tag:blogger.com,1999:blog-74039643859014891432024-03-13T01:37:46.524-07:00Cambridge IGCSE Study HelpHelp from someone else who's studying IGCSEs.Unknownnoreply@blogger.comBlogger13125tag:blogger.com,1999:blog-7403964385901489143.post-49958613479327763362016-03-07T08:09:00.000-08:002016-03-07T08:09:16.060-08:00The Eye - Muscles of the IrisThere are two muscles in the iris: the circular muscle and the radial muscle, the diagram below shows both of them<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhi8S2AUeEHk4apxqeMyE3QwqjEaSov-37Et3SNOrSaiX4EuSGTtf0ztOv_DzM-mqdbGxsNCTxD8ikLBmwxQLg6i8eT8YqQitCOrRAAnLu37yH1y4e_uK59yu6EC31zpI1ppiFfweOJHJOf/s1600/Unknown.jpeg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhi8S2AUeEHk4apxqeMyE3QwqjEaSov-37Et3SNOrSaiX4EuSGTtf0ztOv_DzM-mqdbGxsNCTxD8ikLBmwxQLg6i8eT8YqQitCOrRAAnLu37yH1y4e_uK59yu6EC31zpI1ppiFfweOJHJOf/s1600/Unknown.jpeg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Courtesy of http://georgi-georgiev.com/</td></tr>
</tbody></table>
These muscles control the iris, and incase you've forgotten, the iris controls how much light is let into the pupil.<div>
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The two muscles work antagonistically, meaning that when one constricts the other relaxes and when one relaxes the other constricts.</div>
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<span style="font-size: large;"><b><u>What happens in low light concentrations (dark)?</u></b></span></div>
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<span style="font-size: large;"><b><u><br /></u></b></span></div>
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The pupil will widen when it is dark, allowing more light into the eye.</div>
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The radial muscle fibres constrict, widening the eye and the circular muscle relaxes due to the constriction of the radial muscle.</div>
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<span style="font-size: large;"><b><u>What happens in high light concentrations (light)?</u></b></span></div>
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The pupil will narrow when its light, allowing less light into the eye.</div>
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<span style="font-size: large;"><span style="font-weight: bold;"><span style="font-size: small;"><span style="font-weight: normal;">The circular muscle fibres constrict, reducing the pupil size and the radial muscle relaxes due to the constriction of the circular muscle.</span></span></span></span></div>
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<span style="font-size: large;"><span style="font-weight: bold;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></span></span></div>
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<span style="font-size: large;"><span style="font-weight: bold;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></span></span></div>
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<span style="font-size: large;"><span style="font-weight: bold;"><span style="font-size: small;"><span style="font-weight: normal;">Please note that this is a reflex.</span></span></span></span></div>
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<span style="font-size: large;"><span style="font-weight: bold;"><span style="font-size: small;"><span style="font-weight: normal;"><br /></span></span></span></span></div>
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<span style="font-size: large;"><span style="font-weight: bold;"><span style="font-size: small;"><span style="font-weight: normal;">Read about <a href="http://igcsestudyhelp.blogspot.co.uk/2016/03/the-eye-rods-and-cones.html">RODS AND CONES</a> next!</span></span></span></span><br /></div>
Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-7403964385901489143.post-40763289737142523802016-03-07T07:51:00.001-08:002016-03-07T07:52:30.514-08:00The Eye - Rods and Cones There are hundreds of millions of rods and cones covering the surface of the retina of the eye.<br />
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<span style="font-size: large;"><u><b>Cones</b></u></span><br />
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Cones detect colours.<br />
There are around 7 million cones in the human eye.<br />
There are three types of cones, each type detects a different colour, red, green or blue.<br />
When all three types of cones are stimulated equally, we see white.<br />
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<span style="font-size: large;"><u><b>Rods</b></u></span><br />
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Rods detect shapes.<br />
Rods help us see at night, when there isn't enough light for the cones to work.<br />
There are around 120 million rods in the human eye.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_fOTTl2dui8L-BA_5dx8ChU2dW2SJusXVhEslo8-2MtweNfLPeeqiF6CQ45OhsllG05ADrqduqUBsMAIlX__6fFkKKVi-r5GdCiaLISlnA73HTSn2HQXMqpsK_vFVS92BckDnXUAcJxPI/s1600/rods-and-cones.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_fOTTl2dui8L-BA_5dx8ChU2dW2SJusXVhEslo8-2MtweNfLPeeqiF6CQ45OhsllG05ADrqduqUBsMAIlX__6fFkKKVi-r5GdCiaLISlnA73HTSn2HQXMqpsK_vFVS92BckDnXUAcJxPI/s320/rods-and-cones.jpg" width="211" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Courtesy of http://littlewebgiants.com</td></tr>
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You don't have to know what rods and cones look like for the exam, but it might be helpful to see what they look like.</div>
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Look at the <a href="http://igcsestudyhelp.blogspot.com/2016/03/the-eye-fovea.html">FOVEA</a> next!</div>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-7403964385901489143.post-20901211065137940472016-03-07T07:50:00.000-08:002016-03-07T07:50:43.296-08:00The Eye - FoveaThe fovea is the area in the retina where the cones are concentrated. It is also the part of the eye where images are examined in detail.<br />
