and personal assistant (PA) for twenty years and had begun to dread the thought that I’d be at the same desk until I retired. When the company announced that its European office was to close, I could’ve taken a drop in salary and found another job locally, but decided to set up my own business instead. I got my idea because, in effect, I’d been a virtual PA all along. My boss was usually only in the office a couple of days a month, so we’d always worked remotely by email and phone calls. I thought I could offer a similar service to other busy people. Now I’ve got all sorts of regular clients, including surveyors, solicitors, an advertising agency and even an author. I never expected such a mix. I can’t wait to see what challenges lie in store for me.

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43-a 44-b 45-c 46-d 47-c 48-a 49-c 50-d 51-b 52-a

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You are going to read an extract from a novel. For questions 31-36, choose the answer (A, B, C or 0) which you think fits best according to the text. Trip to Scotland The four of us, my best friend Ruth, my parents and me, were walking over a piece of damp moorland in Scotland. It was cold, in spite of the spring sunshine, and rather bleak. I have to say, I’d been quite anxious about Ruth when we set out. I wasn’t sure how a New Yorker would react to all this empty scenery. Although she’s lived in London for years, this was the first time she’d ever been to Scotland, which was surprising. It was also the first time she’d been on a trip with my family, which was not so surprising. My parents almost never go away. My family runs a travel agency, so a holiday’s just like work for them – or so they say. Just occasionally, though, something gets them moving. This time it was a small advert in the newspaper. My father saw it in the travel section, which normally he only reads for research purposes. It was a special offer – a long weekend in a farmhouse at a really good price. What was crucial, though, was that it ended with the magic words ‘excellent bird-watching country’. Suddenly, we were in the car heading north for Scotland. ‘I think I’ve just seen a sparrow-harrier,’ said Ruth, ‘but now all I’m getting is sky.’ ‘Binoculars can be very tricky if you’re not used to them,’ said my mother. ‘So can bird names,’ I said. ‘You’ve just invented the sparrow-harrier. It must’ve been either a sparrowhawk or a hen harrier. My father was struggling with one foot deep in a wet patch of mud. He heaved it free; it gave (LINE 18) out a loud squelch. ‘In actual fact,’ he said, ‘it was a buzzard.’ I think Dad likes bird-watching the way some people like fishing. It gives him an excuse to go somewhere lonely and stare into space. To be fair, though, he can get quite animated; when he thought he’d spotted a firecrest up an oak tree, he brought the binoculars up so fast he blacked both his eyes. I remember trying not to laugh. Somehow, though, I hadn’t expected Ruth to find it appealing. Here she was staring at a disappearing dot in the sky and saying, ‘Okay. So can I claim to have seen a buzzard? Even though I didn’t know what it was?’ My father bent down and pointed to a small, boring plant, half-hidden in the grass. ‘What’s that?’ he said. Ruth examined it carefully. ‘I have absolutely no idea,’ she said. ‘Neither have I,’ said my father, ‘but whatever it is, we’ve definitely both seen it.’ ‘I think that was a “yes” to your buzzard question,’ said my mother. We only had one more day away. Then it was back to reality for all of us. Ruth and I are both taking a ‘year out’ between school and college. I have to admit things weren’t turning out exactly as we expected – though bits have been really good. The idea was to work and save, then travel and party. I got a job at once, as an assistant at the agency. I would like to point out, here, that this only sounds like an easy option to people who have never worked for my parents. It’s been hard for Ruth to find jobs though, so she never has much money. It’s a pity because, wherever you want to travel, you have to pay – unless you’re my parents, of course. It was on the walk back to the farm that they began to discuss all the free holidays they’d had over the years. Which I have to say I thought was very tactless of them.

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31 What worried the narrator about the trip before they left? C whether Ruth would appreciate the landscape. B whether her parents would enjoy themselves. A whether Ruth would get on with her parents. D whether low temperatures would spoil their fun

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32 According to the narrator, what had attracted her father to the trip C the chance to practise his hobby. D the opportunities for research. B the relatively low cost it involved. A the place where he saw it advertised

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33 The word ‘squelch’ in line 18 describes A the noise something made.. B the way something looked.. D a way of talking about something.. c a way of moving something.

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34 The narrator mentions the incident with the firecrest to show D how knowledgeable about birds her father was.. A how unlucky her father tended to be.. C how amusing her father could be at times.. B how keen on bird-watching her father was.

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35 How does the narrator feel about her ‘year out’ so far? D This holiday is the best part of it to date.. B She is thoroughly disappointed by it.. C It has not been going according to plan.. A Most of it has been enjoyable.

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36 What does the narrator suggest about her job? A It isn’t very well paid.. D It’s much harder than people imagine.. B It doesn’t really interest her.. c It’s fun working with her parents.

