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We all know that everything around us consists of atoms of particular elements. As elements were discovered and named, it became necessary to develop a system to organize all the elements. The system we know today as the periodic table of elements was discovered by a Russian chemist Dimitri Mendeleev in 1869.
Read the article about Dmitri Ivanovich Mendeleev and choose the best ending for each statement.
2.
Science is everywhere. It gives us the answers to all the questions and helps to understand the world around us. Scientific discoveries have made our life better. Let's have a look at some of them
3.
In this part you will solve the Math problems based on the biography of Stephen Hawking, a world-renowned British theoretical physicist, known for his contributions to the fields of cosmology, general relativity and quantum gravity, especially in the context of black holes.
4.
In this part you will show your Reading and Listening skills and knowledge of English vocabulary.
5.
Listen to the following talk about the development of the antibiotic medicine called penicillin, and answer the questions below.
6.
Dmitri Ivanovich Mendeleev, the youngest of fourteen children, was born in Tobolsk, Siberia, on 7th February, 1834. His father died when Dmitri was quite young and his mother ran a glass-making factory to support her large family. By the age of fourteen, it was clear that Mendeleev had an aptitude for science. His mother tried to make sure that he received a decent education. However, her plans were halted when the glass factory was destroyed by fire.
Eventually, Mendeleev was admitted to university in St Petersburg. He was happy there, until yet another setback threatened to prevent him from reaching his potential. He fell seriously ill and was forced to stay at home in bed for days, sometimes weeks. He was only able to complete his degree through the help of his teachers and fellow students who would visit him often with books to read and papers to write. In 1856, Mendeleev was awarded his degree, and he soon completed his doctorate and was awarded the post of Professor of Chemistry at the University of St Petersburg.
It was not until the last few years of the 1860s that he was to begin work on what we now know to be his great achievement - the arranging of the elements into the Periodic Table. At that time they were distinguished by their atomic weight. This characteristic had been proposed by the British chemist, Dalton, more than 50 years earlier. Mendeleev took Dalton’s work and improved it. He grouped the elements by their atomic weight and by the similarities they possessed in their properties. There were gaps in the table and Mendeleev believed that in the future new elements would be discovered to fill those gaps. His predictions were correct. Three of those elements were found during his lifetime: gallium, scandium, and germanium. They provided the strongest support for his periodic table. The table has now become fundamental to our understanding of chemistry and of how the universe is put together.
In Russia, the Tsar considered Mendeleev’s politics too liberal, and consequently Mendeleev resigned from the university in 1900. He remained a popular figure with the Russian people and was appointed Director of the Bureau of Weights and Measures in 1903. He continued in this post until his death from pneumonia on 20th January, 1907.
7.
Read the text about Eureka moments and write the correct form of the words given in brackets.
8.
That is the end of the test. Now you can send your answers.
Thank you!
9.
Year 2019 is announced as the year of the Periodic Table. It was created by Dmitri Mendeleev 150 years ago. This discovery is a very important step in the development of Chemistry.
Chemistry and the Periodic Table of Elements. Questions 11-30.
10.
There have been a lot of famous scientists throughout the history of mankind who have made discoveries and breakthroughs that have changed the world. Here are just a few of them. Match the discoveries and the names.
11.
Read the text about James Clerk Maxwell, a great scientist who studied electromagnetic field. Which order of the paragraphs is correct?
12.
Write your text here
13.
To prove his theory of the Big Bang Stephen Hawking solved 15 complicated equations, one at a time. The first equation took him 1 day to solve, the second took him 2 days to solve, the third took him 3 days to solve, and so on, with each equation taking him 1 more day to solve than the previous one. Stephen solved the first equation on a Monday, and the second on a Wednesday. On what day of the week did he finish his 15th equation?
A.
Sunday
B.
Monday
C.
Wednesday
D.
Friday
E.
Saturday
Correct Answer
B. Monday
Explanation Stephen solved the first equation on a Monday and the second on a Wednesday. This means that there is a gap of 2 days between the first and second equations. Since each equation takes one more day to solve than the previous one, the third equation would take 3 days to solve. Therefore, the gap between the second and third equations would be 3 days. Continuing this pattern, we can see that the gap between the 14th and 15th equations would be 15 days. Adding this gap to the day Stephen solved the 14th equation (which is a Monday) would give us the day he finished his 15th equation, which is also a Monday.
