Elements,+Compounds+and+Mixtures

** ‍Elements **
 * Elements, Compounds and Mixtures **

** ‍ **All known materials that we, as curious humans, have studied consist of tiny, individual blocks of matter called atoms. Atoms have been categorised into over 100 different types which are referred to as the Elements. These elements are again subdivided into the categories of metals and non-metals. All of the Elements are listed in what is known as the Periodic Table.



An element can be defined as the smallest possible unit of a substance, which cannot be decomposed any further and which has a specific and identifiable number of protons in the nucleus. ‍All of the Elements have their own symbol which are used consistently across the world so that scientists can identify them quickly and accurately. As primary teachers we should have a sound awareness of what the elements are and how we should refer to them. A useful website for technical definitions can be found here:

@http://www.chemistry-dictionary.com/

For a more simplisitic, child friendly version go to bitesize:

@http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway/periodictable/fundamentalrev1.shtml

If you are still having some difficulties getting to grips with it all then have a quick nosy at this brilliant tune by They Might be Giants- it might just help you understand!

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Here is link to a song to help you learn the first 10 elements of the period table - not that Primary children will have to go into that much depth, but it never hurts to have a song to re-inforce things when you are learning it yourself!

[] ** Compounds **are combinations of two or more different elements which are linked together in some way. They have to be different elements or they are still just considered elements - so H2 (which is how hydrogen is generally found) isn't a compound (it is a diatomic element, to be precise), but H2O (water) is because its a combination of hydrogen and oxygen. There are a few different ways the elements can be linked together but the main two are ionic and covalent bonds. To tell you how each of these work I'll have to explain a bit about how molecules work. Every atom has a nucleus, made up of neutrally charged neutrons and positively charged protons. So the nucleus has a positive charge. Just like magnets, positive things attract negative things so orbiting around the nucleus are electrons, small negatively charged particles. Electrons want to be as close to the positive nucleus as they can get, but there is only enough space for 2 to surround it in the first "shell". After that the next shell can hold 8, as can each shell after that. Because of this limit per shell, atoms with full outer shells (ie 2 electrons in first shell, or 8 electrons in any other shell) are the most stable and least likely to react with other things. All of the group 8 elements (far right of the periodic table) have full outer shells so are very unreactive (eg neon).

A** mixture **contains two or more elements or compounds, with a significant difference to compounds being that no chemical reaction takes place when creating a mixture. Therefore the components can usually be separated through physical means, such as filtration, evaporation, or distillation. An important factor to remember when separating a mixture is that energy is neither used nor gained. The specific components in a mixture will not change their properties, for example when iron filings are mixed with another substance, they will still be attracted to a magnet: Another difference from a compound, is that a mixture has a 'variable composition', meaning that you do not have to add or take away a specific amount of a component. Examples of mixtures are sea, air, and water.




 * To find more information on this, with links to other useful pages, go to: **

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 * The BBC KS3 bitesize website has an excellent page ([]) to improve your knowledge of materials, and within this, there are links to elements, compounds and mixtures. As it is aimed at KS3,** **it will be more advanced than lessons taught in Primary school. However, it will help develop your knowledge of this area of the curriculum, and the information and activities can be adapted in a way to fit whatever Key stage you are teaching. For example, according to the National curriculum, the follwing criteria must be fulfilled by KS2:**

"Changing materials
2. Pupils should be taught:


 * 1) to describe changes that occur when materials are mixed [for example, adding salt to water]
 * 2) [|to describe changes that occur when materials [for example, water, clay, dough are heated or cooled]]
 * 3) that temperature is a measure of how hot or cold things are
 * 4) about reversible changes, including dissolving, melting, boiling, condensing, freezing and evaporating
 * 5) [|the part played by evaporation and condensation in the water cycle]
 * 6) that non-reversible changes [for example, vinegar reacting with bicarbonate of soda, plaster of Paris with water] result in the formation of new materials that may be useful
 * 7) that burning materials [for example, wood, wax, natural gas] results in the formation of new materials and that this change is not usually reversible.

Separating mixtures of materials
3. Pupils should be taught:


 * 1) how to separate solid particles of different sizes by sieving [for example, those in soil]
 * 2) that some solids [for example, salt, sugar] dissolve in water to give solutions but some [for example, sand, chalk] do not
 * 3) how to separate insoluble solids from liquids by filtering
 * 4) how to recover dissolved solids by evaporating the liquid from the solution
 * 5) to use knowledge of solids, liquids and gases to decide how mixtures might be separated."