Lots of kids have combined vinegar and baking soda to make a volcano erupt. It’s a good introduction to learning about chemical reactions, but in the end you’re just left with a plaster of Paris volcano and the by-products of the experiment: sodium acetate, carbon dioxide and water. Our experiment uses the same reaction and produces the same byproducts, but our experiment is deliciously edible! We made Lava Candy. You can do this at home too- it involves cooking sugar, so adults need to stick close by and lend a hand.
We heated sugar, corn syrup and vinegar in a pot and cooked it on the stove until it reached 310°F. After removing the pan from the heat we stirred in baking powder and watched the sugar mixture foam up. We then poured the mixture onto a lined and greased cookie sheet and let the candy cool and harden. When you break the candy in pieces you reveal all of the holes created in the sugar by the carbon dioxide that was created when the vinegar and baking soda reacted.
A chemical reaction often will produce changes in color, will give off a smell or release light or gas. It often require heat or produces heat. A chemical change occurs when 2 or more things are mixed together and produce something that is different on a chemical level. Using the example of our baking soda and vinegar experiment: the chemical way of writing baking soda is NaHCo3 and vinegar is CH3COOH . When these combine, there are three biproducts: sodium acetate (CH3COONa), carbon dioxide (CO2) and water (H2O). Nothing was added or lost to the chemical equation, but on the other side of the reaction, there was no longer baking soda or vinegar. We practiced this simplified version of balancing equations by subbing in skittles for our elements: carbon, oxygen, sodium and hydrogen.
We also learned about physical reactions, best demonstrated by our Mentos and Diet Coke experiment.
The explosive eruption looks at first glance like a chemical reaction- it looks similar to the vinegar-baking soda experiment, after all. But if we think back to the earlier list of signs- is there any change in color? No. Does it create a smell? No. Does it require heat or give off heat? No. So all that’s left is: Does it give off gas or light? Definitely not light, but what about gas? The vinegar-baking soda reaction gives off carbon dioxide. The Mentos geyser is also powered by carbon dioxide, so are they actually the same? The answer is no, although carbon dioxide is the force behind both reactions. Unlike the volcano. carbon dioxide was already present in the soda before the Mentos candies were introduced. All the Mentos are doing is helping the carbon dioxide escape from the soda. The force of so much carbon dioxide escaping from the soda at the same time and such a narrow opening cause the soda to shoot up into the air. It’s a physical reaction.
Can a physical reaction be harnessed in baking? We made popovers to find out!
Popovers begin in a blender. A thin crepe-like batter is blended up and forced full of air bubbles. The batter is poured into a hot pan, where the batter begins to set immediately. The pan is placed into a hot oven where the air bubbles in the batter begin to expand and trapped inside the batter that has begun to set in the heat of the oven, it begins to expand- kind of like a balloon. If we look at our chemical change check list, there is a change in color, there is a smell, and it required the taking in of heat. So a chemical change has occurred. However, the expansion of heated air is a physical reaction. So in this experiment we observed both physical and chemical reactions.