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Objects within a 2° angle of the eye are the only objects that can be seen in detail. By scanning across scenes, the eye builds up an accurate picture of the object or scene.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEkoyebOxgrLaghyphenhyphendKWtY5YJtzMrVx2eifqt7qRxDchA3Ydooyg6mz85agzmqk_d48dn9WybqHHAv1W-ZQooG-k06oi-6ot-LN7wMk_K9wjoG9dzMxfFLD2o9uwim1VzhMKIbuHrRD94Du/s1600/fovea_centralis-14B94B4319F57D2968C.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="259" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEkoyebOxgrLaghyphenhyphendKWtY5YJtzMrVx2eifqt7qRxDchA3Ydooyg6mz85agzmqk_d48dn9WybqHHAv1W-ZQooG-k06oi-6ot-LN7wMk_K9wjoG9dzMxfFLD2o9uwim1VzhMKIbuHrRD94Du/s320/fovea_centralis-14B94B4319F57D2968C.png" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Image courtesy of www.studyblue.com</td></tr>
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<br />Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-7403964385901489143.post-86407280274796962262016-02-09T10:22:00.000-08:002016-02-09T10:24:51.945-08:00Group 0 - The Noble Gases<span style="font-size: large;"><b><u>What are the noble gases?</u></b></span><br />
<span style="font-size: large;"><b><u><br /></u></b></span>
The noble gases are helium, neon, argon, krypton, xenon and radon (radioactive).<br />
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<span style="font-size: large;"><b><u>Properties of the noble gases</u></b></span><br />
<span style="font-size: large;"><b><u><br /></u></b></span>
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<ul>
<li>They are all non metals</li>
<li>They were discovered after Mendeleev had invented the periodic table</li>
<li>Colourless gases</li>
<li>Exists as monatomic gases, e.g. Ar, Ne, He etc. </li>
<li>Very unreactive</li>
<li>Also called Group VIII</li>
<li>Very steady electron structures that are difficult to change</li>
<li>Other elements try to get these electron configurations by under going chemical reactions</li>
<li>Their outer electron shells are full</li>
</ul>
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Compounds of helium, neon and argon have never been found, but recently, compounds of xenon and krypton with fluorine and oxygen have been found, e.g. XeF.</div>
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<span style="font-size: large;"><b><u>Uses of argon, neon and helium</u></b></span></div>
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<span style="font-size: large;"><b><u><br /></u></b></span></div>
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Neon is used in lasers and neon lights.</div>
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Argon gas is the gas used in lightbulbs that stops the tungsten filament reacting with air.</div>
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Helium is used in balloons and medical procedures, e.g. MRI machines.</div>
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You can separate helium from natural gas by liquefying the other elements.</div>
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You can also obtain the other noble gases by the fractional distillation of liquid air.</div>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-7403964385901489143.post-38850881167801232792016-02-09T09:45:00.000-08:002016-02-09T09:45:38.520-08:00Group VII - The Halogens<span style="font-size: large;"><b><u>What are the elements?</u></b></span><br />
<span style="font-size: large;"><b><u><br /></u></b></span>
The elements in Group VII are fluorine, chlorine, bromine, iodine and astatine (radioactive).<br />
Chlorine, bromine and iodine are the only elements in this group that you need to have an in depth knowledge of.<br />
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<span style="font-size: large;"><b><u>Properties of chlorine, bromine and iodine</u></b></span><br />
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<ul>
<li>They exist as diatomic molecules, e.g Br₂</li>
<li>Their colour darkens as you move down the group - chlorine is pale green, bromine is red-brown and iodine is purple-black</li>
<li>They form molecular compounds with other non-metals, e.g. HCl</li>
<li>As you move down the group they gradually change state, chlorine is a gas, bromine is a liquid and iodine is a solid.</li>
<li>When they react with hydrogen they produce hydrogen halides, for example HCl, and hydrogen halides produce acidic solutions when dissolved in water, for example HCl becomes hydrochloric acid</li>
<li>When they react with metals they produce ionic metal halides, 2FeCl₃ (iron(III) chloride) is an ionic metal halide</li>
</ul>
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<span style="font-size: large;"><b><u>Electronic structure and reactivity</u></b></span></div>
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The reactivity decreases as you go down the group, this is unlike what happens in Groups I and II, the order of reactivity is below:</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhPvjltirKzMg96NBN_ijf8L_n3cW3bpAk3yUZ6N5cLBt9S6BuULD2q8ZJpMNHYE8-hGyqTMzFPqu6J3ge2kMFcxGCR4rRYTn6EyeW0pndDiUGSJIHXByvzMC0NiNUgOIzQnI-of5ZwY_Cs/s1600/Halogen%252520Reactivity%252520Table.bmp" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhPvjltirKzMg96NBN_ijf8L_n3cW3bpAk3yUZ6N5cLBt9S6BuULD2q8ZJpMNHYE8-hGyqTMzFPqu6J3ge2kMFcxGCR4rRYTn6EyeW0pndDiUGSJIHXByvzMC0NiNUgOIzQnI-of5ZwY_Cs/s320/Halogen%252520Reactivity%252520Table.bmp" width="210" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Image courtesy of http://isbchem1.pbworks.com</td></tr>
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When the halogens react, they gain an extra electron. This is because they have 7 electrons in their outer shell (we know this because they're in Group VII) so to fill their outer shell it's easiest to gain 1 electron, rather than loose 7. When that 1 extra electron, they then have the electron configuration of a noble gas.</div>
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The reason chlorine is more reactive than iodine is because chlorine is a smaller atom, so the electrons in the outer shell are held in closer to the nucleus. As you go down the group, the outer electron shell will get further away and will be held less securely.</div>
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<span style="font-size: large;"><b><u><br /></u></b></span></div>
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<span style="font-size: large;"><b><u>Uses of fluorine, chlorine, bromine and iodine</u></b></span></div>
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<span style="font-size: large;"><b><u><br /></u></b></span></div>
