Earth's physical resources: petroleum
The discovery of the world's first major underground oil field in Pennsylvania, USA in 1859 sparked the continuing era of the world's reliance on cheap energy from oil and gas. This free course, Earth's physical resources: petroleum, begins by examining the geological characteristics of petroleum and the key ingredients necessary to form oil and gas accumulations. Then there is a brief description of industrial operations during the life cycle of an oil field, starting with subsurface analysis a
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Test kits for water analysis
This free course, Test kits for water analysis, steps outside the laboratory to look at some examples of analytical procedures being carried out in the field using commercial test kits. These quick tests provide results on-site, extending the options available to analysts. The methods used are chemical or microbiological in nature, made portable by microelectronics.Author(s): Creator not set

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Acknowledgements

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6.3 Valence-shell electron-pair repulsion theory

The theory of molecular shape that we have been working towards is called valence-shell electron-pair repulsion theory (VSEPR theory). When applied to molecules and ions of the typical elements, its success rate is high. Here is a stepwise procedure that you can follow when applying this theory. It is illustrated with the molecule XeF4 and the ion C1O3. Xenon tetrafluoride is one of the select band of noble gas compounds that were unknown before 1962
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4.5.2 Noble gas configurations under stress

It is remarkable how many molecules and ions of the typical elements can be represented by Lewis structures in which each atom has a noble gas shell structure. Nevertheless, many exceptions exist. According to the periodic trends summarised in Section 2, the highest fluorides of boron and phosphorus are BF3 and PF5. How
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4.5.1 Lewis structures

G.N. Lewis used the shared electron-pair bond to re-express structural formulae in an electronic form. Examples appeared in Figure 28, where the sharing leads to Lewis structures in which each atom has the shell structure of a noble gas.


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4.3 Metallic bonding

Two familiar properties of metals point to a simple model of metallic bonding. Firstly, metals have a strong tendency to form positive ions. Thus, when sodium reacts with water, and when magnesium and aluminium react with acids, hydrogen gas is evolved and the ions Na+(aq), Mg2+(aq) and Al3+(aq), respectively, are formed. Secondly, metals are good conductors of electricity: when a voltage difference is applied
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3.3 Electronic configurations and the Periodic Table

Figure 21 has been designed for use in a particular thought experiment. The purpose of the thought experiment is to see how the electronic configuration of the atoms changes as one moves through the Periodic Table from beginning to end. We start with the hydrogen atom, which has one proton and one electron. Then we
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Money talks: More 'glanceability'


Author(s): The Economist

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9 Summary

Now you will be very familiar with cardiovascular diseases, their development and their diagnosis. You will also know their treatment and many of the cardiovascular disease risk factors – what they are and how they can be influenced positively to minimise cardiovascular diseases. You will understand the overall importance of a balanced diet, regular exercise and weight management (guided by adiposity measurements) throughout life, to maintain cardiac and vascular health. You will also be a
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Introduction

You may have met complex numbers before, but not had experience in manipulating them. This course gives an accessible introduction to complex numbers, which are very important in science and technology, as well as mathematics. The course includes definitions, concepts and techniques which will be very helpful and interesting to a wide variety of people with a reasonable background in algebra and trigonometry.

This OpenLearn course provides a sample of Level 3 study in Author(s): The Open University

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Copyright © 2016 The Open University

5.1 Arithmetic with real numbers

At the end of Section 1, we discussed the decimals and asked whether it is possible to add and multiply these numbers to obtain another real number. We now explain how this can be done using the Least Upper Bound Property of Author(s): The Open University

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4.3 Least Upper Bound Property

In the examples just given, it was straightforward to guess the values of sup E and inf E. Sometimes, however, this is not the case. For example, if then it can be shown that E is bounded above by 3, but it is not so easy to guess the least upper bound of E.

In such cases, it i
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1.2 Decimal representation of rational numbers

The decimal system enables us to represent all the natural numbers using only the ten integers which are called digits. We now remind you of the basic facts about the representation of rational numbers by decimals.


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Does it make sense?

Example 3

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1.3.1 Try some yourself

1 The new home owners from Example 4 above want to price grass seed, as well as the turf (transport only). The best buy seems to be loose seed, which says ‘1 kilo covers 80 m2’. They wonder what length the side of an 80 m2
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Acknowledgements

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Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit:

Example 3 Table: Copyri
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3.4.1 Try some yourself

1 Write down the coordinates of the point P on each of the graphs below and interpret these coordinates in terms of the labels on the axes.

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3.2 Negative coordinates

Up to now only those points with positive or zero coordinates have been considered. But the system can be made to cope with points involving negative coordinates, such as (2, 3) or (2, 3). Just as a number line can be extended to deal with negative numbers, the x-axis and y-axis can be extended to deal with negative coordinates.

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2.3.1 Try some yourself

1 This table categorises Tom's activities for the day.

ActivityTime/hours
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