ACT
Practice Test 36

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NATURAL SCIENCE: The Great Pyramid at Giza: Its Composition and Structure

The Great Pyramid at Giza is arguably one of the most fascinating and contentious piece of architecture in the world. In the 1980s, researchers began focusing on studying the mortar from the pyramid, hoping it

Line 5 would reveal important clues about the pyramid’s age and construction. Instead of clarifying or expunging older theories about the Great Pyramid’s age, the results of the study left the researchers mystified. Robert J. Wenke from the University of

10 Washington received authorization to collect mortar samples from some of the famous ancient construction sites. Among these sites was the Great Pyramid. The mortar that Wenke discovered was formed by particles of pollen, charcoal, and other organic matter. By using
15 radiocarbon dating, scientists were able to make some disconcerting discoveries. After adjusting the data, the mortar revealed that the pyramid must have been built between 3100 BC and 2850 BC with an average date of 2977 BC. This discovery was controversial because

20 these dates claimed that the structure was built over 400 years earlier than most archaeologists originally believed it had been constructed. Furthermore, archaeologists discovered something even more anomalous. Most of the mortar samples

25 collected appeared to be little more than processed gypsum with traces of sand and limestone. The sand and limestone found in the gypsum were not added but were actually contaminants of the processed gypsum. The mortar used to build the Great Pyramid is of an

30 unknown origin. It has been analyzed repeatedly and its chemical composition has been established. However, even using modern techniques, scientists have been unable to reproduce it. The gypsum mortar is stronger than the stone on the pyramid and the mortar is still
35 intact today, thousands of years after the pyramid was built. This mortar was not used to bond the heavy stone blocks together like cement mortar does with modern bricks. Instead, the gypsum mortar’s role was to buffer the joints and to reduce friction as the enormous blocks

40 were put into place. Examining the mortar from the Great Pyramid assists scientists in making inferences about Egypt’s past. Researchers questioned why the Egyptian builders would choose to use gypsum mortar over lime mortar.

45 Egypt had numerous limestone mines that could have been used to create a more durable lime mortar. Despite the abundance of lime, there is no evidence of lime mortar being used in Egypt until 2500 years after the pyramids were built. Researchers then began to determine

50 why the more water-soluble gypsum would have been preferred. They discovered that gypsum would have been easier to mine than limestone. In addition, the Egyptian builders discovered that when gypsum is heated to approximately 265 degrees Fahrenheit, some

55 of the moisture is excluded. When the processed gypsum is mixed with water again, the resulting substance is used for the mortar. Despite having significant mineral resources, Egypt has few natural fuels available. The 265 degree

60 Fahrenheit temperatures needed to process the gypsum and turn it into mortar can be achieved with the heat of an open fire. On the other hand, to make lime mortar, extremely high temperatures of around 1800 degrees Fahrenheit are needed. Most historians conjecture that

65 the high heat needed to process limestone is the reason lime mortar was not used. The shortage of natural fuel sources would most likely have made the creation of lime mortar highly uneconomical.

From the author’s reference to the Great Pyramid at Giza as both “fascinating and contentious,” (line 2) it can be inferred that the Great Pyramid is seen as both:

  • Solution

    The best answer is C. “Fascinating” and “intriguing” are synonyms of one another, both meaning “interesting or exciting.” Likewise, “contentious” and “controversial” are synonyms of one another, both meaning “causing disagreement.” Answer choices A, B, and D do not have pairs of words that mean the same thing as “fascinating” and “contentious.”

According to the passage, the mortar used to build the Great Pyramid included all of the following EXCEPT:

  • Solution

    The best answer is G. The passage states that mortar used in the construction of the Great Pyramid was found to be formed of “particles of pollen, charcoal, and other organic matter,” and that most of the mortar collected was made of “processed gypsum with traces of sand and limestone.” Answer choice G, processed limestone, is the only material not explicitly listed as composing the mortar of the Great Pyramid.

