Convection Lesson 2

Objectives

• Observe two demonstrations showing convection in a beaker and a large tank of water.

• Be able to describe weather systems in terms of the movement and changing density of regions of air undergoing heating and cooling.

Task 1

Last lesson you investigated how convection affected the cooling of water in a beaker.  This lesson builds on these ideas to explain how weather systems work.

Watch as your teacher demonstrates convection taking place in a beaker of water, using potassium permanganate crystals to dye the water in order to observe it moving as it undergoes heating and cooling.

Task 3

Sort the sentence fragments below into the correct order to explain the process of convection.  When you have finished, get your teacher to check they are correct and then stick them into your book.

Heat is transferred in fluids by convection. As the

dense, sinks to replace it. We call this            warm fluid expand. These

cooler fluid, which is more                    fluid is heated, regions of

movement of fluid a “convection current”.

less dense and “float” upward. Regions of

regions of warm fluid are

Task 4

Now your teacher will show you convection currents in a tank of water, using blue ice cubes to show the cold water sinking and hot water with red food dye to show the warm water rising.  Watch closely and think about how this compares to the breezes you notice by the coast.

You can also see a simple video of something similar below:

Homework

Using the concepts your teacher explained and the observations you made when watching the demonstration, put the cards in the correct places on the diagram to explain how convection currents generate weather systems at the coast.