Summary
Through a teacher demonstration using water, heat and food coloring, students see how convection moves the energy of the Sun from its core outwards. Students learn about the three different modes of heat transfer—convection, conduction, radiation—and how they are related to the Sun and life on our planet. Includes a student worksheet for data collection and graphing.
This engineering curriculum meets Next Generation Science Standards (NGSS).
Engineering Connection
Engineers design measuring devices to record changes in density and temperature on the Sun. By observing the Sun we can learn about what is happening under the surface and how heat is moving through the Sun. Heat transfer also occurs on Earth and engineers need to understand the different modes in order to build devices and structures that do not overheat or get too cold.
Pre-Req Knowledge
Familiarity with the Sun's composition, layers and importance as Earth's energy source, as provided in the Blazing Gas lesson of this Solar System unit.
Learning Objectives
After this activity, students should be able to:
Define the three different modes of heat transfer.
Explain how heat gets from the Sun to Earth.
Give one example of why engineers need to understand heat transfer.
Introduction/Motivation
Can heat move? Of course it can. Heat (energy) travels in three ways: convention, conduction and radiation. Conduction works by direct contact of two materials. This is what happens when a pot is placed on the stove. First the stove material is heated. Then the heat is transferred by conduction to the pot, which is in direct contact with the hot stove. Convection works through the interaction of fluid molecules such as air or water. Convection typically occurs when a hot fluid or gas moves upward. Radiation works through the movement of heat waves. This is similar to light and radio waves.
So, how does heat get from the Sun to Earth? Conduction and convection require a material (either solid, liquid or gas) to be present. (Emphasize: Since there is no matter in space between the Sun and Earth, all the heat from the Sun comes to us in the form of radiation.) Inside the Sun is matter and therefore other forms of heat transfer are at work. The Sun uses two methods to transport energy out from the interior. The first is radiation. Radiation begins in the Sun's core. In the Sun's radiation zone, heat from the core travels as electromagnetic waves (radiation) outwards to the Sun's convective zone. Convection currents are currents created when there are differences in temperature and density. (Emphasize: Warmer liquids and gasses are less dense and therefore float (or rise) when in cooler liquids and gasses.) ) As this warmer gas (or liquid) rises, cooler gas (or liquid) moves to take its place where it is heated. This is called a convection current. Convection currents swirl the energy until it passes through to the Sun's photosphere.