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Florine - used for toothpaste and in drinking water</div>
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Chlorine - kills bacteria in drinking water, an ingredient in PVC plastic and is in bleach</div>
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Bromine - used in medicines, fire retardants and disinfectants</div>
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Iodine - used in medicines, disinfectants and is also used as a photographic chemical</div>
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-7403964385901489143.post-20635081484660624812016-02-07T15:30:00.000-08:002016-02-07T15:30:59.947-08:00Group 1 - The Alkali Metals<span style="font-size: large;"><b><u>What are the elements?</u></b></span><br />
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The elements in Group I are:<br />
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<ul>
<li>Lithium</li>
<li>Sodium</li>
<li>Potassium</li>
<li>Rubidium</li>
<li>Caesium </li>
<li>Francium (radioactive)</li>
</ul>
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For IGCSE you need to be aware of all of these metals, but you only need to know the details about the first three.</div>
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All of these metals have to be kept under oil, because they're very reactive, so they can't come into contact with air or water.</div>
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<b><u><span style="font-size: large;">Properties of lithium, sodium and potassium:</span></u></b></div>
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<b><u><span style="font-size: large;"><br /></span></u></b></div>
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<ul>
<li>Soft metals</li>
<li>Good conductors of electricity</li>
<li>Low densities</li>
<li>Low melting points</li>
<li>When freshly cut by a knife, they have a shiny surface</li>
<li>Burn in air, forming white oxides, the white oxides form alkaline solutions of the metal hydroxide when dissolved in water</li>
<li>React vigorously with water, making an alkaline solution of the metal hydroxide and hydrogen gas</li>
<li>React vigorously with halogens (e.g. chlorine) forming metal halides (e.g. sodium chloride)</li>
<li>Potassium reacts the most with water, then sodium and lithium reacts the least with water</li>
</ul>
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Gradual changes (like the one above) are called trends, trends allow chemists to predict things about elements that they have not yet observed.</div>
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The further down the group you go, the more reactive the metals are, so obviously francium is the most reactive. For more information on this look at the post on <a href="http://igcsestudyhelp.blogspot.co.uk/2016/02/the-periodic-table-and-electronic.html">The Periodic Table</a> </div>
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When the Group I elements react, they loose an electron, becoming more stable because their electron configuration is now the same as that of a noble gas. </div>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-7403964385901489143.post-88825338345010114252016-02-07T13:08:00.000-08:002016-02-08T13:47:15.843-08:00The Periodic Table and Electronic Structure<b><u><span style="font-size: large;">History</span></u></b><br />
<span style="font-size: large;"><b><u><br /></u></b></span>
The Periodic Table was invented in 1969 by the Russian scientist Dmitri Mendeleev (at that time, Professor of Chemistry at St. Petersburg University).<br />
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He arranged the 63 elements (all that were known at that time) by increasing atomic mass, leaving gaps where he predicted that elements, that were undiscovered at that time, would fit into the table.<br />
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Mendeleev arranged is so that elements that have similar properties are in the same groups.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiA2p8kBsOuAjdzwsDHHI6-UeVXUtez41bG1PQ_JUhTIPoxY6_rjpW5z7UXGJkySed9m3htowXIxw4bY2NauBeBUVe1V1dW548K1T381bnK8tpaU8Wrea1aQvsctDL1XVxlhYGV2UCq2wPe/s1600/syllabus-2015-38-638.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="282" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiA2p8kBsOuAjdzwsDHHI6-UeVXUtez41bG1PQ_JUhTIPoxY6_rjpW5z7UXGJkySed9m3htowXIxw4bY2NauBeBUVe1V1dW548K1T381bnK8tpaU8Wrea1aQvsctDL1XVxlhYGV2UCq2wPe/s400/syllabus-2015-38-638.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">This is the Periodic Table supplied by www.cie.org.uk<br />
So this is probably the most reliable one you can find!<br />
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</tbody></table>
<b><u><span style="font-size: large;"><br /></span></u></b>
<u><span style="font-size: large;"><b>Key Terms</b></span></u><br />
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Groups = the vertical columns in the Periodic Table<br />
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Periods = the horizontal rows in the Periodic Table<br />
<b><u><span style="font-size: large;"><br /></span></u></b>
<b><u><span style="font-size: large;">Modern Periodic Table</span></u></b><br />
<b><u><span style="font-size: large;"><br /></span></u></b>
There are currently 118 known elements!<br />
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Elements are arranged by proton number in the modern Periodic Table and elements with similar priorities are still in the same groups.<br />
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<u>Groups:</u><br />
<br />
There are eight groups of elements:<br />
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<ul>
<li>Group I</li>
<li>Group II</li>
<li>Group III</li>
<li>Group VI</li>
<li>Group V</li>
<li>Group VI</li>
<li>Group VII</li>
<li>Group 0 (sometimes known as Group VIII)</li>
</ul>
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Group I is known as the alkali metals, Group II as the alkaline earth metals, Group VII as the halogens and Group 0 as the inert gases or noble gases.</div>
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The big block of elements between Groups II and III are the transition metals.</div>
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<u>Periods:</u></div>
