Of the three states of matter, many people think that solids and liquids are the only two to worry about in the kitchen, but this month we’ll play around with gases and show that they’re just as essential! You will need some very basic things that are likely already in your house: yeast, sugar, vinegar, baking soda, water and a couple of clean bottles and balloons. Any kind of bottle is fine, and somewhere in the 375 mL to 500 mL range is best.
When we make foods that are leavened, we are taking a liquid or solid (batter, dough, etc.) and introducing carbon dioxide gas: in other words, we’re filling it with bubbles. Different recipes use different leavening agents (yeast, vinegar and baking soda, and baking powder are all very common agents), but they all have the effect of producing bubbles of CO2 gas that get trapped inside of our food. It’s the same stuff we breathe out, and it’s easy to demonstrate.
To show how the two most common leavening agents work (yeast and baking soda/vinegar), we’ll mix them up and trap them in bottles to see the gas being produced. Simply mix one cup of warm water (below 50°C or 120°F) with 2 tablespoons of sugar with one package (45 mL or 2 1/4 teaspoons) of yeast in your clean pop bottle. Fit the top with a balloon and wait. The same can be done with baking soda and vinegar, but because the reaction happens much faster, you’ll want to put baking soda in the bottle and vinegar in the balloon so that the balloon can be sealed onto your bottle before you mix the two (just lift the balloon up to dump the vinegar in).
Both balloons will end up inflated, showing just how much gas can be produced by pretty small amounts of material. The yeast breathes out CO2 (just like us!) as it eats the sugar, and baking soda and vinegar react chemically to produce the CO2. Either way, you’re making gas in your container, which ably demonstrates how baked goods get fluffier!
If this gives you an appetite for more live science, check out our live demonstrations on daily at the Discovery Centre!