Monday, 13 February 2017

Chemical History of a Candle: bonus experiment

We are reading Michael Faraday's Six Lectures for the chemistry component of a Year 9 science class. As you can surmise from the title of the book, there is a lot of candle burning going on.

The experiments involve close observation of the flame and usually involves its going out in different situations using up many matches in the process of relighting the candle often.  One student casually wondered how matches work so I assigned that question as homework.

When we reconvened the following week, the students' narrations then led to wondering if all matches were the same? So we decided to find out and set up an experiment using different kinds of matches.

Surprisingly, I had 8 different types of matches on hand: ones with turquoise match heads, black, white or pink match heads, red with white tips of various sizes and matches with cardboard sticks from souvenir matchbooks.  We used the same igniter for each strike to keep that consistent.

The students decided what they could observe that might distinguish matches from each other: What does it smell like when it first burns? or when it is first put out? What colour is the flame and the smoke? How big is the flame?

One thing usually leads to another and investigations usually lead to more questions.  They wondered if the different colours were just a dye on top of the usually red phosphorus match head or its true colour.  They first put it under a microscope to examine the match head and then started scraping off layers of the colour to see how it was constructed.