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The periods are numbered 1-7, going down the periodic table.</div>
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Across each period the properties of the elements change:</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5cDJRvWYgU5XyB0IACm-CODY7OuOLXSsrcnEpPdEeKl-Q9vAjkUIqT6otFi1QcOUx6LZuCcdkkOooNgBUqqlK6Zprxk3vDXLXjamcKbQwSPsFfcCsZbigRGtIpIfssWN0Pc7l69YcVr0M/s1600/Screen+Shot+2016-02-07+at+20.19.51.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="170" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5cDJRvWYgU5XyB0IACm-CODY7OuOLXSsrcnEpPdEeKl-Q9vAjkUIqT6otFi1QcOUx6LZuCcdkkOooNgBUqqlK6Zprxk3vDXLXjamcKbQwSPsFfcCsZbigRGtIpIfssWN0Pc7l69YcVr0M/s400/Screen+Shot+2016-02-07+at+20.19.51.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Courtesy of Bryan Earl and Doug Wilford's <br />
Cambridge IGCSE Chemistry Third Edition<br />
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<div>
<u>Metals and non-metals:</u></div>
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<u><br /></u></div>
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The bold line that starts beneath boron divides the Periodic Table into two parts.</div>
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The elements on the left of the line are metals and the elements on the right are non-metals.</div>
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Metalloids is the name given to the elements that are on this dividing line, they are metals that have properties of both metals and non-metals.</div>
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<span style="font-size: large;"><b><u>Electronic Structure and The Periodic Table</u></b></span></div>
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<span style="font-size: large;"><b><u><br /></u></b></span></div>
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The group that an element is in determines how many electrons it has in it's outer shell.</div>
<h3>
<u style="color: red;">N.B. This does not apply to the elements in Group 0, they have either 2 or 8 electrons</u></h3>
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So the elements in Group I have 1 electron in their outer energy level and the elements in Group II have 2 electrons in their outer energy level, and so on and so on.</div>
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As you move down a group, the metallic characteristics of the elements increases, this happens because the outer energy shell becomes further away from the nucleus, as do the electrons in it. So there's less attraction between the outer energy shell's electrons and the nucleus, due to distance, so the electrons in the outer shell are easier to loose.<br />
This doesn't happen in Group VII, in this group the reactivity DECREASES as you go down the group.</div>
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Unknownnoreply@blogger.com7tag:blogger.com,1999:blog-7403964385901489143.post-83628896239552892632016-02-07T07:36:00.000-08:002016-02-07T07:42:58.534-08:00Acids and Alkalis - Basic<span style="font-size: large;"><u><b>What are acids and alkalis?</b></u></span><br />
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Acids are all: sour, corrosive and soluble in water<br />
All alkalis are the chemical opposite of acids, have a soapy feel and can remove the sharp taste from acids.<br />
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Examples of acids:<br />
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<ul>
<li>Vinegar</li>
<li>Orange juice</li>
<li>Lemons and limes</li>
</ul>
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Examples of alkalis:</div>
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<ul>
<li>Bleach</li>
<li>Toothpaste</li>
<li>Washing powder</li>
<li>Milk of magnesia</li>
</ul>
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<span style="font-size: large;"><u><b>Indicators</b></u></span></div>
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Indicators are used to test if a substance is acidic, they change colour when added to acids or alkalis. Many indicators are actually dyes that have been extracted from a natural source, e.g litmus. The table below helpfully shows some common indicators and the colours that they turn when you add them to acids or alkalis.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJ6Yp6o9PimggPKlekdNIUFjyC2Rc9GdhhvGb4ULHMTElyo_6wo1YYg9ZRPcA0K1s6G3CfkbsLymQU0A7uT4tJDYzeOvHz51RinVyER9MEKhzW93wphreSbJ0zhwfmChFPf0MmCOmGKrA7/s1600/Screen+Shot+2016-02-07+at+15.20.44.png" imageanchor="1"><img border="0" height="175" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJ6Yp6o9PimggPKlekdNIUFjyC2Rc9GdhhvGb4ULHMTElyo_6wo1YYg9ZRPcA0K1s6G3CfkbsLymQU0A7uT4tJDYzeOvHz51RinVyER9MEKhzW93wphreSbJ0zhwfmChFPf0MmCOmGKrA7/s400/Screen+Shot+2016-02-07+at+15.20.44.png" width="400" /></a></div>
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<u><b><span style="font-size: large;">Universal Indicator</span></b></u></div>
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The universal indicator is used to find out how acidic or alkaline a substance is.</div>
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It's a mix of several different indicators and it can be used as a paper or as a liquid, it turns a different colour depending on what acid or alkali is added to it. You then match up the colour of the universal indicator with something called the pH scale. </div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgSyOauqKOb3obPtXYjCHcd-yaCLECcY14W0IpKXYYL6kuxUFTkwsuqcJglIy_rdDVtaZRZWRw1NqG16Zd9f4WOBH6uMOzh14nWZwA1T6TVVb1KQ3veD98c2n5nKX5T9fRud_DjKLMVU9K4/s1600/phscale.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgSyOauqKOb3obPtXYjCHcd-yaCLECcY14W0IpKXYYL6kuxUFTkwsuqcJglIy_rdDVtaZRZWRw1NqG16Zd9f4WOBH6uMOzh14nWZwA1T6TVVb1KQ3veD98c2n5nKX5T9fRud_DjKLMVU9K4/s1600/phscale.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The pH scale.<br />
Image courtesy of https://www.chinesemedicineliving.com</td></tr>
</tbody></table>
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Each colour on the pH scale corresponds to a number, and the number tells you the pH level of the substance you're testing. For example, the pH of pure water is 7.</div>