The passage indicates that, unlike gypsum, limestone:

  • Solution

    The best answer is A. The passages tells you that gypsum needs a temperature of 265 degrees Fahrenheit to be turned into mortar; on the other hand, “to make lime mortar, extremely high temperatures around 1800 degrees Fahrenheit are needed.” This best supports answer choice A. Answer choices B, C, and D are not supported by details found in the passage.

Which of the following was NOT a use of the mortar used in constructing the Great Pyramid?

  • Solution

    The best answer is H. The passage states that the gypsum mortar used in constructing the Great Pyramid “was not used to bond the heavy stone blocks together.” This fact supports answer choice H. The passage also goes on to state, “The gypsum mortar’s role was to buffer the joints and to reduce friction as the enormous blocks were placed.” This tells you that answer choices F, G, and J all were uses of the mortar when constructing the Great Pyramid.

It may be reasonably inferred from the passage that for those studying ancient pyramids:

  • Solution

    The best answer is D. Throughout the passage, there are several references to researchers not having conclusive facts and making the best hypotheses they can regarding their findings. For example, the fourth paragraph begins with the statement “Examining the mortar from the Great Pyramid assists scientists in making inferences about Egypt’s past,” and goes on to discuss the conclusions researchers drew based on the findings that they had discovered. Answer choice A may appear to be correct; however, the information given on radiocarbon dating does not provide an exact date of construction. Rather, scientists had to conjecture about the precise date the Pyramid was built, which supports answer choice D. Answer choice B is incorrect because the passage states that after analysis of the gypsum mortar, “even using modern techniques, scientists have been unable to reproduce it.” Answer choice C is beyond the scope of the passage; there is no evidence that the conclusions of scientific researchers and archaeologists usually vary.

The passage indicates that the type of mortar used in the construction of ancient Egyptian pyramids was affected by:

  • Solution

    The best answer is J. The passage states that Egypt “has few natural fuel sources available,” and goes on to say that “The shortage of natural fuel sources would most likely have made the creation of lime mortar highly uneconomical.” This best supports answer choice J. It is stated in the passage that limestone was both more durable and more abundant than gypsum, thus answer choices F and G can be eliminated. The inferences drawn by the researchers are irrelevant to the choice of material that the Egyptians used in constructing the pyramids; therefore, answer choice H is also incorrect.

As it is used in line 6, the word expunging most nearly means:

  • Solution

    The best answer is A. The passage states that “Instead of clarifying or expunging older theories about the Great Pyramid, the results of the study left the researchers mystified.” The word “expunge” means “to get rid of or remove,” so within the context of the passage, the results of the study did not clarify or eliminate any older theories about the Great Pyramid, answer choice A.

Previous to the research discussed in the passage, it was believed that the Great Pyramid was constructed in approximately what year?

  • Solution

    The best answer is H. The passage states that from radiocarbon dating, it was found that the average date of construction for the Great Pyramid was 2977 BC. The passage goes on to state that this discovery was disputed because this date asserted that the Pyramid was built “over 400 years earlier than most archaeologists originally believed.” If archaeologists believed the Pyramid to have been constructed 400 years after 2977 BC, the original date of construction was, therefore, assumed to be approximately 2577 BC.

The passage indicates that researchers believed that examination of the mortar would reveal information regarding the Great Pyramid’s:

  • Solution

    The best answer is B. As stated in the passage, “researchers began studying the mortar from the pyramid, hoping it would reveal important clues about the pyramid’s age and construction.” This supports answer choice B. The topics of the other answer choices are discussed throughout the passage; however, these topics are not the chief topics the researchers were looking to learn from studying the mortar.

According to the passage, which of the following is a reason that gypsum was used to create mortar instead of limestone?

  • Solution

    The best answer is G. The passage states that the gypsum “would have been easier to mine than limestone.” This best correlates with answer choice G. Answer choice F may appear to be correct; however, the passage does not discuss whether a more water-soluble material would be advantageous when making mortar.

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