Recently, my class had been studying physical and chemical changes. We also did two labs to go along with the lesson. One was called Observing a Candle, and the other was called Pouring a Gas. For the first lab, each group had a yellow candle with white stripes, and it was standing on the table by having a piece of yellow clay molded around it. First, we had to prepare a data table that would list the physical properties and chemical properties of a lit and unlit candle. After that, we had to observe the unlit candle and write down all of it's properties. Later, our teacher came around to each lab and lit the candle so we could record our observations for it. For the second lab, each group had a beaker full of vinegar and another beaker filled with baking soda. Carefully, we had to add a small amount of baking soda to the vinegar. This procedure caused the liquid to fizz, which was a chemical reaction. However, it did not overflow. Following the directions for the Pouring a Gas lab, one person in my group tilted the beaker with both components over the lit candle and the flame went out. A potent smell of waxy smoke filled our noses, almost like when someone makes a wish and blows out their birthday candles. Doing these labs also helped me further my knowledge on physical and chemical changes of a substance.
One interesting fact that I learned was that when you add carbon dioxide to a flame, it extinguishes immediately. Another fact I learned was that a physical change changes the form of a substance while a chemical change changes the entire substance. I also found out that the name of the process of burning a candle is called combustion. However, I also learned more about this from further research. For example, the website I explored said this is an exothermic change, due to the fact that it releases heat to the atmosphere along with other products. Lastly, this website also informed me that the concentration of oxygen is greatest on the outer edge of the flame since the source of the oxygen is the atmosphere.
In my opinion, this lab was an excellent way to learn about chemical and physical changes through a hands-on activity. This way, we could process more information through doing the lab, instead of sitting and taking notes. Plus, the fact that burning a candle is an example of chemical change, it was fun to actually do it with fellow classmates and learn together. I enjoyed learning that mixing baking soda and vinegar could extinguish a fire because it was unique to see a fire put out without the use of water or a fire blanket. I always think it is extremely fun to do an activity where you can follow the steps and get a really cool result. Such as, starting out with baking soda and vinegar in separate beakers and an unlit candle. Then, as we followed the steps, we extended our knowledge of physical and chemical changes, finally learning that a candle has flammability and can be put out with simple household components, due to the carbon dioxide. Overall, this lab was a phenomenal way to continue the lesson of physical and chemical changes and I would love to do ones like this in the future.
My Further Information: http://www.newton.dep.anl.gov/askasci/chem99/chem99454.htm