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<u><i>What the pH level tells you about a substance</i></u></div>
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<ul>
<li>pH of less than 7 - acid</li>
<li>pH of 7 - neutral</li>
<li>pH of more than 7 - alkaline</li>
</ul>
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjna4GPXZ-PgdZ1wCqN6g6fmAsAUHSnW5PLiRawHwrvsvgUIusCquxEp_QBgsSn3J3F5ZmO1abD77IxLLMb3Y9-408LVDFwWEhJj4VR6foWZRj1goKYwddDo83WlYxWlI5INxpJ1GRE6NKC/s1600/127745_RB_02_FB.EPS_1000.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjna4GPXZ-PgdZ1wCqN6g6fmAsAUHSnW5PLiRawHwrvsvgUIusCquxEp_QBgsSn3J3F5ZmO1abD77IxLLMb3Y9-408LVDFwWEhJj4VR6foWZRj1goKYwddDo83WlYxWlI5INxpJ1GRE6NKC/s200/127745_RB_02_FB.EPS_1000.jpg" width="200" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">pH meter<br />
Image courtesy of http://www.conrad-electronic.co.uk</td></tr>
</tbody></table>
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Another method of measuring the pH of a substance is to use a pH meter. </div>
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When you place the electrode into the solution, the electronic display shows the pH level.</div>
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<u><b><span style="font-size: large;"><br /></span></b></u></div>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-7403964385901489143.post-87987915659469129812016-01-14T04:03:00.000-08:002016-01-14T04:03:53.238-08:00Thermal Capacity<b style="color: #666666; font-family: Verdana, sans-serif; font-size: 15px;"><i><u><span style="font-size: large;">Physics -</span><span style="font-size: medium;"> Thermal capacity</span></u></i></b><br />
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<span style="background-color: white;"><span style="color: #666666; font-family: Verdana, sans-serif;"><span style="font-size: 15px;"> Thermal capacity is how much heat is required to raise the temperature of a body by 1</span></span></span><span style="background-color: white; color: #666666; font-family: Verdana, sans-serif; font-size: 15px;">℃.</span><br />
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<span style="background-color: white; color: #666666; font-family: Verdana, sans-serif; font-size: 15px;">It's measured in joules per </span><span style="background-color: white; color: #666666; font-family: Verdana, sans-serif; font-size: 15px;">℃, J/</span><span style="background-color: white; color: #666666; font-family: Verdana, sans-serif; font-size: 15px;">℃.</span><br />
<b style="color: #666666; font-family: Verdana, sans-serif; font-size: 15px;"><i><u><span style="font-size: medium;"><br /></span></u></i></b>
<b style="color: #666666; font-family: Verdana, sans-serif; font-size: 15px;"><i><u><span style="font-size: medium;">Equation</span></u></i></b><br />
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<span style="color: #666666; font-family: Verdana, sans-serif;"><span style="background-color: white;"><span style="font-size: 15px;">thermal capacity = mass </span></span><span style="font-size: 15px;">× specific heat capacity </span></span></div>
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<span style="color: #666666; font-family: Verdana, sans-serif;"><span style="font-size: 15px;">or thermal capacity </span></span><span style="background-color: white; color: #666666; font-family: Verdana, sans-serif; font-size: 15px;">=</span><span style="color: #666666; font-family: Verdana, sans-serif; font-size: 15px;"> m × c</span></div>
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<span style="color: #666666; font-family: Verdana, sans-serif; font-size: 15px;"><br /></span></div>
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<span style="color: #666666; font-family: Verdana, sans-serif; font-size: 15px;">Note: c is the symbol for specific heat capacity</span></div>
Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-7403964385901489143.post-28229147625271073432016-01-13T07:12:00.000-08:002016-01-13T07:12:18.932-08:00Thermometers <span style="color: #666666; font-family: Verdana, sans-serif;"><b><i><u><span style="font-size: x-large;">Physics -</span><span style="font-size: large;"> Thermometers: liquid-in-glass</span></u></i></b></span><br />
<b><i><u><span style="color: #666666; font-family: Verdana, sans-serif; font-size: large;"><br /></span></u></i></b>
<u><span style="color: #666666; font-family: Verdana, sans-serif;">Key Terms:</span></u><br />
<u><span style="color: #666666; font-family: Verdana, sans-serif;"><br /></span></u>
<span style="color: #666666; font-family: Verdana, sans-serif;">Capillary tube - A glass tube with thick walls and a narrow interior hollow tube (bore). It has a bulb at one end. </span><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgj7gLbGjbf69bUgIuebci_1Xv6DB67O8OZgGcJEZxfX6eWWeYw7iwsh8EHhQaOE-LsvBoCbRKIOIkPJFUAaEnaL-OMciyUedqOu9MyGdyu_oymDt4mV_zEu4KbW3e736A0y8J2g8QEsPYT/s1600/images.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><span style="color: #666666; font-family: Verdana, sans-serif;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgj7gLbGjbf69bUgIuebci_1Xv6DB67O8OZgGcJEZxfX6eWWeYw7iwsh8EHhQaOE-LsvBoCbRKIOIkPJFUAaEnaL-OMciyUedqOu9MyGdyu_oymDt4mV_zEu4KbW3e736A0y8J2g8QEsPYT/s1600/images.png" /></span></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="color: #666666; font-family: Verdana, sans-serif;">Image source and credit: http://www.advancedaquarist.com</span></td></tr>
</tbody></table>
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<span style="color: #666666; font-family: Verdana, sans-serif;">To the left is a labelled diagram of a thermometer, you don't need to know all of the different parts of a thermometer, but I included it to help you understand.</span><br />
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<u><span style="color: #666666; font-family: Verdana, sans-serif;">How they work:</span></u><br />
<u><span style="color: #666666; font-family: Verdana, sans-serif;"><br /></span></u>
<span style="color: #666666; font-family: Verdana, sans-serif;">When the glass bulb is is heated, the liquid in the bulb starts to expand up the capillary tube. </span><br />
<u><span style="color: #666666; font-family: Verdana, sans-serif;"><br /></span></u>
<span style="color: #666666; font-family: Verdana, sans-serif;">The liquid must have the following properties:</span><br />