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31-c 32-c 33-a 34-b 35-c 36-d

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Reading Прочитайте тексты и установите соответствие между текстами и их заголовками: к каждому тексту, обозначенному буквами А–G, подберите соответствующий заголовок, обозначенный цифрами 1–8. Используйте каждую цифру только один раз. В задании есть один лишний заголовок. 1. One product — many dishes 2. Simple to prepare 3. Once local — now global 4. Good for everyone 5. More than food 6. Impossible to grow 7. Synonymous to food 8. Differrent table manners

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A. Over the centuries, rice has become a part of the traditions of many cultures. In some societies, it is traditional to throw a handful of rice on newlywed couples, symbolizing the wish for a large family and prosperity. In India, rice is traditionally the first food that bride offers her new husband. It is typical for people to leave offerings of rice in Buddhist temples. In Thailand, the annual Royal Plowing Ceremony has taken place in front of the Grand Palace in Bangkok for seven centuries. B. The basic recipe for cooking rice is easy. First you need to bring 2 cups of water to boil. When the water is boiling, add 1 cup of rice. Cover the pot. As soon as the water boils again, reduce the heat. Let the rice cook for 15 to 20 minutes. The rice is ready when all the water is absorbed. It’s now possible to buy rice cooking machines that cook perfect rice every time, especially in large quantities. This is particularly helpful in Asian cultures, where families often eat rice with every meal. In these countries, rice is also used to make pancakes, sweets and wine — indeed almost anything! C. Rice is the primary source of nutrition for more than half of the world’s population. Countries as different as Japan, India, Nigeria and Mexico use rice in their national cuisine. In Chinese, the word for rice is the same as the word for food. And in Thailand, when you call your family to a meal, you say “eat rice.” So it’s easy to understand why the 2008 global rice shortage was a real crisis for billions of people. In some countries the shortage led to big price increases. Some governments had to control the sale of rice. D. Many people consider rice to be one of the healthiest of possible food choices. It has no sodium or cholesterol, and almost no fat. One half cup of rice has approximately 100 calories, and those calories are rich in important vitamins and minerals, including folic acid, iron and zinc. Many athletes eat rice because as a carbohydrate it is a great source of energy. Rice even has certain chemicals in it that are supposed to improve your mood. Brown rice is the healthiest of all because it is 100% grain. E. Archeologists believe that rice has been grown as a source of food for at least 4000 years. It was first grown in China, and then introduced to India. Over the centuries the practice of growing rice has spread literally across the globe. Today rice is grown in Peru, Egypt, and even the United States, but over 90% of the world’s rice is still grown in Asian countries. Rice is best grown in wet, sub-tropical climates, and in many countries it is still cultivated using intensive human and animal labor. For this reason, large families are still typical, and the water buffalo is a valued possession. F. One of the amazing things about rice is how adaptable it is. It is an essential ingredient in cuisines all around the world — cuisines as different as Japanese, Mexican, and West African. The Japanese combine sticky rice with raw fish to create numerous varieties of sushi. Mexican rice, flavored with cumin and tomatoes, is a colorful side dish. Every country in West Africa has its own version of a regional rice dish called jollof , often served with fried plantain, a kind of banana. G. All around the world people eat rice in different ways. In India it is traditional to eat rice with your right hand. You just mix the rice with a little curry, roll it into a ball, and pop it into your mouth. In China it’s common to use chopsticks (or kuaizi ). People in Korea, Thailand and Vietnam eat their rice with a spoon. And in European countries and in the United States rice is eaten with a fork.

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1. One product — many dishes — 5 2. Simple to prepare -2 3. Once local — now global -7 4. Good for everyone- 4 5. More than food- 3 6. Impossible to grow — 7. Synonymous to food -1 8. Differrent table manners-8

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A — 5 «Over the centuries, rice has become a part of the traditions of many cultures» B — 2 «The basic recipe for cooking rice is easy. » C — 7 » In Chinese, the word for rice is the same as the word for food. And in Thailand, when you call your family to a meal, you say “eat rice.” D — 4 «Many people consider rice to be one of the healthiest of possible food choices. » E — 3 «Over the centuries the practice of growing rice has spread literally across the globe.» F — 1 » It is an essential ingredient in cuisines all around the world — cuisines as different as Japanese, Mexican, and West African. » G — 8 » All around the world people eat rice in different ways. «

Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of the molten form; some glasses such as volcanic glass are naturally occurring. The most familiar, and historically the oldest, types of manufactured glass are «silicate glasses» based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. Soda–lime glass, containing around 70% silica, accounts for around 90% of manufactured glass. The term glass, in popular usage, is often used to refer only to this type of material, although silica-free glasses often have desirable properties for applications in modern communications technology. Some objects, such as drinking glasses and eyeglasses, are so commonly made of silicate-based glass that they are simply called by the name of the material.

Despite being brittle, buried silicate glass will survive for very long periods if not disturbed, and many examples of glass fragments exist from early glass-making cultures. Archaeological evidence suggests glass-making dates back to at least 3,600 BC in Mesopotamia, Egypt, or Syria. The earliest known glass objects were beads, perhaps created accidentally during metalworking or the production of faience. Due to its ease of formability into any shape, glass has been traditionally used for vessels, such as bowls, vases, bottles, jars and drinking glasses. In its most solid forms, it has also been used for paperweights and marbles. Glass can be coloured by adding metal salts or painted and printed as enamelled glass. The refractive, reflective and transmission properties of glass make glass suitable for manufacturing optical lenses, prisms, and optoelectronics materials. Extruded glass fibres have application as optical fibres in communications networks, thermal insulating material when matted as glass wool so as to trap air, or in glass-fibre reinforced plastic (fibreglass).

