Phase changes of water - Oakland Schools
Phase changes of water - Oakland Schools
Phase changes of water - Oakland Schools
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Assessment:<br />
Have students pair and share to discuss the results <strong>of</strong> the demonstration. Their<br />
discussion should include the concepts <strong>of</strong> conduction, convection, density, and heat<br />
transfer.<br />
Explanation for teacher:<br />
Warm <strong>water</strong> is more buoyant than cold <strong>water</strong>. Since warm <strong>water</strong> is below the ice and<br />
cold <strong>water</strong> in Beaker B, the warm <strong>water</strong> rises, whereas the cold <strong>water</strong> sinks. This is<br />
convection in action!<br />
In Beaker A, on the other hand, the warm buoyant <strong>water</strong> overlays the cold ice. This is a<br />
very stable arrangement, and convection does not occur. Heat transfer only occurs<br />
through conduction in this case.<br />
In fluids, such as <strong>water</strong> and air, convection is a much more efficient method <strong>of</strong> heat<br />
transfer than conduction. This difference in efficiency produced the dramatic difference<br />
in the time required to melt the ice. Although conduction was at work in both cases, it<br />
transferred much less heat than convection.<br />
23
Change language