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<ul>
<li><span style="color: #666666; font-family: Verdana, sans-serif;">Be able to be seen easily</span></li>
<li><span style="color: #666666; font-family: Verdana, sans-serif;">Be able to expand and contract quickly over a wide range of temperatures</span></li>
<li><span style="color: #666666; font-family: Verdana, sans-serif;">Not stick to the inside of the capillary tube</span></li>
</ul>
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<span style="color: #666666; font-family: Verdana, sans-serif;">Commonly Mercury and Alcohol (coloured) are used because Mercury boils at 357<span style="background-color: white;">℃ and freezes at -39</span><span style="background-color: white;">℃. Alcohol boils at 78</span><span style="background-color: white;">℃ and freezes at -115</span><span style="background-color: white;">℃, therefore Alcohol is more suited to low temperatures and Mercury is suitable for higher temperatures.</span></span></div>
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<b><i><u><span style="color: #666666; font-family: Verdana, sans-serif; font-size: large;">Clinical Thermometers</span></u></i></b></div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWqFXYIKle1yvCbX0e85010q7tDHfL_Ry9HacZ161OQ7sY9nPN6VGvGOvhp5-YR-JOmJrP63GtkgctCKMYwOmf8JqsLu9EVJXmTcje9zQTTtpNG9aNg9lEjnIFNIzDhawxTVoEVP56CmNA/s1600/thermometer-medical-clinical-thermometer-temperature.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="160" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWqFXYIKle1yvCbX0e85010q7tDHfL_Ry9HacZ161OQ7sY9nPN6VGvGOvhp5-YR-JOmJrP63GtkgctCKMYwOmf8JqsLu9EVJXmTcje9zQTTtpNG9aNg9lEjnIFNIzDhawxTVoEVP56CmNA/s320/thermometer-medical-clinical-thermometer-temperature.png" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Image source and credit: http://www.http://www.pd4pic.com</td></tr>
</tbody></table>
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<span style="color: #666666; font-family: Verdana, sans-serif;">Clinical thermometers are used by doctors and nurses to measure patient's body temperatures, they are mercury-in-glass thermometers. </span></div>
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<span style="color: #666666; font-family: Verdana, sans-serif;">These are different from normal mercury-in-glass thermometers as their scale only extends for a few degrees either side of 37<span style="background-color: white;">℃, this is because 37</span></span><span style="background-color: white;"><span style="color: #666666; font-family: Verdana, sans-serif;">℃ is the normal body temperature. </span></span></div>
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<span style="background-color: white;"><span style="color: #666666; font-family: Verdana, sans-serif;">The capillary tube in these thermometers is very narrow, allowing for a very accurate reading to be taken, a.k.a </span></span><span style="color: #666666; font-family: Verdana, sans-serif;">the thermometer has a high sensitivity.</span></div>
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<u><span style="color: #666666; font-family: Verdana, sans-serif;">How they work:</span></u></div>
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<span style="color: #666666; font-family: Verdana, sans-serif;">The capillary tube has a constriction (check diagram above if you don't know what this is) just above bulb.</span><br />
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<span style="color: #666666; font-family: Verdana, sans-serif;">The thermometer is placed under the tongue and kept there for 1 minute, the mercury expands it heats up and forces past the constriction. Once the thermometer is removed from the mouth, the mercury in the bulb cools and contracts, breaking off from the mercury thread at the constriction, but the mercury that's beyond the constriction stays in the tube, showing the body temperature is at. </span><br />
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<span style="color: #666666; font-family: Verdana, sans-serif;">By flicking your wrist, the mercury returns to the bulb again.</span><br />
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<span style="color: #666666; font-family: Verdana, sans-serif;">Mercury thermometers (for clinical use) are now being replaced by digital thermometers, because mercury is toxic.</span><br />
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<b><i><u><span style="color: #666666; font-family: Verdana, sans-serif; font-size: large;">Thermocouple Thermometers</span></u></i></b><br />
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<span style="color: #666666; font-family: Verdana, sans-serif;">Thermocouples are used to measure temperatures that change quickly or are very high.</span><br />
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<span style="color: #666666; font-family: Verdana, sans-serif;">Thermocouple thermometers have wires made of two different materials, e.g iron and copper that are joined together. If one junction is at a higher temperature than the other one, an electric current flows, producing a reading on a digital voltmeter, the voltage of the current is directly related to the temperature.</span><br />
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<span style="color: #666666;"><span style="font-family: Verdana, sans-serif;">They are used in industry to measure a vast range of temperatures from -250</span><span style="background-color: white; font-family: Verdana, sans-serif;">℃ to 1500</span></span><span style="background-color: white; color: #666666; font-family: Verdana, sans-serif;">℃, they are also very good at measuring the temperatures on small objects or for rapidly changing temperatures.</span><br />
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<b><i><u><span style="color: #666666; font-family: Verdana, sans-serif; font-size: large;">Resistance Thermometers</span></u></i></b><br />
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<span style="color: #666666; font-family: Verdana, sans-serif;">Resistance thermometers are used to measure temperatures accurately from -200</span><span style="background-color: white; color: #666666; font-family: Verdana, sans-serif;">℃ to 1200</span><span style="background-color: white; color: #666666; font-family: Verdana, sans-serif;">℃.</span><br />
