I light the candles for the students in this age group (6th)
Discuss how candles work and the fire triangle (link)
Discuss combustion and the chemical reactions that takes place when a candle burns
Explain the lab procedures and remind students of safety protocols
Students will record qualitative and quantitative observations of an unlit candle (5 minutes), burning candle (10 minutes), and a covered burning candle until it goes out and the wax hardens (5 minutes)
all students will place the larger beaker over the candle at the same time and watch as the candle goes out
Share observations and discuss
I like to use this lab as part of my physical and chemical changes unit, it is such a classic and the kids make some great observations and ask lots of good questions.
Optional – privacy screen made of one manila folder cut in half and stapled together
View my Properties of Matter resources for related lessons (page)
This is a fun partner activity that I use as part of my Chemistry unit to get students thinking about the differences between physical and chemical changes. Each pair of students is given a set of cards with images and descriptions of either a physical change or a chemical change. (see photo above)
Each pair goes through the cards and discusses/decides where the each card will be placed. Once they have categorized the cards, students call me over verify their work – I will either say “Yes, they are all in the correct category!” or “Not quite yet, try again.” I give a small clue each time I come over. For example, I will say something along the lines of “You have 2 in the incorrect column” or “You have too many in the Physical Change category, which ones should be moved to the Chemical Change category?” or “Two cards need to be flip/flopped to the other category, all the other cards have been placed correctly” or “All of the cards that are placed in the Chemical Change group belong there, but not all of them are there quite yet, what else can you move to that category?” – I won’t tell them the specifics of what needs to be changed. This forces the students to re-evaluate their choices and make changes as needed until all of their cards in the correct category.
Every few minutes, I will give the whole class a clue. This allows them to check their progress and verify one answer at a time. One card that many students have difficulty with is the boiling water card – and that is usually the first clue I will give out once I have had a chance to check every group’s progress. Each pair of students continues working together until all the cards are placed in the correct category. Once I’ve verified their placements, they add the answers to their notes and answer the questions for the activity and we discuss our results.