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14.
Given that approximately 76% of all the Chlorine atoms on Earth are Chlorine-35. and 24% of them are Chlorine-37, what is the atomic mass of Chlorine?
A.
It is 35.2 (approx.)
B.
It is 35: We ignore 37Cl because it’s an isotope.
C.
It is 36: We take the average of the two masses: (35+37)/2 = 36
D.
It is approximately 35.5: It’s calculated as follows: 0.76x35+0.24x37 = 35.5 (approx.)
Correct Answer
D. It is approximately 35.5: It’s calculated as follows: 0.76x35+0.24x37 = 35.5 (approx.)
Explanation The atomic mass of Chlorine is approximately 35.5. This is calculated by multiplying the percent abundance of Chlorine-35 (76%) by its atomic mass (35), and adding it to the percent abundance of Chlorine-37 (24%) multiplied by its atomic mass (37). So, (0.76 x 35) + (0.24 x 37) equals 35.5 (approx.).
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15.
His mother’s plans for his education ...
A.
Were that he should have the best.
B.
Were halted by his father's death.
C.
Were ruined by the fire.
D.
Started because of his great scientific promise.
Correct Answer
C. Were ruined by the fire.
Explanation The correct answer is "were ruined by the fire." This suggests that the mother's plans for the person's education were destroyed or disrupted due to a fire incident.
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16.
To complete his degree, Mendeleev ...
A.
Was helped by his mother.
B.
Attended St Petersburg University.
C.
Made good progress.
D.
Was helped by teachers and students.
Correct Answer
D. Was helped by teachers and students.
Explanation Mendeleev completed his degree with the help of teachers and students. This suggests that he received assistance and support from both his instructors and peers throughout his academic journey. Their guidance and collaboration likely played a significant role in his successful completion of his degree.
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17.
Mendeleev arranged elements by their weight...
A.
As Dalton had proposed.
B.
And grouped them by mass.
C.
And grouped them by their properties.
D.
And organized them by colour.
Correct Answer
C. And grouped them by their properties.
Explanation Mendeleev arranged elements by their weight, as Dalton had proposed. However, he went a step further and grouped them by their properties. This means that elements with similar properties were placed together, allowing for a better understanding of their behavior and relationships. By organizing the elements in this way, Mendeleev was able to create the periodic table, which is still used today to classify and study elements based on their properties.
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18.
He predicted new elements would be found ...
A.
Because there were gaps in his table.
B.
Within the next three years.
C.
By deducing their properties.
D.
To provide support for his ideas.
Correct Answer
A. Because there were gaps in his table.
Explanation The correct answer is "because there were gaps in his table." This is because the existence of gaps in the periodic table indicated that there were elements yet to be discovered. Mendeleev predicted the existence and properties of these unknown elements based on the patterns and trends he observed in the known elements. His predictions were later confirmed when the predicted elements were discovered, providing support for his ideas and the accuracy of the periodic table.
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19.
Mendeleev resigned from the university because ...
A.
He was getting too old.
B.
He became Director of the Bureau of Weights and Measures.
C.
He had caught pneumonia.
D.
Of his politics.
Correct Answer
D. Of his politics.
Explanation Mendeleev resigned from the university because of his politics. This suggests that his political beliefs or activities were the reason for his resignation. It is likely that his political views clashed with the university's administration or policies, leading to his decision to leave.
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20.
Isotopes are atoms of an element ... .
A.
With the same number of protons but different number of neutrons.
B.
That are radioactive.
C.
With a magnetic charge.
D.
With the same number of electrons but different numbers of protons.
Correct Answer
A. With the same number of protons but different number of neutrons.
Explanation Isotopes are atoms of an element with the same number of protons but different number of neutrons. This means that isotopes have the same atomic number (which is determined by the number of protons) but different atomic masses (which is determined by the number of protons plus neutrons). This variation in the number of neutrons gives isotopes different physical properties and stability, but they still belong to the same element because they have the same number of protons and therefore the same chemical properties.
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21.
A(n) ___________ is a simple, pure substance that cannot be broken down further into a more simpler kind of substance.
A.
Alloy
B.
Compound
C.
Element
D.
