OK, so I have to admit the ACS Middleschool science curriculum is really starting to bore me. The labs we were to do this week basically involved watching wet paper towels dry (evaporation)…. um, no thanks. So we watched candles burn instead. I did talk about evaporation and condensation (something that doesn’t happen in dry California that much) but we left it at that.
The lab we did do comes from Middleschoolscience.com and is called the Candle Observation Lab and she has a link on there to the NakedScientist lab called Getting Water from a Candle. The NakedScientist website has an audio recording about the experiment that you can listen to as well as a short clip of placing a glass over a candle.
This lab mainly consisted of writing down observations, first before the candle was lit (describe the wax, the wick, does it smell? Color? Texture? Used or unused? and drawing the candle. Then I lit the candles and they observed them over 10 minutes, again making a drawing and describing the flame, melting wax etc. After putting a glass beaker over the candles they once again described what they saw and made a drawing… or a series of drawings. The students weren’t sure if the beakers would actually extinguish the flames since they didn’t form a perfect seal with the plates but the flames indeed got smaller and went out pretty quickly as smoke filled the beaker and water vapor condensed on the glass.
The students knew the fire needed oxygen but they thought that the oxygen was the fuel, so I explained how as the wax melts it gets sucked up into the wick and becomes the fuel for the fire, which is why the amount of wax left in your candle decreases til there is nothing left if you leave it burning long enough.
I provided a handout for their notebooks with the images from the NakedScientist like the one on the left showing the chemicals being used up and produced by the fire.
We also used a page from an interactive notebook bundle I got from TeachersPayTeachers. Combustion is from the Chemistry Interactive Notebook by Stephanie Elkowitz. Its a nice simple flap where the students put the necessary ingredients for combustion on the left and the products on the right.This really helped since it has Oxygen and Fuel on the left, which most students thought was the same thing, but when I asked what is used as fuel for a campfire they knew it was the wood. Under the flap we listed some different fuels and the fact that combustion is an exothermic reactions (gives off heat/energy).
We had 30 minutes left so we did an activity on physical changes versus chemical changes.
Each pair of students were given a set of cards and asked to separate them into two piles, the cards that demonstrated a physcial change (like boiling water – its still water, its just in a different physical form) and the cards that showed a chemical change (like baking a cake). Once they had the cards sorted correctly, which took a few trys, they wrote down the answers on a form for their books. Some of the students decided to paste the cards into their books which was a great idea. I got this activity from Stephanie Elkowitz’s Chemistry Interactive Notebooks as well.
We showed a few videos in class, 2 having to do with how Astronauts can make water in space (or on Mars, like Mark Watney in the Martian…. I love that book!)
And this video on how to make water with combustion.
And lastly, I asked the students why is the candle flame that particular shape? And what would it look like on the space station?