Thursday, June 16, 2011

Kitchen Chemistry Round 2!

An Unexpected Surprise...

My daughter loves to conduct experiments. One day I walked in to my room to find three cups filled with various liquids. The first had olive oil, water, and juice. The second had olive oil, water, juice, and vinegar. The third contained olive oil and water. She wanted to know if bacteria would grow in any of the cups. I was pretty impressed by this experiment of hers, and decided to let her continue with it. After all, it's not often you have a great justification for leaving dirty dishes in your room (for the record, the juice was quick to grow mold, while the others did not).

Lately, we've been talking a lot about the digestive system. Part of this discussion has involved acids that are secreted by the liver and gall bladder in order to aid digestion. Well, this brought us right back to our acids and bases lessons from last month! We decided to conduct another kitchen experiment. This time, we wanted to test the effects of baking soda on various food items. 

Materials Needed:

Baking Soda (sodium hydrogen carbonate), cutting board, knife (with adult supervision!), paper plate, and various food items. We used tomato, watermelon, pineapple, apple, celery stalk, ketchup, mayonnaise, mustard, pickled lime, peach, Tabasco sauce, and an onion. You will want your food choices to contain a variety of foods, some acidic, others basic.


1. Using the cutting board, cut the food items into small pieces. Put the small pieces on the plate, making sure to space them far enough apart that they don't touch each other. 

This is a great time to teach lab safety procedures. Never eat anything in a chemistry lab. Protect against spills, and wash your hands thoroughly after touching your food items. 

2. Pour 2-3 Tbsp of Baking Soda onto a separate plate. 

3. Have your child assist you in putting a small pinch of baking soda on to each food item. You should start to see reactions occur on some of the food items within a few minutes.

This is a great time to talk with your child about what you have seen. Which food items showed a reaction with the baking soda? Which did not? Can you think of any reasons as to why a reaction did/did not occur? 

After we were done with this experiment, my daughter continued in the kitchen trying to see what she could discover. Because we eat a lot of spicy Mexican and Indian food, we often have Tums and Children's Pepto-Bismol on hand for tummy aches. Since the cause of the indigestion is usually an increase of stomach acid, why not see how our "tummy medicine" works to neutralize it? 

We poured vinegar into our pool test kit and tested the ph. Then we broke up an antacid tablet and added it to the vinegar. We tested the ph again to find a small increase in the ph, which meant the acidity of the vinegar was decreasing. Still, we wanted to see how it worked.

We poured about a cup of vinegar into a bowl and dropped a tablet of both Tums and Children's Pepto in at the same time. We fully expected the reactions to be the same, but what we found instead was quite surprising. We observed an immediate reaction with the Tums, while the Children's Pepto reacted slowly and in very small amounts. The carbon dioxide bubbles were present in larger numbers with the Tums than with the Children's Pepto as both tablets of calcium carbonate interacted with the acidic vinegar. 

It was interesting to see how the chemical makeup of something can affect its reaction, even when the active ingredients are the same. Even better, this proved to be a great exercise in promoting critical thinking and the skills of scientific experimentation!

Disclaimer: I am in no way affiliated with the makers of Tums of Pepto Bismol. I am simply a home school mom conducting experiments with my daughter in our home. 

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