Water for life

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	Time: 15 hours Level: Introductory

	Introduction Introduction Resource This unit is an introduction to chemistry concepts, using water as the main illustration. Much of the unit is devoted to exploring the smallest water particle – a water molecule – what it is and how it...

	1 The power of water 1 The power of water Resource The ways in which human activities interact with the water cycle can have devastating consequences for all forms of life. These range from the very large scale – for example, the effects of the movement...

	2 Earth's store of water 2.1 Where water occurs and how we measure it Resource When astronauts first ventured to the Moon in the late 1960s, they were captivated by a vision of the Earth in colour as it had never been seen before (Figure 2). It is not surprising that, after pictures... 2.2 Going up: using scientific notation for large numbers Resource Think again about the value for the total volume of water stored on Earth: 1460 000 000 km3. 2.3 The study of a raindrop Resource Most of the usable water is derived from the 1.1 × 105 km3 that falls over the land surface each year as rain, snow, sleet or hail. The collective term for all of these sources of water is precipitation.... 2.4 Going down: using scientific notation for small numbers Resource You saw in Section 2.2 how the powers of ten notation provides a concise method of expressing very large numbers and reduces the chances of errors when, otherwise, many zeros would have to be written out.... 2.5 What is water made of? Resource The size of a water droplet may seem very small but in terms of the scale of scientific measurement it is relatively large. You already know that water is made up of molecules so now consider a water droplet... 2.6 Models of a water molecule Resource In this kind of building set, there are a limited number of types of block and each block has a particular shape. Just as importantly, each one has a particular way in which it can link to other blocks... 2.7 The ‘salt’ in seawater Resource 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.

	3 What are compounds? 3 What are compounds? Resource Click on the video clip to watch Elements and Compounds, which focuses on water and its constituent elements.

	4 Inside the atom 4 Inside the atom Resource 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?

	5 Molecules and covalent bonding 5 Molecules and covalent bonding Resource 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...

	6 Chemical language 6.1 Introduction Resource The previous sections in this unit include many terms which may have been unfamiliar to you: for example, atom, element, compound, molecule and bond. Chemistry has a language all of its own and grasping... 6.2 Chemical symbols Resource So far, atoms have been represented as labelled spheres or circles and the bonds that link atoms in molecules have been represented as lines. This is a rather cumbersome method of writing down molecules.... 6.3 Chemical formulas Resource By using symbols, elements can be represented much more conveniently and much more briefly. This method of using symbols can be extended to compounds. You will now look further into this idea using a very... 6.4 Chemical equations and chemical reactions Resource The previous section shows how different elements can either exist on their own or combine with other elements to make compounds. This section builds on these ideas by looking at chemical reactions in...

	7 Ions and ionic bonding 7 Ions and ionic bonding Resource This section returns to bonding – the way in which atoms are joined to each other. You have already met one type of bonding involving covalent bonds, which is found in molecules. However, this is not the...

	8 Water and its impurities 8 Water and its impurities Resource Water must be of a certain quality to be suitable for human consumption. No natural water found on Earth is pure; any sample of water contains more than just water molecules. Some materials, such as sodium...

	9 Unit summary 9 Unit summary Resource You have learned about the following concepts in this unit:

	References and Acknowledgements Acknowledgements Resource