Microscopic structure

The standard definition of a glass (or vitreous solid) is a solid formed by rapid melt quenching.^[1][2][3][4] However, the term «glass» is often defined in a broader sense, to describe any non-crystalline (amorphous) solid that exhibits a glass transition when heated towards the liquid state.^[4][5]

Glass is an amorphous solid. Although the atomic-scale structure of glass shares characteristics of the structure of a supercooled liquid, glass exhibits all the mechanical properties of a solid.^[6][7][8] As in other amorphous solids, the atomic structure of a glass lacks the long-range periodicity observed in crystalline solids. Due to chemical bonding constraints, glasses do possess a high degree of short-range order with respect to local atomic polyhedra.^[9] The notion that glass flows to an appreciable extent over extended periods of time is not supported by empirical research or theoretical analysis (see viscosity in solids). Though a material viscosity on the order of 10¹⁷–10¹⁸ Pa s can be measured in glass, such a high value reinforces the fact that glass would not change shape appreciably over even large periods of time.^[5][10]

Formation from a supercooled liquid

For melt quenching, if the cooling is sufficiently rapid (relative to the characteristic crystallization time) then crystallization is prevented and instead the disordered atomic configuration of the supercooled liquid is frozen into the solid state at T_g. The tendency for a material to form a glass while quenched is called glass-forming ability. This ability can be predicted by the rigidity theory.^[12] Generally, a glass exists in a structurally metastable state with respect to its crystalline form, although in certain circumstances, for example in atactic polymers, there is no crystalline analogue of the amorphous phase.^[13]

Glass is sometimes considered to be a liquid due to its lack of a first-order phase transition^[7][14]
where certain thermodynamic variables such as volume, entropy and enthalpy are discontinuous through the glass transition range. The glass transition may be described as analogous to a second-order phase transition where the intensive thermodynamic variables such as the thermal expansivity and heat capacity are discontinuous, however this is incorrect.^[2] The equilibrium theory of phase transformations do not hold for glass, and hence the glass transition cannot be classed as one of the classical equilibrium phase transformations in solids.^[4][5] Furthermore, it does not describe the temperature dependence of Tg upon heating rate, as found in differential scanning calorimetry.

Occurrence in nature

Glass can form naturally from volcanic magma. Obsidian is a common volcanic glass with high silica (SiO₂) content formed when felsic lava extruded from a volcano cools rapidly.^[15] Impactite is a form of glass formed by the impact of a meteorite, where Moldavite (found in central and eastern Europe), and Libyan desert glass (found in areas in the eastern Sahara, the deserts of eastern Libya and western Egypt) are notable examples.^[16] Vitrification of quartz can also occur when lightning strikes sand, forming hollow, branching rootlike structures called fulgurites.^[17] Trinitite is a glassy residue formed from the desert floor sand at the Trinity nuclear bomb test site.^[18] Edeowie glass, found in South Australia, is proposed to originate from Pleistocene grassland fires, lightning strikes, or hypervelocity impact by one or several asteroids or comets.^[19]

History

Naturally occurring obsidian glass was used by Stone Age societies as it fractures along very sharp edges, making it ideal for cutting tools and weapons.^[20][21] Glassmaking dates back at least 6000 years, long before humans had discovered how to smelt iron.^[20] Archaeological evidence suggests that the first true synthetic glass was made in Lebanon and the coastal north Syria, Mesopotamia or ancient Egypt.^[22][23] The earliest known glass objects, of the mid-third millennium BC, were beads, perhaps initially created as accidental by-products of metalworking (slags) or during the production of faience, a pre-glass vitreous material made by a process similar to glazing.^[24]
Early glass was rarely transparent and often contained impurities and imperfections,^[20] and is technically faience rather than true glass, which did not appear until the 15th century BC.^[25] However, red-orange glass beads excavated from the Indus Valley Civilization dated before 1700 BC (possibly as early as 1900 BC) predate sustained glass production, which appeared around 1600 BC in Mesopotamia and 1500 BC in Egypt.^[26][27] During the Late Bronze Age there was a rapid growth in glassmaking technology in Egypt and Western Asia.^[22] Archaeological finds from this period include coloured glass ingots, vessels, and beads.^[22][28] Much early glass production relied on grinding techniques borrowed from stoneworking, such as grinding and carving glass in a cold state.^[29]

The term glass developed in the late Roman Empire. It was in the Roman glassmaking centre at Trier (located in current-day Germany) that the late-Latin term glesum originated, probably from a Germanic word for a transparent, lustrous substance.^[30] Glass objects have been recovered across the Roman Empire^[31] in domestic, funerary,^[32] and industrial contexts,^[33] as well as trade items in marketplaces in distant provinces.^[34][35] Examples of Roman glass have been found outside of the former Roman Empire in China,^[36] the Baltics, the Middle East, and India.^[37] The Romans perfected cameo glass, produced by etching and carving through fused layers of different colours to produce a design in relief on the glass object.^[38]

