Just Enough Vinegar
- Chemistry
- Ages 8–11 · Grades 3–5
- Hands-on experiment
What you’ll find out
- The amount of product depends on the amounts of the starting materials.
- When one ingredient runs out, the reaction stops, however much of the other is left.
- Measuring carefully makes results fair and repeatable.
No sign-up and no real names. In the lesson you check your understanding as you read, run the experiment yourself, and practise until it sticks.
More baking soda, more gas
Vinegar and baking soda react to make a gas called carbon dioxide. That is the fizz. You can catch the gas in a balloon. Put vinegar in a bottle. Put baking soda in a balloon. Stretch the balloon over the bottle and tip the powder in. It fizzes and the balloon blows up! Now measure. Use the same half cup of vinegar each time. Change only the baking soda. One teaspoon makes a small balloon. Two teaspoons make about twice as much gas.
When one runs out
But if you keep adding baking soda, something odd happens. Half a cup of vinegar can only use about two teaspoons of baking soda. Put in four teaspoons, and the balloon is no bigger than with two. White powder is left at the bottom! The vinegar has run out, so the fizzing stops. To make more gas now, you need more vinegar, not more powder. A whole cup of vinegar with four teaspoons makes twice as much gas. Recipes are like this too. If you run out of eggs, you cannot make more cakes, however much flour you have.
Curriculum links: NGSS 5-PS1-4 · NGSS 5-PS1-2