Faraday's Candle

From the Sourcebook for Teaching Science (Herr)

Introduction

Michael Faraday (1791-1867) was a British scientist who invented the first electric motor and dynamo, demonstrated the relationship between electricity and chemical bonding, discovered Faraday's law of electrolysis, discovered electromagnetic induction (Faraday's Law), and discovered the effect of magnetism on light.  

Faraday was not only a brilliant scientist, but also a well-known educator who brought science to the public through lectures he delivered each Christmas season at the Royal Society in London.  

Faraday’s Christmas Lectures were popular because he illustrated concepts with numerous hands-on activities and experiments.  Faraday knew the importance of observation in science and began his most famous lecture series by asking his audience  to record as many observations as possible about a burning candle.  Years later, science teachers continue to use Faraday’s activity to encourage the development of observation skills.  Douglas Osheroff, the 1997 Nobel prize winner in physics (for discovery of the superfluid phases of 3H)  reflected on the importance of  this activity in his own intellectual development:  “I remember quite well one class assignment: to record our own observations of a burning candle.  I knew pretty well how a candle worked, and simply wrote down an explanation of how radiant heat from the flame melted the wax, which was then drawn up into the wick by capillary action, etc.  Mr. Hock read my explanation, and then came to me and pointed out that what I had written could not possibly have been drawn from my own observations.”  Osheroff had not made observations as requested, but had relied on his prior knowledge to explain what he was seeing.  Mr. Hock’s comments helped Osheroff distinguish observation from inference, and this distinction ultimately helped him in his career as a scientist. 

 Observations of a Candle Flame

Record all observations on the  data sheet (copy).  Place your initials in parentheses following each set of observations. (sample)

Developing Scientifically Oriented Questions (SEP-1)

In his introduction to the classic candle activity, Michael Faraday wrote: “We come here to be philosophers; and I hope you will always remember that whenever results happen, especially if it be new, you should say, 'What is the cause? Why does it occur?' and you in the course of time will find out the answer.”   Write down as many questions as you can based upon the observations you made in activity 5.2.1.   For example, “What is wax?  What is the wick?  Why is the wax soft?  Why does the wick turn black?  Why does the wax melt?  Why does the smoke ignite?  What is the substance that appears on the glass above the flame?  Why does the indicator turn color when placed over the candle?  Do all candles burn the same?...”

• • Write you own scientifically-oriented questions and submit them in the data table 

Constructing Explanations (SEP-6) 

• Explaining the phenomena  - Apply scientific ideas, principles, and evidence to provide an explanation for each of the following phenomena 

• Scientific Principles - On "scientific principles" tab, describe how the observations from this activity can lead into discussions of scientific principles

• Environmental Issues - On the "environmental issues" tab discuss how combustion is related to various environmental issues.

Arguing from Evidence (SEP-7)

• As a class, discuss the explanations.  Each student should argue from evidence.

• Energy Balance Calculations

NGSS-based  3-course Model

• Chemistry in the Earth System