<span style="background-color: white;"><span style="color: #666666; font-family: Verdana, sans-serif;">They work by using the fact that electrical resistance builds up in a platinum wire when the temperature increases. </span></span><br />
<span style="background-color: white;"><span style="color: #666666; font-family: Verdana, sans-serif;">They are best used for steady temperatures and are bulky.</span></span><br />
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<b><i><u><span style="color: #666666; font-family: Verdana, sans-serif; font-size: large;">Constant-Volume Gas Thermometers</span></u></i></b><br />
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<span style="color: #666666; font-family: Verdana, sans-serif;">Constant-Volume Gas thermometers use the change in pressure of a gas to measure temperature. </span><br />
<span style="color: #666666; font-family: Verdana, sans-serif;">It works over a wide rang of temperatures, and is bulky.</span><br />
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<b><i><u><span style="color: #666666; font-family: Verdana, sans-serif; font-size: large;">Thermistors</span></u></i></b><br />
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<span style="color: #666666; font-family: Verdana, sans-serif;">Thermistors work over a small range, ie. -5</span><span style="background-color: white; color: #666666; font-family: Verdana, sans-serif;">℃ to 70</span><span style="background-color: white;"><span style="color: #666666; font-family: Verdana, sans-serif;">℃. It's resistance decreases </span></span><span style="color: #666666; font-family: Verdana, sans-serif;">with temperature.</span><br />
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<b><i><u><span style="color: #666666; font-family: Verdana, sans-serif; font-size: large;">Thermochromic Liquids</span></u></i></b><br />
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<span style="color: #666666; font-family: Verdana, sans-serif;">Thermochromic liquids change colour when heated or cooled, they have a limited range of temperatures (around room temperatures).</span><br />
<br />Unknownnoreply@blogger.com2tag:blogger.com,1999:blog-7403964385901489143.post-7355313072747789402016-01-12T07:44:00.002-08:002016-01-12T08:32:23.779-08:00Linear Expansivity<div>
<span style="font-size: large;"><b><i><u>Definition</u></i></b></span></div>
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Linear expansivity is the increase of 1m of material in size for a 1℃ rise in temperature.</div>
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When designing bridges, railway tracks and copper piping etc. engineers have to allow for linear expansivity.<br />
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Linear expansivity is the amount by which a material increases in size due to an increase in temperature. It's measured in meters per degree Celsius. It's symbol is the greek symbol for alpha, α.<br />
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To calculate the linear expansion of something, you need to know the following:<br />
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<ul>
<li>The length of the bridge</li>
<li>The range of temperatures it will experience</li>
<li>The linear expansivity of the material that's going to be used</li>
</ul>
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The linear expansivity of materials is found through experimenting. </div>
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Steel's linear expansivity is 0.000 012m per ℃, so 1m will become 1.000 012m if the temperature increases by 1℃.</div>
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<b><i><u><span style="font-size: large;">Equation</span></u></i></b></div>
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expansion = linear expansivity ⨉ original length ⨉ temperature rise </div>
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<b><i><u><span style="font-size: large;">Example question and working</span></u></i></b></div>
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Question:<i> How long will a 100m long steel bridge become if the temperature increases by 60℃</i>? <i>Note that the linear expansivity of steel is 0.000 012m.</i></div>
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Answer: The bridge would expand by 0.000 012m ⨉ 100m if the temperature rose by 1℃. So if the temperature rises by 60℃, then the bridge would expand by </div>
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0.000 012m ⨉ 100m ⨉ 60℃ = 0.072m or 7.2cm</div>
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<b><i><u><span style="font-size: large;">Change in length </span></u></i></b></div>
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Delta (the greek letter) often means the change in a quantity or the difference. So the change in temperature in the above question is 60℃ and the change in length is 7.2cm.</div>
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You need to remember the following symbols:</div>
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Delta: </div>
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Change in length:</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxUcfrn1AipmX4BmECwncMml5UCfdgSsOOTRyMaC_N7Ztb2V0DOq-Ewc0D-I2_vT7SYW_aGHtBUnGEz4dc1WYtnWwqYOgb0xIf-M9p2yTj6E29v-Z3fbF40oQXfhdM8BewxlIihmiP11Ez/s1600/Screen+Shot+2016-01-12+at+15.37.44.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxUcfrn1AipmX4BmECwncMml5UCfdgSsOOTRyMaC_N7Ztb2V0DOq-Ewc0D-I2_vT7SYW_aGHtBUnGEz4dc1WYtnWwqYOgb0xIf-M9p2yTj6E29v-Z3fbF40oQXfhdM8BewxlIihmiP11Ez/s1600/Screen+Shot+2016-01-12+at+15.37.44.png" /></a></div>
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Change in temperature:</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiA_wCkw2JmuhbIpvWIMINlfZkP7BzfOxxpCe8OOotr8_D9h0bHXL-0kXlQRZYKFSjVMeDLacW9f5bTP5Hf-HM_exFpVlf8NCEoQ4FcF4Qtfr8fbp3T-CXyI_GHQP94sJOHsC5OdHkDDo5j/s1600/Screen+Shot+2016-01-12+at+15.39.31.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiA_wCkw2JmuhbIpvWIMINlfZkP7BzfOxxpCe8OOotr8_D9h0bHXL-0kXlQRZYKFSjVMeDLacW9f5bTP5Hf-HM_exFpVlf8NCEoQ4FcF4Qtfr8fbp3T-CXyI_GHQP94sJOHsC5OdHkDDo5j/s1600/Screen+Shot+2016-01-12+at+15.39.31.png" /></a></div>
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<span style="font-size: large;"><b><i><u><br /></u></i></b></span></div>
