Rocket opens the fridge and starts pointing. "Lemons, acid. Oranges, acid. Vinegar, acid." He opens a cabinet. "Baking soda, base."
Raven leans against the counter with the Bench Log. "What do you notice about the sink?" she asks. "The dish soap is a base too."
"Everything is one or the other," Rocket says.
"Or neutral," Raven says. "Water."
Nova hovers near a locked cabinet under the sink. "And what about in there?" she asks. "What is the rule?"
Rocket does not even look. "Cleaners stay out of the Bench. Ammonia is a base. Drain cleaner is a base. Neither is a kitchen base."
Raven writes the rule in capital letters: KITCHEN ONLY. Then she adds, "and never mix two cleaners."
Your own stomach uses hydrochloric acid to digest food. An antacid is a base that reacts with that acid and neutralizes it.
Vinegar, which is dilute acetic acid, can dissolve the lime deposits that build up inside a coffee maker.
Soaps are bases, and so is baking soda. Both feel slippery in water.
Many cleaners contain ammonia, a base. Sodium hydroxide is found in drain cleaner. These are strong, and they never come to the Bench.
Now you can explain week 7. Vinegar is an acid. Baking soda, sodium hydrogen carbonate, is a base.
Acids react with bases. In this reaction, carbon dioxide gas is one of the products, and that gas is the fizz.
Lemon juice fizzed too, because citric acid is also an acid. Would soap water fizz with baking soda? Both are bases, so there is no acid to react.
| Everyday item | Acid or base? | How you know |
|---|---|---|
| Lemon juice | Acid | Contains citric acid; turns cabbage juice red |
| Vinegar | Acid | Contains acetic acid; turns cabbage juice red |
| Baking soda | Base | Sodium hydrogen carbonate; turns cabbage juice green |
| Dish soap | Base | Slippery; turns cabbage juice green |
| Pure water | Neutral | pH 7; cabbage juice stays purple |
| Ammonia cleaner | Base | Named in the chemistry text; never used at the Bench |
| Week review | True or false? |
|---|---|
| Vinegar contains acetic acid and lemons contain citric acid. | ? |
| Soaps and baking soda are bases. | ? |
| A pH above 7 is acidic. | ? |
| Red cabbage dye turns red in an acid and green in a base. | ? |
| Ammonia cleaner is a safe kitchen base for the Bench. | ? |
When you poured vinegar on baking soda, did the cup feel cooler? Some reactions take in energy, and some give it out.
Next week you will measure that temperature change with a thermometer and find out which way it goes.
Strong week, Bench chemist. Tomorrow is Bench Day: a family cabbage rainbow.