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Explore how fizzing and bubbling indicate that a new gas is being created.
Have you ever wondered why a cake rises in the oven or why a 'science volcano' erupts so suddenly? It is all thanks to invisible gases making a very noisy, bubbly entrance!
In chemistry, a chemical change happens when substances bump into each other and trade parts to create something entirely new. Unlike a physical change (like freezing water into ice), you can't easily turn a chemical change back! One of the most exciting ways to spot a chemical change is gas production. When a new gas is formed, it often gets trapped in the liquid, creating the fizzing or bubbling we see. These bubbles are not just air; they are a brand-new substance that wasn't there before the reaction started.
Quick Check
If you see bubbles forming when two room-temperature liquids are mixed, what does this likely indicate?
Answer
It indicates that a chemical change is occurring and a new gas is being produced.
You can actually 'see' the gas being made by trapping it! 1. Pour a small amount of vinegar into a plastic bottle. 2. Use a funnel to put a spoonful of baking soda inside a balloon. 3. Stretch the balloon over the mouth of the bottle without dropping the powder in yet. 4. Lift the balloon so the baking soda falls into the vinegar. 5. Watch as the gas fills and inflates the balloon!
Quick Check
What is the specific gas produced when vinegar and baking soda are mixed?
Answer
Carbon dioxide ().
It is easy to get confused: both boiling water and chemical reactions make bubbles. However, they are very different! When you boil water, you are adding heat to turn liquid into water vapor ( gas). This is a physical change because it is still just water. In a chemical reaction, the bubbles are a different substance than the liquid. For example, when you drop an antacid tablet in water, the bubbles are carbon dioxide, not 'water gas.' If bubbles appear without you adding heat, it is a huge clue that a chemical change is happening.
Imagine you have two pots of clear liquid. 1. Pot A is on a hot stove and starts bubbling at . 2. Pot B is sitting on a cold counter. You drop a white powder into it, and it immediately starts fizzing. 3. Pot A is undergoing a physical change (boiling). 4. Pot B is undergoing a chemical change (gas production) because the bubbles appeared due to a reaction, not heat.
If you measure the mass of vinegar and baking soda separately as total, then mix them in an open bowl, the final mass might only be . Where did the go? 1. The 'missing' mass is the gas that floated away into the air. 2. To prove the Law of Conservation of Mass, you would need to perform the reaction in a sealed container so the gas cannot escape. 3. In a sealed system, the mass before () would equal the mass after ().
Which of the following is a sign of a chemical change?
In the equation , which part represents the bubbles?
Bubbles in boiling water are a sign of a chemical change.
Review Tomorrow
Tomorrow, try to explain to a friend why a 'vinegar volcano' eventually stops fizzing. What happened to the ingredients?
Practice Activity
Look in your kitchen (with an adult) for 'Alka-Seltzer' or baking powder. Drop a small amount in water and observe the gas production. Is the water getting hotter, or is it a chemical reaction?