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-7403964385901489143.post-11102169458076337002016-01-12T06:17:00.000-08:002016-01-12T07:14:09.346-08:00Boyle's Law<br />
You might think that Boyle's law is complicated, but it really isn't!<br />
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Boyle's law states: The pressure and volume of a gas have an inverse relationship, when temperature is held constant.<br />
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This means that if you take a container filled with a gas, and halve the size of the container, then the pressure will be doubled (because there will be twice as many collisions per second).<br />
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<br />Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-7403964385901489143.post-7901236689473171742016-01-12T05:23:00.000-08:002016-01-12T05:23:46.048-08:00The Classification System<div style="color: #616161; font-family: arial, sans-serif;">
<u><span style="font-size: large;">The Key Terms Explained:</span></u></div>
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<span style="color: #38761d;">Kingdom</span> - There are 5 different kingdoms</div>
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<li>the animal kingdom (all multicellular animals)</li>
<li>the plant kingdom (all green plants)</li>
<li>the fungi kingdom (e.g. mushrooms, moulds and yeast)</li>
<li><span style="color: #666666;"><span style="font-family: Arial, Helvetica, freesans, sans-serif;">the prokaryote kingdom (e.g. blue-green algae and bacteria)</span></span></li>
<li><span style="color: #666666;"><span style="font-family: Arial, Helvetica, freesans, sans-serif;">the </span></span><span style="font-family: Arial, Helvetica, freesans, sans-serif;"><span style="color: #666666;">protoctists kingdom (e.g. </span></span><span style="color: #666666;"><span style="font-family: Arial, Helvetica, freesans, sans-serif;"><span style="border: 0px; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Plasmodium,</span> </span><span style="border: 0px; font-family: Arial, Helvetica, freesans, sans-serif; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Chlorella</span><span style="font-family: Arial, Helvetica, freesans, sans-serif;"> and <span style="border: 0px; line-height: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Amoeba)</span></span></span></li>
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<span style="color: #38761d;">Genus - </span><span style="color: #666666;">A group of closely related species.</span></div>
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<span style="color: #38761d;">Species - </span><span style="color: #666666;">A group of closely related organisms that can breed to produce fertile offspring. The smallest group of organisms.</span></div>
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<span style="color: #38761d;">Binomial system -</span><span style="color: #38761d;"> </span><span style="color: #666666;">An internationally agreed system used to name organisms scientifically, it uses the latin name of the genus and species they belong to, e.g. </span></div>
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<a href="https://sites.google.com/site/landervillescience/biology/classification-systems/Screen%20Shot%202016-01-12%20at%2012.32.03.png?attredirects=0" imageanchor="1" style="background-image: none; background-position: initial initial; background-repeat: initial initial; border-bottom-style: none; color: #835ea5; cursor: text; text-decoration: none;"><img border="0" src="https://sites.google.com/site/landervillescience/biology/classification-systems/Screen%20Shot%202016-01-12%20at%2012.32.03.png" style="border-bottom-left-radius: 2px; border-bottom-right-radius: 2px; border-top-left-radius: 2px; border-top-right-radius: 2px; border: none; margin: 7px; padding: 0px;" /></a></div>
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The binomial system is also known as "Binomial nomenclature". Binomial means "two names", the first name always gives the genus and is always spelt with a capital letter at the start, the second always gives the species and is always spelt with a small letter at the start. </div>
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<span style="color: #38761d;">Morphology - </span><span style="color: #666666;">The study of an organism's exterior, their 'outer appearance'.</span></div>
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<span style="color: #38761d;">Anatomy - </span><span style="color: #666666;">The study of an organism's internal structure (you have to direct the organism to study this).</span></div>
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<span style="color: #38761d; font-family: arial, sans-serif; font-size: 14px;">Cladistics -</span><span style="color: #38761d; font-family: arial, sans-serif; font-size: 14px;"> </span><span style="color: #666666;"><span style="font-family: arial, sans-serif;"><span style="font-size: 14px;">The biological classification process, that involves organisms being grouped together according to whether or not they have one or more shared unique characteristics derived from the group's last common ancestor, which are not present in more distant </span></span></span><span style="color: #666666; font-family: arial, sans-serif;"><span style="font-size: 14px;">ancestors. </span></span></div>
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<span style="font-size: large;"><i><u>Why do we classify organisms?</u></i></span></div>
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<ul>
<li>By classifying organisms it is possible to determine which are most at risk from extinction.</li>
<li>We can gain a better understanding of evolutionary relationships.</li>
</ul>
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<u><i><span style="font-size: large;">The use of DNA in classification</span></i></u></div>
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Each species has a certain number of chromosomes and sequence of bases in it's DNA that's unique to that species. This makes it distinguishable from other species, and can help if several different species are very similar anatomically and morphologically. </div>
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