Measuring the same sample should give the same result every time if the equipment is precise. In practice, the information displayed by a measuring device can depend on several factors (such as temperature and humidity) and can drift slightly over time. Nevertheless, during the time it takes to complete a measurement sequence, all measurements ought to remain within a specified, small margin of error, often marked on the equipment. We will see later on, in Author(s): The Open University

Accuracy is a measure of how close a result is to the true value. Precision is a measure of how repeatable the result is. For instance, a group of three friends tried the shooting gallery at a fair and their targets are shown in Figure 6. The first person was an expert marksman, but they were using a rifle with sights that had not
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If you have less than one unit you should put a zero before the decimal point to make it easier for yourself and others to read the value (e.g. you should write 0.4 rather than just .4, as will be explained later in this unit). However, how many zeros should you put after the last whole number in the series? For instance, is 0.4 the same as 0.40?

The short answer is that on one level, it is. However, by writing 0.40 we are saying that there are four tenths and zero hundredths, an
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Moving up succession, the next lithotectonic unit is the Older Cover. By referring to Figure 9 and Table 2 in conjunction with the
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Geological time can be divided into a number of Eons, Eras and Periods, with further subdivisions into sub-Periods or series and epochs. These are arranged chronologically, with the oldest at the bottom, younging upwards to form the stratigraphic column (Figure 2).

The stratigraphic column can be looked at in
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The panorama was collected by Eugene Andrew Cernan at Station 2. Harrison H. "Jack" Schmitt accompanies Gene on this EVA. (QuickTime, 200KB, note: this may take some time to download depending on your connection speed)

Two of the frames show Al Bean carrying the Apollo Lunar Surface Experiments Package (ALSEP) packages out from the Lunar Module. (QuickTime, 500KB, note: this may take some time to download depending on your connection speed)

This panorama was collected by Neil Armstrong from a spot north east of the landing module at the Sea of Tranquility. (QuickTime, 500KB, note: this may take some time to download depending on your connection speed)

David A. Rothery Teach Yourself Planets, Chapter 6, pp. 66–75, Hodder Education, 2000, 2003.

Look at the Moon even with the unaided eye, and you will see that it has dark patches on a paler background (Figure 2). This simple observation picks out the two distinct types of crust on the Moon. The paler areas are the lunar highlands, and the darker areas are the lunar ‘seas’ or maria (singular: mare). Both the highla
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After studying this unit you will be able to:

• retrieve, evaluate and interpret data and information about the Moon, so that (for example) using a close-up picture of the Moon's surface you could identify the types of feature visible and recognise the processes responsible for creating them;

• interpret simple tables;

• express, manipulate and compare very small numbers.

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Natural gas, which is largely methane, is burned to provide heat for cooking and domestic heating and as an industrial power source. This process of burning involves the reaction of methane with oxygen in air to produce carbon dioxide and water.

A chemical equation can be constructed for the reaction of methane with oxygen to give carbon dioxide and water as the products.

1. The first step is to write the formulas of the reactants on the left and t
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Covalent bonding is one kind of linking that joins atoms together. The group of atoms held together by covalent bonds is a molecule. The example you are most familiar with is the compound water: water consists of covalent molecules, i.e. it is a covalent compound. Recall what is in molecules of water from Section 2.5.

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Before going on to see how atoms can link (bond) with each other, you need to look at atoms in a little more detail. Doubtless they are not like blocks of Lego! So what are they like?

In fact, every atom has a complex internal structure. Given the extremely small size of an atom, you may find it difficult to visualise any smaller bits inside it. However, you may already be familiar with some of the effects of one of these components – electrons. It is easy to do an experiment t
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## Activity 1: Elements and compounds

0 hours 10 minutes

Click on the video clip to watch Elements and Compounds, which focuses on water and its constituent elements.

Click below to v
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The difficulty with having so much of the Earth's water locked up in the oceans is summed up poetically by Coleridge's ‘Ancient Mariner’, becalmed on board ship in the doldrums, beneath a blazing Sun.

Water, water, everywhere,

And all the boards did shrink;

Water, water, everywhere,

Nor any drop to drink.

(Samuel Taylor Coleridge, The Rime of the Ancient Mariner, 179
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Brain imaging and aphasic studies helped us localise the subparts of language processing within the brain. However, they have shed little light on how processing unfolds in real time. This is because contemporary brain imaging is quite poor at showing changes in activity through time in fine detail, so it is hard to pick up something that may be happening slightly before something else.

In the vervet monkey system, calls stand by themselves. Thus there is no syntax. Syntax can be thought of as working like road traffic rules do. It doesn't much matter which side of the road you drive on, as long as there is some clear convention. Similarly in (13), it is necessary to understand the difference between (13a) and (13b) without ambiguity, by having some rule or other about which noun phrase comes first. England may differ from most of the rest of the world in terms of the side o
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To talk about how human language works, we need to establish the meaning of some key terms. The study of language and languages is called linguistics, and linguistics relates closely to biological psychology, as we shall see. Linguists talk about the grammar of a language. By this they don't mean a set of rules about how people should speak. They mean the set of subconscious rules we actually use in formulating phrases and sentences of speech. In this sense, there is no such thing as b
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The document attached below includes the table of contents and first section of Mountain building in Scotland. In this section, you will find the following subsections:

• 1.1 Setting the scene

• 1.2 Recognizing ancient mountains

• 1.3 Orogeny through geological time

• 1.3.1 Geological time: a brief note

• 1.3.2 Disentangling the cont
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In preceding sections we examined two ways in which the auditory system may code frequency information: the place theory and phase locking. In this section we will look at the psychophysical evidence for place coding on the basilar membrane by examining the ability of the auditory system to resolve the components of sinusoidal waves in a complex sound – a phenomenon known as frequency selectivity.

The perception of a sound depends not only on its own frequency and intensity but also o
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