Convection can't occur in solids (you'll see why in a moment). It is the way that heat travels through liquids and gases though.
|Here we see a purple potassium permanganate crystal
being heated in a flask of water. As it dissolves to form
a purple dye, a plume of dye rises upwards. When it
reaches the surface it is pushed over by the dye rising
underneath. This is caused by CONVECTION
and the flow of water shown by the dye is called a CONVECTION CURRENT.
As the water particles are heated, they gain more energy and move further apart. Where this has happened the water is now less dense. Lower density substances float on higher density ones so the heated (less dense) water rises up - CONVECTION.
You can now see why convection can't occur in solids (I hope !). Convection occurs when higher energy particles MOVE, taking the heat energy with them. Since in solids the particles can't move, convection can't happen. In gases, the particles can move though; in fact only too well, so perhaps we might expect convection to occur even more easily in gases than in liquids ?
|In this photo, the shimmering of telegraph poles is
not because the photographer's hand was shaking. In fact
it is caused by CONVECTION.
As the hot road heats up the air next to it, the air
rises by convection and creates the effect - you can see
a similar effect above a hot radiator in a classroom.
It isn't water on the road by the way; it's a MIRAGE. That's caused by convection too. A bit of research might help you find out how mirages need convection !
|This cloud is known as a hammerhead or anvil for fairly obvious reasons. Another result of convection. Like mirages mentioned above, as the hot ground heats up, the air above it rises. It continues to do so until at altitude, water vapour in the rising air column condenses out as tiny water droplets - that's what we see as a cloud.|
Don't believe all you read !
|Whoever named "radiators"
wasn't doing their job very well. In fact radiators warm
a room up by CONVECTION
much more than by radiation. The hot radiator warms up a
layer of air next to it. The warmed air rises by
convection, setting up a convection
current which takes warm air around the
The heat from the radiator is provided by the hot water circulating through it. How does the heat from the hot water get out to warm the air though ?
|First try the activities for this section -
. . . then go on to the next section.