Smoke Box Demonstration
MATERIALS:
Small glass box with two chimneys
Votive candle
Match
Firework punk
EXPLORE:
A lit candle is placed under one chimney in the box. The teacher will strike a match and light the punk with it.
1. You may smell smoke or sulfur from the extinguished match. What are some explanations for how the odor travelled across the room? Try to think of two reasonable possibilities.
The room has wind in it, because of the air conditioner. The wind/air conditioner could blow the smoke smell all over the room.
The smoke particles, being gases, would try to diffuse across the room to equalize. This could be why I can smell them.
2. Observe what happens as the teacher holds a lit fireworks punk over the box. Record your observations here. The smoke flows down into the chimney, as heat exits the other chimney.
3. Use this space to draw the box and demonstration you have just observed.
CONCEPT INVENTION:
Answer the following questions to help you understand the purpose of this demonstration.
1. What was the purpose of the lit candle? The candle provided heat to drive the convection cycle.
2. Why was the lit candle place directly under one of the chimneys? The candle was placed directly under one chimney so that the heated air particles had a direct pathway out of the box, in order to create the best draft into the box on the other side, possible.
3. Imagine that you were holding the palm of your hand 10 cm above the candle-side chimney. Would you feel heat, wind, neither, or both? How do you know, even though you didn’t actually hold your hand there? Heat rises, and there’s a candle flame of hot air being funneled up a narrow chimney. I am certain that I would feel the heat, and I would feel the air flow, or wind, that is carrying it.
TERM INTRODUCTION:
Vect- to carry (Greek)
Con- together, with (Italian)
1. Look back at your drawing of the box model. Label the drawing “Convection Box.” Use the information above to explain why convection is a good term to apply to this type of air movement. As hot air is flowing from the box on one side, it is carrying the smoke-filled air into the box on the other side.
2. On the convection box drawing, write additional labels to signal where the smoke was drawn into the box and where the smoke exited the box.
3. As the candle heated air particles, what happened to their kinetic energy? What does the candle represent in the natural world? The kinetic energy of the air particles increases as the particles are heated.
4. As air particles got farther apart and some went out the exit chimney, what happened to the amount of pressure the air was able to exert inside the box? As the particles of air get farther apart, their air pressure decreases.
APPLICATION:
1. Bernoulli’s principle is a scientific explanation that fluids such as air and water flow from areas of high pressure to low pressure. Applications of Bernoulli’s principle include soda travelling up a sucked straw, air spewing out a newly opened coke bottle, and airplane flight. Explain how Bernoulli’s principle applies to the convection box demonstration. Bernoulli says that air flows from high to low pressure. As the hot air leaves the candle-side of the convection box, low pressure is created inside the box. According to Bernoulli, air will flow into the box to try to equalize the pressure. We could see this happening, because of the smoke.
2. Air is warmed and rises, then cools in the upper atmosphere, condenses and sinks. When cool air sinks, it displaces air at the surface and causes it to move outward and/or rise. Label the rectangle below to symbolize this cycle.