What’s the Solution?
Seeing liquids change colors is one of the most fascinating and immediately gratifying things that a young pupil can see and observe. In this fun experiment, the kids will get to see vibrant colors change before their very eyes. The chemistry concepts here are simple: a chemical reaction is occurring. A chemical reaction is when one substance changes to become another. Color change is evidence of a chemical reaction, but so is heat, fizz (release of gas), precipitates (solids forming out of liquids is an example of a precipitate), change of odor.
The science behind chemical reactions can get pretty intense, but for elementary kids, it is fun just to let them play around with safe ingredients that when combined, have plenty of wow factor.
Concepts: In this lab, the kids will learn if something is an acid, a base or neutral.
Safety: Adults should cut the cabbage and use the blender. Kids can help by adding the water to the blender. Kids should be wearing chemical goggles when conducting this lab to protect their eyes from irritants such as the vinegar. Lab coats should also be worn, as cabbage juice will stain clothing.
What’s Going to Happen: Red cabbage juice is known as an acid/base indicator because it changes colors if it is exposed to an acid or a base. Cabbage juice is naturally neutral and it has a purplish color. If an acid is added, it turns blue or greenish. Vinegar makes the juice turn into a reddish color, so it is an acid. Baking-soda makes the cabbage juice turn into a blur or greenish color, so it is a base.
1 cup of chopped-up red cabbage
1 cup of water
3 tablespoons of vinegar
3 tablespoons of baking soda
a piece of cheesecloth folded over for a strainer
a large wide-mouth container for the cabbage water
knife for chopping cabbage
1 straw cut into half to make two stirring rods
two plastic cups for each child
1. Chop up 250 mL of red cabbage (about 1/4 of a cabbage).
2. Make cabbage juice by adding the chopped-up cabbage into a blender. Add a cup of water and blend until the water turns a dark purple color.
3. Make a strainer by folding cheesecloth in half and setting it in a wide-mouthed container. Slowly pour the cabbage slurry into the cheesecloth. Save the liquid and discard the solids. Add about 125 mL (about 1/2 cup) of cabbage juice to each cup.
4. Add 15 mL (three tablespoons) of vinegar to one container of cabbage juice and watch what happens.
5. To the other container, add 15 mL (three tablespoons) of baking soda and watch what happens.
There are a lot of spin-off activities you can do with simple cabbage water. Keep some in the fridge in a sealed bottle or container and it’ll keep a few weeks, and you can take it out whenever the kids want to experiment with it.
Use other household ingredients to see if they’re an acid or a base. Dish soap (base), lemon or lime juice (acid), toothpaste (base), egg whites (base). Get creative! Just be careful that you don’t let the kids mix any household cleaners or chemicals.