In post-classical West Africa, Benin was a manufacturer of glass and glass beads.^[39]
Glass was used extensively in Europe during the Middle Ages. Anglo-Saxon glass has been found across England during archaeological excavations of both settlement and cemetery sites.^[40] From the 10th century onwards, glass was employed in stained glass windows of churches and cathedrals, with famous examples at Chartres Cathedral and the Basilica of Saint-Denis. By the 14th century, architects were designing buildings with walls of stained glass such as Sainte-Chapelle, Paris, (1203–1248) and the East end of Gloucester Cathedral. With the change in architectural style during the Renaissance period in Europe, the use of large stained glass windows became much less prevalent,^[41] although stained glass had a major revival with Gothic Revival architecture in the 19th century.^[42]

During the 13th century, the island of Murano, Venice, became a centre for glass making, building on medieval techniques to produce colourful ornamental pieces in large quantities.^[38] Murano glass makers developed the exceptionally clear colourless glass cristallo, so called for its resemblance to natural crystal, which was extensively used for windows, mirrors, ships’ lanterns, and lenses.^[20] In the 13th, 14th, and 15th centuries, enamelling and gilding on glass vessels was perfected in Egypt and Syria.^[43] Towards the end of the 17th century, Bohemia became an important region for glass production, remaining so until the start of the 20th century. By the 17th century, glass in the Venetian tradition was also being produced in England. In about 1675, George Ravenscroft invented lead crystal glass, with cut glass becoming fashionable in the 18th century.^[38] Ornamental glass objects became an important art medium during the Art Nouveau period in the late 19th century.^[38]

Throughout the 20th century, new mass production techniques led to widespread availability of glass in much larger amounts, making it practical as a building material and enabling new applications of glass.^[44] In the 1920s a mould-etch process was developed, in which art was etched directly into the mould, so that each cast piece emerged from the mould with the image already on the surface of the glass. This reduced manufacturing costs and, combined with a wider use of coloured glass, led to cheap glassware in the 1930s, which later became known as Depression glass.^[45] In the 1950s, Pilkington Bros., England, developed the float glass process, producing high-quality distortion-free flat sheets of glass by floating on molten tin.^[20] Modern multi-story buildings are frequently constructed with curtain walls made almost entirely of glass.^[46] Laminated glass has been widely applied to vehicles for windscreens.^[47] Optical glass for spectacles has been used since the Middle Ages.^[48] The production of lenses has become increasingly proficient, aiding astronomers^[49] as well as having other application in medicine and science.^[50] Glass is also employed as the aperture cover in many solar energy collectors.^[51]

In the 21st century, glass manufacturers have developed different brands of chemically strengthened glass for widespread application in touchscreens for smartphones, tablet computers, and many other types of information appliances. These include Gorilla Glass, developed and manufactured by Corning, AGC Inc.’s Dragontrail and Schott AG’s Xensation.^[52][53][54]

Physical properties

Optical

Glass is in widespread use in optical systems due to its ability to refract, reflect, and transmit light following geometrical optics. The most common and oldest applications of glass in optics are as lenses, windows, mirrors, and prisms.^[55] The key optical properties refractive index, dispersion, and transmission, of glass are strongly dependent on chemical composition and, to a lesser degree, its thermal history.^[55] Optical glass typically has a refractive index of 1.4 to 2.4, and an Abbe number (which characterises dispersion) of 15 to 100.^[55] Refractive index may be modified by high-density (refractive index increases) or low-density (refractive index decreases) additives.^[56]

Glass transparency results from the absence of grain boundaries which diffusely scatter light in polycrystalline materials.^[57] Semi-opacity due to crystallization may be induced in many glasses by maintaining them for a long period at a temperature just insufficient to cause fusion. In this way, the crystalline, devitrified material, known as Réaumur’s glass porcelain is produced.^[43][58] Although generally transparent to visible light, glasses may be opaque to other wavelengths of light. While silicate glasses are generally opaque to infrared wavelengths with a transmission cut-off at 4 μm, heavy-metal fluoride and chalcogenide glasses are transparent to infrared wavelengths of up to 7 and up to 18 μm, respectively.^[59] The addition of metallic oxides results in different coloured glasses as the metallic ions will absorb wavelengths of light corresponding to specific colours.^[59]

Other

In the manufacturing process, glasses can be poured, formed, extruded and molded into forms ranging from flat sheets to highly intricate shapes.^[60] The finished product is brittle and will fracture, unless laminated or tempered to enhance durability.^[61][62] Glass is typically inert, resistant to chemical attack, and can mostly withstand the action of water, making it an ideal material for the manufacture of containers for foodstuffs and most chemicals.^[20][63][64] Nevertheless, although usually highly resistant to chemical attack, glass will corrode or dissolve under some conditions.^[63][65] The materials that make up a particular glass composition have an effect on how quickly the glass corrodes. Glasses containing a high proportion of alkali or alkaline earth elements are more susceptible to corrosion than other glass compositions.^[66][67]