Crystal
Correct Answer
C. Element
Explanation An element is a simple, pure substance that cannot be broken down further into a more simpler kind of substance. It consists of only one type of atom and cannot be separated into different components by physical or chemical means. Examples of elements include hydrogen, oxygen, and gold.
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22.
Is Nitrogen a good conductor of electricity?
A.
Yes, it is.
B.
It’s an insulator in normal temperature, but becomes a conductor if liquified
C.
Not at all! Nitrogen is an insulator
D.
Yes, in most situations.
Correct Answer
C. Not at all! Nitrogen is an insulator
Explanation Nitrogen is not a good conductor of electricity. It is an insulator, meaning it does not allow the flow of electric current easily. While it is true that nitrogen can become a conductor if it is liquified, the statement "Nitrogen is a good conductor of electricity" is incorrect.
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23.
A chlorine atom attains an octet by
A.
Gaining one electron
B.
Gaining eight electrons
C.
Losing one electron
D.
Losing five electrons
Correct Answer
A. Gaining one electron
Explanation A chlorine atom has 7 valence electrons in its outermost energy level. To attain an octet (8 electrons in the outermost energy level), it needs to gain one electron. This will give the chlorine atom a full outer electron shell, making it more stable.
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24.
An atom has 9 protons and 10 neutrons. Its mass number is ...
A.
1
B.
19
C.
9
D.
10
Correct Answer
B. 19
Explanation The mass number of an atom is the sum of the number of protons and neutrons in its nucleus. In this case, the atom has 9 protons and 10 neutrons, so the mass number would be 9 + 10 = 19.
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25.
An element in Period 3, Group 7 has ...
A.
7 electrons as total, 3 of them in its valence layer
B.
3 electrons in its valence layer and 7 energy levels
C.
3 electrons in its valence layer and 4 energy levels
D.
7 electrons in its valence layer and 3 energy levels
Correct Answer
D. 7 electrons in its valence layer and 3 energy levels
Explanation The answer "7 electrons in its valence layer and 3 energy levels" is correct because elements in Period 3 have a total of 3 energy levels and Group 7 elements have 7 electrons in their valence layer. This information is based on the periodic table, where the period number indicates the number of energy levels and the group number indicates the number of valence electrons.
Transition metals, such as: chromium(Cr), manganese(Mn), iron(Fe), cobalt(Co), nickel(Ni) and copper(Cu).
Correct Answer
A. Helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn)
Explanation The elements helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) are the least reactive because they have full valence electron shells. This means that they have stable electron configurations and do not readily gain or lose electrons to form compounds. As a result, they have very low reactivity and are often referred to as noble gases.
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27.
Which metal is the best conductor of electricity?
A.
Iron
B.
Copper
C.
Silver
D.
Gold
Correct Answer
C. Silver
Explanation Silver is the best conductor of electricity among the given options. This is because silver has the highest electrical conductivity of any metal. It has a high number of free electrons that can easily move through its atomic structure, allowing for the efficient flow of electric current. Copper is also a good conductor, but silver surpasses it in terms of conductivity. Iron and gold have lower conductivity compared to silver and copper.
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28.
Atoms with the same elements with different numbers of neutrons are called .... .
A.
Isomers.
B.
Metalloids.
C.
Isotopes.
D.
Polymers.
Correct Answer
C. Isotopes.
Explanation Atoms with the same elements but different numbers of neutrons are called isotopes. Isotopes have the same number of protons and electrons, giving them the same chemical properties, but they differ in their atomic mass due to the varying number of neutrons. Isotopes can have different physical properties and may be stable or radioactive.
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29.
Which elements are liquids in normal temperature?
A.
Florine, Chlorine, Bromine and Iodine.
B.
Only Chlorine, Bromine.
C.
Only Bromine and Mercury.
D.
No elements are liquids in normal temperature.
Correct Answer
C. Only Bromine and Mercury.
Explanation The correct answer is Only Bromine and Mercury. This is because at normal temperature, both Bromine and Mercury exist in liquid form. Florine and Chlorine are gases at normal temperature, while Iodine is a solid.
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30.
Hydrogen atom has just one electron located at the first energy layer (orbit) whose capacity is 2 electrons. Therefore hydrogen is considered as:
A.
A non-metal
B.
