heat energy

grade eight physics

Continuing the science blocks at East Bay Waldorf school, I am teaching physics for grade eight. Physics in the upper grades begins in grade six, and continues on as a sequence of advancing concepts through grade eight. In grade eight, the concepts covered are thermal dynamics, refraction, hydraulics, and electromagnetism.

Our first week of physics, we learned about heat energy. Heat energy travels via radiation, conduction, and convection. I organized our week according to these three principles. The approach to physics in Waldorf is phenomena-based, meaning, the instruction is designed to be experiential, and not abstracted through lecture or texts. Through direct experience and observations of demonstrations, the children live in the phenomena of physics.

The beauty of physics is that, unlike learning about Renaissance art, or the American Revolution, physics is experienced in the everyday. The physics block can be regarded as a way of simply giving a vocabulary and elucidation of what the children already know and experience.


Day One: Heat Experienced in the Everyday, and Radiation

On our first day, I had the students write a paragraph on their experience of how heat and cold are experienced in their everyday lives. It was a way for them to give thought to their actions and their feelings as they wake in the morning and feel the coldness of a bare floor, the warmth from a robe or a cup of hot chocolate. They become active in feeling warmth in standing close to their friends, and the sun as it filters into the classroom space.

In observing the effects of the sun on dark and light materials, and in experiencing the heat from a radiant heater, the students learned about RADIATION, the transfer of heat energy through space. The key observations were that dark objects tend to absorb heat, while lighter objects tend to reflect heat.



Day Two: Conduction

The rhythm of the main lesson is such that the students are engaged in some movement exercises and mental acitivities to synchronize the class as a whole, followed by a review of material introduced the day before, then the new material, and work in their main lesson books.

In day two, I had the students form two lines and, joining hands, formed a wave. Good for their physical beings, and also had demonstrated for them how radiated heat travels (through waves).

We observed the phenomena of CONDUCTION. I used a heating plate with a baking stone set on top, and placed various materials on top of that: a piece of marble, a metal cup, cork, rubber stopper, a beaker of water, a shell, wood block. The students touched the materials after the baking stone had heated, and also after the heat was turned off.

Conduction is the transfer of heat energy between materials that are in direct contact with each other. We witnessed that different materials behave differently to applied heat: the metal cup seemed to have heated up the fastest, the marble heated to the highest temperature, and the marble also retained the heat the longest.

Day Three: Convection, Part I

Our movement exercise included two lines of students who demonstrated the wave, and they also passed a ball from one person to the next, showing that "direct contact" is required for conduction. Each line of students raced one another - let's see who can conduct heat the fastest!

The phenomena demonstrated on day three was CONVECTION, the transfer of heat energy through air or liquid by a moving current. I demonstrated for them how heat from a candle produces a current of warmed air that rises. This rising heat can be used to do work - thermal dynamics. I showed them how to make tiny pinwheels that balance on bent paper clips. They held their pinwheels over the candle, and the pinwheels turned!

Day Four: Convection, Part II

We continued the concept of convection. This time, using a large glass container, I showed them how a red dye placed at the bottom of the water-filled jar would begin to move towards a corner that was being heated by a candle. It showed how heated liquid rises, and as the water cools with an ice cube placed at the opposite end, the cooled water sinks, creating a convection current.

In their main lesson books (MLBs), the students would write a paragraph and draw a picture that would help them synthesize their learning. Following a two-day rhythm, the material that I introduced one day would be become their MLB work the following day.

Day Five: Designing an Eco-Friendly Home

The knowledge gleaned from the week's work is connected with practical application. In designing homes that are energy-efficient, and eco-friendly, which is a growing industry, knowing how to regulate temperature of a home with efficiency and with resource conservation is very important to the comfort of its occupants. I put the students in small groups and gave them the following exercise: they are an architectural firm who a client is asking to design an energy efficient home that uses heat energy wisely, so innovative use of materials and design elements is essential in winning the bid. The students took the exercise whole-heartedly and came up with some creative solutions such as grass rooves, rain catchment systems, gray water, radiant-heated floors, solar energy, wind energy, and use of materials that have good thermal retention and are eco-friendly.

To keep things fun, and help them with remembering concepts and terms, I had them draw little cartoons associated with the concepts. With radiation, they drew a surfer enjoying heat from the sun, saying "Radical, dude!" With conduction, they drew a duck whose feet are in direct contact with an icy pond, "Quack, my feet are cold!" With convection, they drew a conveyor belt, where heat was actually being moved from one place to another, "More heat, coming right up!"