The density of glass varies with chemical composition with values ranging from 2.2 grams per cubic centimetre (2,200 kg/m³) for fused silica to 7.2 grams per cubic centimetre (7,200 kg/m³) for dense flint glass.^[68] Glass is stronger than most metals, with a theoretical tensile strength for pure, flawless glass estimated at 14 to 35 gigapascals (2,000,000 to 5,100,000 psi) due to its ability to undergo reversible compression without fracture. However, the presence of scratches, bubbles, and other microscopic flaws lead to a typical range of 14 to 175 megapascals (2,000 to 25,400 psi) in most commercial glasses.^[59] Several processes such as toughening can increase the strength of glass.^[69] Carefully drawn flawless glass fibres can be produced with strength of up to 11.5 gigapascals (1,670,000 psi).^[59]

Reputed flow

The observation that old windows are sometimes found to be thicker at the bottom than at the top is often offered as supporting evidence for the view that glass flows over a timescale of centuries, the assumption being that the glass has exhibited the liquid property of flowing from one shape to another.^[70] This assumption is incorrect, as once solidified, glass stops flowing. The sags and ripples observed in old glass were already there the day it was made; manufacturing processes used in the past produced sheets with imperfect surfaces and non-uniform thickness.^[7] (The near-perfect float glass used today only became widespread in the 1960s.)

The rate of glass flow in mediaeval windows was calculated in 2017. It was found that the glass was 16 orders of magnitude (10¹⁶ times) less viscous (hence freer-flowing) than expected at room temperature—16 orders of magnitude less than previous estimates based on soda–lime–silicate glass. It was estimated that the rate of flow would not exceed 1nm per billion years.^[71][72]

Types

Silicate

Silicon dioxide (SiO₂) is a common fundamental constituent of glass. Fused quartz is a glass made from chemically pure silica.^[67] It has very low thermal expansion and excellent resistance to thermal shock, being able to survive immersion in water while red hot, resists high temperatures (1000–1500 °C) and chemical weathering, and is very hard. It is also transparent to a wider spectral range than ordinary glass, extending from the visible further into both the UV and IR ranges, and is sometimes used where transparency to these wavelengths is necessary. Fused quartz is used for high-temperature applications such as furnace tubes, lighting tubes, melting crucibles, etc.^[73] However, its high melting temperature (1723 °C) and viscosity make it difficult to work with. Therefore, normally, other substances (fluxes) are added to lower the melting temperature and simplify glass processing.^[74]

Soda–lime

Sodium carbonate (Na₂CO₃, «soda») is a common additive and acts to lower the glass-transition temperature. However, sodium silicate is water-soluble, so lime (CaO, calcium oxide, generally obtained from limestone), along with magnesium oxide (MgO), and aluminium oxide (Al₂O₃), are commonly added to improve chemical durability. Soda–lime glasses (Na₂O) + lime (CaO) + magnesia (MgO) + alumina (Al₂O₃) account for over 75% of manufactured glass, containing about 70 to 74% silica by weight.^[67][75] Soda–lime–silicate glass is transparent, easily formed, and most suitable for window glass and tableware.^[76] However, it has a high thermal expansion and poor resistance to heat.^[76] Soda–lime glass is typically used for windows, bottles, light bulbs, and jars.^[74]

Borosilicate

Borosilicate glasses (e.g. Pyrex, Duran) typically contain 5–13% boron trioxide (B₂O₃).^[74] Borosilicate glasses have fairly low coefficients of thermal expansion (7740 Pyrex CTE is 3.25×10⁻⁶/°C^[77] as compared to about 9×10⁻⁶/°C for a typical soda–lime glass^[78]). They are, therefore, less subject to stress caused by thermal expansion and thus less vulnerable to cracking from thermal shock. They are commonly used for e.g. labware, household cookware, and sealed beam car head lamps.^[74]

Lead

The addition of lead(II) oxide into silicate glass lowers melting point and viscosity of the melt.^[79] The high density of lead glass (silica + lead oxide (PbO) + potassium oxide (K₂O) + soda (Na₂O) + zinc oxide (ZnO) + alumina) results in a high electron density, and hence high refractive index, making the look of glassware more brilliant and causing noticeably more specular reflection and increased optical dispersion.^[67][80] Lead glass has a high elasticity, making the glassware more workable and giving rise to a clear «ring» sound when struck. However, lead glass cannot withstand high temperatures well.^[73] Lead oxide also facilitates solubility of other metal oxides and is used in colored glass. The viscosity decrease of lead glass melt is very significant (roughly 100 times in comparison with soda glass); this allows easier removal of bubbles and working at lower temperatures, hence its frequent use as an additive in vitreous enamels and glass solders. The high ionic radius of the Pb²⁺ ion renders it highly immobile and hinders the movement of other ions; lead glasses therefore have high electrical resistance, about two orders of magnitude higher than soda–lime glass (10^8.5 vs 10^6.5 Ω⋅cm, DC at 250 °C).^[81]

Aluminosilicate

Aluminosilicate glass typically contains 5–10% alumina (Al₂O₃). Aluminosilicate glass tends to be more difficult to melt and shape compared to borosilicate compositions, but has excellent thermal resistance and durability.^[74] Aluminosilicate glass is extensively used for fiberglass,^[82] used for making glass-reinforced plastics (boats, fishing rods, etc.), top-of-stove cookware, and halogen bulb glass.^[73][74]