A halogen (like Florine, Chlorine, Bromine and Iodine), because it’s like the halogens, lacks for just one electron to complete its valence shell (outer shell).
C.
An alkali metal (like lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs)), because it’s like them, possess just one electron at its valence shell.
D.
Both as a halogen and an alkali metal; it has a dual nature.
Correct Answer
D. Both as a halogen and an alkali metal; it has a dual nature.
Explanation Hydrogen atom has just one electron located at the first energy layer (orbit) whose capacity is 2 electrons. Therefore, hydrogen can be considered as both a halogen and an alkali metal. Like halogens, hydrogen lacks just one electron to complete its valence shell, and like alkali metals, it possesses just one electron at its valence shell. This dual nature of hydrogen makes it unique and different from other elements.
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31.
Choose one fact about Chlorine that is not correct.
A.
It was recognized as a gas by the Flemish chemist and physician Jan Baptist van Helmont around 1630.
B.
It is obtained mainly by the electrolysis of salts.
C.
It is obtained mainly by the electrolysis of salts.
D.
Compounds of this element are used to disinfect water in swimming pools.
Correct Answer
C. It is obtained mainly by the electrolysis of salts.
Explanation Chlorine is not obtained mainly by the electrolysis of salts. It is actually obtained through the process of electrolysis of brine (sodium chloride solution). This process is known as the chloralkali process.
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32.
Choose one fact about Carbon monoxide that is not correct.
A.
It is part of the volcanic gases.
B.
It is dangerous and can cause massive suicide of whales.
C.
It is used in food industry for meat colouring.
D.
It is used to increase agricultural productivity.
Correct Answer
D. It is used to increase agricultural productivity.
Explanation Carbon monoxide is not used to increase agricultural productivity. It is a toxic gas that is produced by the incomplete combustion of carbon-based fuels. It is not used in the food industry for meat coloring either. Carbon monoxide is commonly found in volcanic gases, and exposure to it can be dangerous and even fatal. It is also known to cause mass suicide events in whales when they are exposed to high levels of carbon monoxide in the water.
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33.
Choose one fact about Silicon that is not correct.
A.
The crystal structure of this substance is the same as that of diamond.
B.
It is used as a conductor/semiconductor.
C.
This is the most common chemical element on Earth after oxygen.
D.
It is part of the river sand.
Correct Answer
B. It is used as a conductor/semiconductor.
Explanation Silicon is not used as a conductor/semiconductor. It is actually a semiconductor material. Conductors, such as metals, have high electrical conductivity, while insulators have low electrical conductivity. Semiconductors, on the other hand, have intermediate electrical conductivity. Silicon is widely used in electronic devices and integrated circuits due to its semiconductor properties. It is able to conduct electricity under certain conditions, making it suitable for applications in transistors, diodes, and solar cells.
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34.
Is it true or false? Substances consisting of two elements, one of which is oxygen are called Oxides.
A.
True
B.
False
Correct Answer
A. True
Explanation Oxides are indeed substances consisting of two elements, one of which is oxygen. This term is commonly used in chemistry to describe compounds formed when oxygen combines with another element. Examples of oxides include carbon dioxide (CO2), iron oxide (Fe2O3), and sulfur dioxide (SO2). Therefore, the statement "Substances consisting of two elements, one of which is oxygen are called Oxides" is true.
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35.
Is it true or false? Distilled water does not contain impurities.
A.
True
B.
False
Correct Answer
A. True
Explanation Distilled water is created through a process that involves boiling water and collecting the condensed steam. This process effectively removes impurities such as minerals, chemicals, and microorganisms, resulting in a purer form of water. Therefore, distilled water does not contain impurities, making the statement "True" correct.
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36.
What is the molar volume of any gas?
A.
2 l ∕ mol
B.
2.4 l ∕ mol
C.
22.4 l ∕ mol
D.
4.2 l ∕ mol
Correct Answer
C. 22.4 l ∕ mol
Explanation The molar volume of any gas is 22.4 L/mol. This value is derived from the ideal gas law, which states that at standard temperature and pressure (STP), one mole of any gas occupies a volume of 22.4 liters. This relationship allows for easy conversion between the number of moles of a gas and its volume, making it a useful concept in chemistry and physics.
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37.
Unit of measurement of the amount of a substance is called a ... .
A.
Gram
B.
Kilogram
C.
