READING PASSAGE 1
You should spend about 20 minutes on Questions 1-13 which are based on Reading Passage 1 on the following pages.
Reading Passage 1 has six sections, A-F.
Choose the correct heading for sections B-F from the list of headings below.
Write the correct number, i-viii, in boxes 1-5 on your answer sheet.
List of Headings
i a significant role to creatures
ii spectrum’s previous models
iii a distinction of hydrogen bonds
iv nature’s mysteries in the small place
v the effect of spectrum on liquid water
vi molecular composition of water
vii water based on infrared light
viii one-body structure of water
1 Section B
2 Section C
3 Section D
4 Section E
5 Section F
The Mysteries of Water
From the nature of dark matter and the origin of the universe to the research for a theory of everything, we come across many mysteries. Whilst these are all puzzles on a grand scale, there is another not quite so grand but equally confusing mystery of the physical world that you can observe from the comfort of your own kitchen. Simply fill a tall glass with chilled water, throw in an ice cube and leave it to stand. The fact that the ice cube floats is the first oddity. And the mystery deepens if you take a thermometer and measure the temperature of the water at various depths. At the top, near the ice cube, you’ll find it to be around o°c, but at the bottom it should be about 4°c. That’s why water is denser at 4°c than it is at any other temperature which is another strange feature that sets it apart from other liquids.
Water’s odd but essential qualities don’t stop there, for ice is less dense than water, and water is less dense at its freezing point than it is when it is slightly warmer. It freezes from the top down rather than the bottom up. So even during the ice ages, life kept going on to flourish on lake floors and in the deep ocean. Also, water has an extraordinary capacity to absorb up heat, and this helps smooth out climatic changes that could otherwise lay waste to ecosystems. However, in spite of water’s enormous importance to life, no single theory had been able to satisfactorily explain its mysterious qualities – until now. If we can believe physicists Anders Nilsson at Stanford University, California, and Lars Pettersson of Stockholm University, Sweden, we could at last be getting to the bottom of many of these anomalies.
Their disputed ideas expand on a theory proposed more than a century ago. According to Wilhelm Roentgen, the man who discovered the X-ray, the molecule in liquid water packs together not in just one way, as today’s textbooks would have US believe, but in two different ways. The way its molecules are composed of two hydrogen atoms and one oxygen atom and how they interact with one another is essential to the understanding of water’s mysteries. The oxygen atom has a slight negative charge whilst the hydrogen atoms share a compensating positive charge. Through this process, the hydrogen and oxygen atoms of neighbouring molecules are drawn to one another, forming a link called a hydrogen bond.
Hydrogen bonds are even weaker than the bonds that link the atoms within molecules together, so keep going to break and reform, but they are at their strongest when molecules are organized so that each hydrogen bond lines up with a molecular bond. The shaping of a water molecule is such that each H20 molecule is surrounded by four neighbours organized in the shaping of a triangular pyramid better known as a tetrahedron. At least, that’s the way the molecules organize themselves in ice. From the conventional view, liquid water has a similar, although less hard, structure, in I which extra molecules are able to pack into some of the open gaps in the tetrahedral arrangement. It explains why liquid water is denser than ice – and it seems to comply with the I results of various experiments that beams of X-rays, infrared light and neutrons are bounced off samples of water.
Some physicists had suggested that water placed under certain extreme conditions may separate into two different structures, but most had assumed it resumes a single structure under normal conditions. And then, 10 years ago, a change found by Pettersson and Nilsson called this idea into question. They were using X-ray absorption spectroscopy to research the amino acid glycine. The peaks in the X-ray absorption spectrum can shed light on the accurate nature of the target substance’s chemical bonds on its structure. Critically, the researchers had got hold of a new, high- ; power X-ray source with which they could make more sensitive and precise measurements than had ever been possible. They soon knew that the water containing their glycine sample was ; producing a far more interesting spectrum than the amino acids did. Nilsson recalls, “What we ; saw there was sensational, so we had to get to the bottom of it.”
The characteristic that sparked their interest was a peak point in the absorption spectrum that is not anticipated by the traditional model of liquid water. Actually, a paper published in 2004 concludes that at any given moment 85% of the hydrogen bonds in water must be weakened or broken. This is far more than the 10% anticipated by the textbook model. The hints of this finding are dramatic: it claims that a total rethink of the strudure of water is needed. So, both Nilsson and Pettersson turned to other X-ray experiments to confirm these claims. Their first move was to enlist the aid of Shik Shin of the University of Tokyo who specialises in a technique called X-ray emission spectroscopy. The main thing about these spectra is that the shorter the wavelength of the X-ray in a substance’s emission spectrum is, the looser the hydrogen bonding must be.
The team struck gold: the two peak spectrum of discharged X-ray might correspond to two separate structures. The researchers insisted that the spike of the longer-wavelength X-ray indicates the proportion of tetrahedrally organized molecules, whilst the shorter-wavelength peak reflects the proportion of disordered molecules. Critically, the shorter-wavelength peak in the X-ray ; emissions was the more intense of the two, suggesting that the loosely bound molecules must be I more outstanding within the sample, an assertion that fitted the team’s previous models. What’s more, they also recognised that this peak shifts to an even shorter wavelength, as if the water was heated, the other peak remains more or less fixed.
Do the following statements reflect the claims of the writer in Reading Passage 1?
In boxes 6-13 on your answer sheet, write
YES if the statement reflects the opinion of the writer
NO if the. statement contradicts the opinion of the writer
NOT GIVEN if it is impossible to say what the writer thinks about this
6 Water’s temperature of top and bottom is generally the same.
7 During the ice ages, there was life in the deep ocean because of warmth.
8 Wilhelm Roentgen discovered X-rays for water molecules.
9 Both hydrogen and oxygen’s atoms are similar to a positive charge.
10 A single H2O molecule is composed entirely of five-angled shape.
11 Pettersson and Nilsson were scrutinising the amino acid glycine by using X-ray absorption spectroscopy.
12 The water including glycine was making a superior spectrum to the amino acid.
13 The shorter wavelength is subjected to the longer wavelength