Other oxide additives

The addition of barium also increases the refractive index. Thorium oxide gives glass a high refractive index and low dispersion and was formerly used in producing high-quality lenses, but due to its radioactivity has been replaced by lanthanum oxide in modern eyeglasses.^[83] Iron can be incorporated into glass to absorb infrared radiation, for example in heat-absorbing filters for movie projectors, while cerium(IV) oxide can be used for glass that absorbs ultraviolet wavelengths.^[84] Fluorine lowers the dielectric constant of glass. Fluorine is highly electronegative and lowers the polarizability of the material. Fluoride silicate glasses are used in manufacture of integrated circuits as an insulator.^[85]

Glass-ceramics

Glass-ceramic materials contain both non-crystalline glass and crystalline ceramic phases. They are formed by controlled nucleation and partial crystallisation of a base glass by heat treatment.^[86] Crystalline grains are often embedded within a non-crystalline intergranular phase of grain boundaries. Glass-ceramics exhibit advantageous thermal, chemical, biological, and dielectric properties as compared to metals or organic polymers.^[86]

The most commercially important property of glass-ceramics is their imperviousness to thermal shock. Thus, glass-ceramics have become extremely useful for countertop cooking and industrial processes. The negative thermal expansion coefficient (CTE) of the crystalline ceramic phase can be balanced with the positive CTE of the glassy phase. At a certain point (~70% crystalline) the glass-ceramic has a net CTE near zero. This type of glass-ceramic exhibits excellent mechanical properties and can sustain repeated and quick temperature changes up to 1000 °C.^[87][86]

Fibreglass

Fibreglass (also called glass fibre reinforced plastic, GRP) is a composite material made by reinforcing a plastic resin with glass fibres. It is made by melting glass and stretching the glass into fibres. These fibres are woven together into a cloth and left to set in a plastic resin.^[88][89][90]
Fibreglass has the properties of being lightweight and corrosion resistant, and is a good insulator enabling its use as building insulation material and for electronic housing for consumer products. Fibreglass was originally used in the United Kingdom and United States during World War II to manufacture radomes. Uses of fibreglass include building and construction materials, boat hulls, car body parts, and aerospace composite materials.^[91][88][90]

Glass-fibre wool is an excellent thermal and sound insulation material, commonly used in buildings (e.g. attic and cavity wall insulation), and plumbing (e.g. pipe insulation), and soundproofing.^[91] It is produced by forcing molten glass through a fine mesh by centripetal force, and breaking the extruded glass fibres into short lengths using a stream of high-velocity air. The fibres are bonded with an adhesive spray and the resulting wool mat is cut and packed in rolls or panels.^[59]

Non-silicate

Besides common silica-based glasses many other inorganic and organic materials may also form glasses, including metals, aluminates, phosphates, borates, chalcogenides, fluorides, germanates (glasses based on GeO₂), tellurites (glasses based on TeO₂), antimonates (glasses based on Sb₂O₃), arsenates (glasses based on As₂O₃), titanates (glasses based on TiO₂), tantalates (glasses based on Ta₂O₅), nitrates, carbonates, plastics, acrylic, and many other substances.^[5] Some of these glasses (e.g. Germanium dioxide (GeO₂, Germania), in many respects a structural analogue of silica, fluoride, aluminate, phosphate, borate, and chalcogenide glasses) have physico-chemical properties useful for their application in fibre-optic waveguides in communication networks and other specialized technological applications.^[93][94]

Silica-free glasses may often have poor glass forming tendencies. Novel techniques, including containerless processing by aerodynamic levitation (cooling the melt whilst it floats on a gas stream) or splat quenching (pressing the melt between two metal anvils or rollers), may be used increase cooling rate, or reduce crystal nucleation triggers.^[95][96][97]

Amorphous metals

In the past, small batches of amorphous metals with high surface area configurations (ribbons, wires, films, etc.) have been produced through the implementation of extremely rapid rates of cooling. Amorphous metal wires have been produced by sputtering molten metal onto a spinning metal disk.^[98][99]

A number of alloys have been produced in layers with thickness exceeding 1 millimeter. These are known as bulk metallic glasses (BMG). Liquidmetal Technologies sell a number of zirconium-based BMGs.

Batches of amorphous steel have also been produced that demonstrate mechanical properties far exceeding those found in conventional steel alloys.^[100]

Experimental evidence indicates that the system Al-Fe-Si may undergo a first-order transition to an amorphous form (dubbed «q-glass») on rapid cooling from the melt. Transmission electron microscopy (TEM) images indicate that q-glass nucleates from the melt as discrete particles with a uniform spherical growth in all directions. While x-ray diffraction reveals the isotropic nature of q-glass, a nucleation barrier exists implying an interfacial discontinuity (or internal surface) between the glass and melt phases.^[101][102]

Polymers

Important polymer glasses include amorphous and glassy pharmaceutical compounds. These are useful because the solubility of the compound is greatly increased when it is amorphous compared to the same crystalline composition. Many emerging pharmaceuticals are practically insoluble in their crystalline forms.^[103] Many polymer thermoplastics familiar from everyday use are glasses. For many applications, like glass bottles or eyewear, polymer glasses (acrylic glass, polycarbonate or polyethylene terephthalate) are a lighter alternative to traditional glass.^[104]