Mole
D.
Litre
Correct Answer
C. Mole
Explanation A mole is the unit of measurement used to quantify the amount of a substance. It represents the number of atoms, molecules, or ions in a given sample. The mole is defined as the amount of a substance that contains as many elementary entities (atoms, molecules, or ions) as there are atoms in exactly 12 grams of carbon-12. It is widely used in chemistry to calculate chemical reactions, determine molecular weights, and compare different substances. The other options, gram, kilogram, and litre, are units of mass and volume, but they do not measure the amount of a substance.
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38.
What are the soluble bases called?
A.
Salt
B.
Solution
C.
Alkali
D.
Acid
Correct Answer
C. Alkali
Explanation Soluble bases are called alkalis. Alkalis are a type of base that can dissolve in water to form a solution. They are characterized by their ability to release hydroxide ions (OH-) in water. Examples of alkalis include sodium hydroxide (NaOH) and potassium hydroxide (KOH). These substances are commonly used in cleaning products, soaps, and in various industrial processes. They have a bitter taste and a slippery feel.
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39.
Time is circular - no beginning, no end. Stephen Hawking was born on January 8, 1942, on the 300th anniversary of Galileo's death, and died at 76 on March 14, 2018 on the 139th anniversary of Einstein's birth. Imagine we take the number of years between the death of Galileo and the birth of Einstein and add the number of years between the birth of Einstein and the birth of Hawking. What is the result? You need to round all the results to the nearest year.
________
Correct Answer 300
40.
Before his illness, Steven Hawking was a cox in Oxford Rowing Team. Suppose the team rowed a boat downstream for 42 miles. The return trip upstream took 8 hours longer. If the current flew at 2 mph, how fast did they row in still water?
________ mph
Correct Answer 5
Explanation The speed of the current is given as 2 mph. Since the team rowed downstream, the speed of the boat relative to the still water would be the sum of their rowing speed and the speed of the current, which is 2 mph. Let's assume the rowing speed in still water is x mph. Therefore, the speed downstream would be x + 2 mph. The distance traveled downstream is 42 miles. On the return trip upstream, the speed of the boat relative to the still water would be the difference between their rowing speed and the speed of the current, which is x - 2 mph. The distance traveled upstream is also 42 miles, but it took 8 hours longer. Using the formula time = distance/speed, we can set up the equation 42/(x + 2) = 42/(x - 2) + 8. Solving this equation, we find that x = 5 mph, which is the speed of the boat in still water.
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41.
Palindromes have always fascinated Hawking. Once he was going in a car when his driver glanced at the mileage indicator and happened to notice that it displayed a palindromic number: 13931. Two hours later to his surprise it again displayed another palindrome. What average speed was Steven's car travelling, assuming its average speed was less than 70 mph?
________ mph
Correct Answer 55
42.
Stephen Hawking found it possible to encounter the aliens.
Suppose a number of aliens, who have just dropped in from another planet, emerge from their spacecraft.
there is more than one alien
each alien has the same number of fingers
each alien has at least one finger on each hand
the total number of fingers of all the aliens is between 200 and 300
the number of fingers each alien has is equal to the number of aliens
How many aliens are there? ________
Correct Answer 17
Explanation If there are 17 aliens, and each alien has the same number of fingers as the number of aliens, then each alien would have 17 fingers. Since each alien has at least one finger on each hand, they would have a minimum of 34 fingers. If there are more than one alien and each alien has the same number of fingers, then the total number of fingers of all the aliens would be a multiple of the number of aliens. The only multiple of 17 that falls between 200 and 300 is 17 x 17 = 289. Therefore, there are 17 aliens.
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43.
Suppose a ufologist recently reported a strange object, which he described as being in the shape of a quasi-pyramid, hovering over a cornfield. If you add the number of edges this figure has to its number of faces, what total do you arrive at?
A.
28
B.
46
C.
36
D.
38
Correct Answer
B. 46
44.
Stephen Hawking died on the day of π, which is observed on March 14 since 3, 1, and 4 are the first three significant digits of π.
Solve this Pi-problem. Pictured below are three identical boxes packed with pies. Which box contains the most pie? You can assume that all pies are exactly the same height.
A.
A has the most pie
B.
B has the most pie
C.
C has the most pie
D.
