Conduction of heat

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0 height="100%"><tr> <td valign="top" width=200 BGCOLOR="#003333" TEXT="#F7F7FF" background="03fd4c00dduajq.gif"> <div> <TABLE BORDER="0" CELLPADDING="2" CELLSPACING="0" WIDTH="95" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP HEIGHT= 46 WIDTH="91"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="46" ALIGN="bottom" WIDTH="91" HSPACE="0" VSPACE="0"></tD> </tR> </TABLE></div> <div> <A HREF="index.htm" TARGET="_top" TITLE="Science For All"><U>home</U></A></div> <div> <A HREF="site_map_and_site_search_engine.htm" TARGET="_top" TITLE="Science for all site map"><U>Site map + site search engine</U></A></div> <bR> <div> <A HREF="slg.htm" TARGET="_top" TITLE="solids, liquids and gases"><U>solids, liquids and gases</U></A></div> <div> <A HREF="slg_structure.htm" TARGET="_top" TITLE="Solids, liquids and gases their molecul"><U>Solids, liquids and gases - their 'molecular' structure</U></A></div> <div> <A HREF="id63.htm" TARGET="_top" TITLE="Changes of state"><U>Changes of state</U></A></div> <div> <A HREF="id69.htm" TARGET="_top" TITLE="Air resistance"><U>Air resistance</U></A></div> <div> <A HREF="id79.htm" TARGET="_top" TITLE="Mass and weight"><U>Mass and weight</U></A></div> <div> <B><IMG BORDER="0" SRC="Symb075c00b700c8ffffff00.gif" HEIGHT="13" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">Conduction of heat</B></div> <div> <A HREF="id92.htm" TARGET="_top" TITLE="Static Electricity"><U>Static Electricity</U></A></div> <bR> </td> <td valign="top" BGCOLOR="#FFFFFF" TEXT="#080000" bgproperties="fixed" background="0f8a0a03.gif"> <div> Conduction of heat</div> <bR> <div> You are visiting the Science For All site</div> <div> <B><IMG SRC="0f7f4040.gif" border=0 width="500" height="4" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <bR> <div> Before you start, make sure that you know about the <A HREF="slg_structure_solids.htm" TARGET="_top" TITLE="Solids, liquids and gases their molecul"><U>arrangement of particles in a the three states of matter.</U></A></div> <bR> <bR> <div> When you leave a spoon in a cup of hot drink, the bit poking out of the drink gets hot. Why? Conduction! That's the easy bit - you probably know that is the way that heat travels through a solid. But how does conduction actually work? Hopefully, by the end of this short page, you will know and be able to explain it to someone else.</div> <bR> <div> Metals are the best conductors of heat. This is because the atoms of metals are very closely packed together.</div> <bR> <div> <IMG SRC="1d066710.gif" border=0 width="358" height="113" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> When you heat atoms, they start to vibrate more. So, if you heat the 3 atoms at the left hand end of the piece of metal in the diagram above, they wil vibrate more. This is shown below (orange shows the atoms that are vibrating more):</div> <bR> <div> <IMG SRC="1d166710.gif" border=0 width="358" height="113" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> As these vibrate more, they bang into the ones next to them. This makes these atoms vibrate more than they were at first. </div> <bR> <div> <IMG SRC="1d266710.gif" border=0 width="358" height="113" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> Then these atoms bang into their neighbours, making them vibrate more ... and so on. Eventually all of the particles are vibrating faster and so the whole piece of metal is hotter than at the start.</div> <bR> <div> Question. </div> <div> Which parts of the piece of metal will be hotter and why?</div> <bR> <div> <A HREF="id86.htm" TARGET="_top" TITLE="Temperature of metal question answer."><U><IMG SRC="1be373d0.gif" border=0 width="55" height="61" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A> Click on the apple to reveal the answer</div> <bR> <div> In liquids and gases, the particles are not fixed in place so this effect does not happen. </div> <bR> <div> Higher levels:</div> <div> Metals are particularly good conductors of heat because their particles are very closely packed so the vibrations are passed on very quickly. They also contain large numbers of <FONT SIZE="4" COLOR="#FF0000" FACE="Arial" >"free electrons"</FONT>. These drift slowly through the structure, giving metals their strength and other properties. As the metal is heated, the free electrons closest to the heat source  are heated. This makes them move faster and they travel through the metal, colliding with both atoms and other electrons. This naturally makes these vibrate faster (or move through the metal faster - in the case of collisions with other free electrons). Thus the heat is passed quickly through the metal.</div> </td> </tr></table></body>