Molecular liquids and molten salts

Molecular liquids, electrolytes, molten salts, and aqueous solutions are mixtures of different molecules or ions that do not form a covalent network but interact only through weak van der Waals forces or through transient hydrogen bonds. In a mixture of three or more ionic species of dissimilar size and shape, crystallization can be so difficult that the liquid can easily be supercooled into a glass.^[105][106] Examples include LiCl:RH₂O (a solution of lithium chloride salt and water molecules) in the composition range 4<R<8.^[107] sugar glass,^[108] or Ca_0.4K_0.6(NO₃)_1.4.^[109] Glass electrolytes in the form of Ba-doped Li-glass and Ba-doped Na-glass have been proposed as solutions to problems identified with organic liquid electrolytes used in modern lithium-ion battery cells.^[110]

Production

Following the glass batch preparation and mixing, the raw materials are transported to the furnace. Soda–lime glass for mass production is melted in glass melting furnaces. Smaller scale furnaces for specialty glasses include electric melters, pot furnaces, and day tanks.^[75]
After melting, homogenization and refining (removal of bubbles), the glass is formed. Flat glass for windows and similar applications is formed by the float glass process, developed between 1953 and 1957 by Sir Alastair Pilkington and Kenneth Bickerstaff of the UK’s Pilkington Brothers, who created a continuous ribbon of glass using a molten tin bath on which the molten glass flows unhindered under the influence of gravity. The top surface of the glass is subjected to nitrogen under pressure to obtain a polished finish.^[111] Container glass for common bottles and jars is formed by blowing and pressing methods.^[112] This glass is often slightly modified chemically (with more alumina and calcium oxide) for greater water resistance.^[113]

Once the desired form is obtained, glass is usually annealed for the removal of stresses and to increase the glass’s hardness and durability.^[114] Surface treatments, coatings or lamination may follow to improve the chemical durability (glass container coatings, glass container internal treatment), strength (toughened glass, bulletproof glass, windshields^[115]), or optical properties (insulated glazing, anti-reflective coating).^[116]

New chemical glass compositions or new treatment techniques can be initially investigated in small-scale laboratory experiments. The raw materials for laboratory-scale glass melts are often different from those used in mass production because the cost factor has a low priority. In the laboratory mostly pure chemicals are used. Care must be taken that the raw materials have not reacted with moisture or other chemicals in the environment (such as alkali or alkaline earth metal oxides and hydroxides, or boron oxide), or that the impurities are quantified (loss on ignition).^[117] Evaporation losses during glass melting should be considered during the selection of the raw materials, e.g., sodium selenite may be preferred over easily evaporating selenium dioxide (SeO₂). Also, more readily reacting raw materials may be preferred over relatively inert ones, such as aluminum hydroxide (Al(OH)₃) over alumina (Al₂O₃). Usually, the melts are carried out in platinum crucibles to reduce contamination from the crucible material. Glass homogeneity is achieved by homogenizing the raw materials mixture (glass batch), by stirring the melt, and by crushing and re-melting the first melt. The obtained glass is usually annealed to prevent breakage during processing.^[117][118]

Colour

Colour in glass may be obtained by addition of homogenously distributed electrically charged ions (or colour centres). While ordinary soda–lime glass appears colourless in thin section, iron(II) oxide (FeO) impurities produce a green tint in thick sections.^[119] Manganese dioxide (MnO₂), which gives glass a purple colour, may be added to remove the green tint given by FeO.^[120] FeO and chromium(III) oxide (Cr₂O₃) additives are used in the production of green bottles.^[119] Iron (III) oxide, on the other-hand, produces yellow or yellow-brown glass.^[121] Low concentrations (0.025 to 0.1%) of cobalt oxide (CoO) produces rich, deep blue cobalt glass.^[122] Chromium is a very powerful colourising agent, yielding dark green.^[123]
Sulphur combined with carbon and iron salts produces amber glass ranging from yellowish to almost black.^[124] A glass melt can also acquire an amber colour from a reducing combustion atmosphere.^[125] Cadmium sulfide produces imperial red, and combined with selenium can produce shades of yellow, orange, and red.^[119][121] The additive Copper(II) oxide (CuO) produces a turquoise colour in glass, in contrast to Copper(I) oxide (Cu₂O) which gives a dull brown-red colour.^[126]

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  Red glass bottle with yellow glass overlay

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  Amber-coloured glass

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  Four-colour Roman glass bowl, manufactured circa 1st century B.C.