A, B and C have equal amounts
Correct Answer
D. A, B and C have equal amounts
Explanation The question states that all three boxes are identical and packed with pies. Therefore, each box contains the same amount of pie.
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45.
In 2008 Steven Hawking's Questioning the universe video was uploaded to a website where viewers can vote if they like or dislike the video. The video begins with a score of 0, and the score increases by 1 for each like vote and decreases by 1 for each dislike vote. After several minutes the video had a score of 90, and that 65% of the votes cast on his video were like votes. How many votes had been cast on Hawkins' video at that point?
A.
200
B.
300
C.
400
D.
500
Correct Answer
B. 300
Explanation If the video starts with a score of 0 and after several minutes it has a score of 90, it means that there have been 90 more likes than dislikes. Since 65% of the votes were likes, it means that 35% were dislikes. Therefore, the difference between likes and dislikes is 65% - 35% = 30%. If this 30% represents 90 votes, then 100% would represent 300 votes. Therefore, 300 votes had been cast on Hawkins' video at that point.
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46.
Hawking wasn't the best student at school. Despite his average grades, both his teachers and his peers seemed to understand that they had a future genius among them, evidenced by the fact that his nickname was "Einstein". Once his Physics' teacher was grading tests of the 15 students in his class and found that when he graded everyone's test except Hawking's, the average grade for the class was 80%. After he graded Hawking's test, the test average became 81%. What was Hawking's score on the test?
A.
85
B.
91
C.
94
D.
95
Correct Answer
D. 95
Explanation The average grade for the class was 80% before Hawking's test was graded. After grading his test, the average increased to 81%. This means that Hawking's score must be higher than the average of 80%. The only option that is higher than 80% is 95, so that must be Hawking's score on the test.
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47.
Hawking studied galaxies. Every ‘dot’ that you can see in the image of the Hubble Deep Field is a galaxy. The area of the Hubble Deep Field image covers 1/32000000 of the sky, or the entire universe. There are 3000 dots, or galaxies, in the Hubble Deep Field.
Use this figure to estimate the number of galaxies in the universe.
________
Correct Answer 96*10^10, 960000000000
Explanation The figure given, 96*10^10 or 960,000,000,000, represents the estimated number of galaxies in the universe. This estimation is based on the fact that the Hubble Deep Field image covers 1/32000000 of the sky, or the entire universe, and contains 3000 galaxies. By scaling up the number of galaxies in the observed area to the entire universe, we can estimate that there are approximately 96*10^10 or 960,000,000,000 galaxies in total.
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48.
Which fact about Alexander Fleming’s life before he became a bacteriologist is true?
A.
Alexander Fleming was born in Scotland in 1891.
B.
Alexander did not follow his family occupation.
C.
He studied medicine at a hospital in Edinburgh.
D.
He was an average student at school and didn't have any special abilities.
Correct Answer
B. Alexander did not follow his family occupation.
Explanation The correct answer is "Alexander did not follow his family occupation." This means that Alexander Fleming did not pursue the same occupation as his family members. The other options state that he was born in Scotland in 1891, he studied medicine at a hospital in Edinburgh, and he was an average student at school and didn't have any special abilities, but these options are not true according to the question.
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49.
What happened when Fleming used a diluted solution of penicillin?
A.
Bacteria of influenza did not grow.
B.
Penicillin worked against many types of bacteria but for those of flu.
C.
He had the flu and couldn't continue his experiments.
D.
He had an accident in his laboratory.
Correct Answer
A. Bacteria of influenza did not grow.
Explanation When Fleming used a diluted solution of penicillin, the bacteria of influenza did not grow. This suggests that penicillin was effective in inhibiting the growth of the influenza bacteria.
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50.
Why was penicillin not used for the public until 1941?
A.
The first penicillin was poisonous and inappropriate for human use.
B.
The first penicillin was very expensive.
C.
Every new medicine should be tested at least for ten years.
D.
The scientists needed to make sure that it was not toxic.
Correct Answer
D. The scientists needed to make sure that it was not toxic.
Explanation The reason why penicillin was not used for the public until 1941 is because the scientists needed to make sure that it was not toxic. The first penicillin produced was potentially poisonous and not suitable for human use. Therefore, extensive testing and research were conducted to ensure its safety before it could be made available to the public.
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