One thing I love about doing science with kids is that, regardless of their age, they can participate and enjoy it at some level. This is a perfect example. Even younger children will have fun putting apple slices into cups and watching what happens. Older children can make hypothesis (educated guesses) about what will happen and try to draw conclusions about what happened. I’ll do my best to make it simple to do and easy to understand!
Apples turn brown when they’re cut open and exposed to air. This is the result of oxygen in the air reacting with enzymes and other chemical compounds in the apples. We’re going to observe what happens when you treat apple slices with acids (lemon juice and vinegar) and a base (baking soda and water). We will also watch how fast treated apple slices turn brown compared to an untreated apple slice!
You could ask your child to choose one of the following hypothesis: 1. A solution with acid in it will stop the apples from turning brown so fast. or 2. A solution with acid in it will not change how fast the apples turn brown. Older kids could write their hypothesis in their notebooks!
Materials: an apple, vinegar (white or apple cider), lemon juice, baking soda, water, five clear containers (plastic cups or glasses) labeled as follows: no treatment, water, baking soda, lemon juice, vinegar.
Mix together about 1/2 tsp of baking soda in 1/4 cup water. Add it to the appropriate container. To another container, add 1/4 cup vinegar, to another add 1/4 cup water and to another add 1/4 cup lemon juice. Leave one cup empty for your “no treatment” apple, or the one just exposed to air. Your child can help you do this! Make sure small children don’t rub or splash vinegar or lemon juice in their eyes. Remember, they’re acids! Explain to them that lemon juice and vinager are acids and baking soda makes a basic solution. Water is pretty neutral (neither an acid or a base.) If they want to know more about acids and bases, go to http://library.thinkquest.org/J001539/
Slice the apple and immediately have your child add a slice to each cup, thoroughly coating the apple slices with solution. Pour the solutions out, leaving the apple slices in the cups. Help your child write down or draw how the slices look. They can make a table in their lab notebook to record their observations, with treatment in one column next to appearance in the next column (save room for more columns to note appearance over time.) I had to cover our cups loosely with foil due to the frightening number of fruit flies that have recently invaded my kitchen.
Have them observe the slices in a few hours and over the next few days, recording their observations if they want to . They may want to draw how the slices look over time, or even take pictures for their science notebooks.
Finally, have them draw a conclusion from their observations (data) and record it in their notebook if they want to. Did the solutions keep the apples from turning brown? Was their hypothesis correct? Which solutions worked best? Did both acids (lemon juice and vinegar) help preserve the color? If not, does this suggest that it was something else in the solution, and not just the acid that preserved the color? What did the water do? The base?
You can make it as simple or complicated as you want to! Just make it fun and don’t take over. Let your kids get their hands dirty!