Uses

Architecture and windows

Soda–lime sheet glass is typically used as transparent glazing material, typically as windows in external walls of buildings. Float or rolled sheet glass products is cut to size either by scoring and snapping the material, laser cutting, water jets, or diamond bladed saw. The glass may be thermally or chemically tempered (strengthened) for safety and bent or curved during heating. Surface coatings may be added for specific functions such as scratch resistance, blocking specific wavelengths of light (e.g. infrared or ultraviolet), dirt-repellence (e.g. self-cleaning glass), or switchable electrochromic coatings.^[127]

Structural glazing systems represent one of the most significant architectural innovations of modern times, where glass buildings now often dominate skylines of many modern cities.^[128] These systems use stainless steel fittings countersunk into recesses in the corners of the glass panels allowing strengthened panes to appear unsupported creating a flush exterior.^[128] Structural glazing systems have their roots in iron and glass conservatories of the nineteenth century^[129]

Tableware

Glass is an essential component of tableware and is typically used for water, beer and wine drinking glasses.^[50] Wine glasses are typically stemware, i.e. goblets formed from a bowl, stem, and foot. Crystal or Lead crystal glass may be cut and polished to produce decorative drinking glasses with gleaming facets.^[130][131] Other uses of glass in tableware include decanters, jugs, plates, and bowls.^[50]

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  Wine glasses and other glass tableware

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  Dimpled glass beer pint jug

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Packaging

The inert and impermeable nature of glass makes it a stable and widely used material for food and drink packaging as glass bottles and jars. Most container glass is soda–lime glass, produced by blowing and pressing techniques. Container glass has a lower magnesium oxide and sodium oxide content than flat glass, and a higher silica, calcium oxide, and aluminum oxide content.^[132] Its higher content of water-insoluble oxides imparts slightly higher chemical durability against water, which is advantageous for storing beverages and food. Glass packaging is sustainable, readily recycled, reusable and refillable.^[133]

For electronics applications, glass can be used as a substrate in the manufacture of integrated passive devices, thin-film bulk acoustic resonators, and as a hermetic sealing material in device packaging,^[134][135] including very thin solely glass based encapsulation of integrated circuits and other semiconductors in high manufacturing volumes.^[136]

Laboratories

Glass is an important material in scientific laboratories for the manufacture of experimental apparatus because it is relatively cheap, readily formed into required shapes for experiment, easy to keep clean, can withstand heat and cold treatment, is generally non-reactive with many reagents, and its transparency allows for the observation of chemical reactions and processes.^[137][138] Laboratory glassware applications include flasks, petri dishes, test tubes, pipettes, graduated cylinders, glass lined metallic containers for chemical processing, fractionation columns, glass pipes, Schlenk lines, gauges, and thermometers.^[139][137] Although most standard laboratory glassware has been mass-produced since the 1920s, scientists still employ skilled glassblowers to manufacture bespoke glass apparatus for their experimental requirements.^[140]

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  A Vigreux column in a laboratory setup

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Optics

Glass is a ubiquitous material in optics by virtue of its ability to refract, reflect, and transmit light. These and other optical properties can be controlled by varying chemical compositions, thermal treatment, and manufacturing techniques. The many applications of glass in optics includes glasses for eyesight correction, imaging optics (e.g. lenses and mirrors in telescopes, microscopes, and cameras), fibre optics in telecommunications technology, and integrated optics. Microlenses and gradient-index optics (where the refractive index is non-uniform) find application in e.g. reading optical discs, laser printers, photocopiers, and laser diodes.^[55]

Art

Glass as art dates to least 1300 BC shown as an example of natural glass found in Tutankhamun’s pectoral,^[141] which also contained vitreous enamel, that is to say, melted coloured glass used on a metal backing. Enamelled glass, the decoration of glass vessels with coloured glass paints, has existed since 1300 BC,^[142] and was prominent in the early 20th century with Art Nouveau glass and that of the House of Fabergé in St. Petersburg, Russia. Both techniques were used in stained glass, which reached its height roughly from 1000 to 1550, before a revival in the 19th century.

The 19th century saw a revival in ancient glass-making techniques including cameo glass, achieved for the first time since the Roman Empire, initially mostly for pieces in a neo-classical style. The Art Nouveau movement made great use of glass, with René Lalique, Émile Gallé, and Daum of Nancy in the first French wave of the movement, producing coloured vases and similar pieces, often in cameo glass or in lustre glass techniques.^[143]

Louis Comfort Tiffany in America specialized in stained glass, both secular and religious, in panels and his famous lamps. The early 20th-century saw the large-scale factory production of glass art by firms such as Waterford and Lalique. Small studios may hand-produce glass artworks. Techniques for producing glass art include blowing, kiln-casting, fusing, slumping, pâte de verre, flame-working, hot-sculpting and cold-working. Cold work includes traditional stained glass work and other methods of shaping glass at room temperature. Objects made out of glass include vessels, paperweights, marbles, beads, sculptures and installation art.^[144]

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  Émile Gallé, Marquetry glass vase with clematis flowers (1890-1900)

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  A glass sculpture by Dale Chihuly, «The Sun» at the «Gardens of Glass» exhibition in Kew Gardens, London

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  Modern stained glass window

See also

References

External links

• «Glass» . Encyclopædia Britannica. Vol. 12 (11th ed.). 1911.
• The Story of Glass Making in Canada from The Canadian Museum of Civilization.
• «How Your Glass Ware Is Made» by George W. Waltz, February 1951, Popular Science.
• All About Glass from the Corning Museum of Glass: a collection of articles, multimedia, and virtual books all about glass, including the Glass Dictionary.
• National Glass Association—The largest trade association representing the flat (architectural), auto glass, and window & door industries