This activity is another use of your Halloween candy stash. It is adapted from an activity on CandyExperiments.com - which is a very fun site you should definitely check out for more ideas of what to do with your leftover candy.
Many types of candy has an acid as one of its major ingredients (the origin of the sour flavor) and it will react with baking soda to form bubbles of carbon dioxide. Since we've been talking lately at the dinner table about the importance of chewing your food rather than swallowing it whole, this activity also looks at the impact of surface area on the reaction that is created.
- a couple of rolls of Smarties candy (the sour sugar candy not the chocolate wafers)
- water (and a pitcher if you are adventurous and want to let your child practice pouring)
- 2 clear cups
- baking soda
- 1 teaspoon
- wooden or rubber mallet
- sandwich-size plastic bags
You could do this with only one roll, but its nice to have an extra so you can use the same color Smarty (singular of Smarties?) for the different parts of the experiment. Controlling variables and all. Other sour-tasting candies (like SweeTarts) can be substituted here, although for the second part of the experiment it really should be able to be crumbled or smashed. (I'm partial to Smarties, anyway. I used to eat them, and Nerds, before tests in high school to ostensibly give me some brain-boosting power. I know, I know - what a geek!)
Process and Pictures:
Part I: The Importance of Baking Soda
Start off by showing your child the Smarties candy and telling them that you are going to add the candy to some different liquids to see what happens to it.
Have them pour about 1/2 cup of water into each of the two cups. (You can label the cups and draw a line on them to help, which I did although you can't really see it from the picture to the right.)
Then, measure 1 teaspoon of baking soda and add that to one of the cups. Have your child stir the baking soda into the water and then let it settle for a bit. (This part is important because when you first add the baking soda, the solution is pretty cloudy and you want it to clear up so that you can see the bubbles better.)
Give your child two Smarties (preferably the same color) and have them drop the Smarties into the cups at the same time. We did a count-down and its not really that important that they go at the exact same time, just as long as its pretty close.
Observe what happens in each of the cups. They should be able to see the bubbles coming off the candy that is in the baking soda solution. If you lift the cup to their ear they should be able to hear it as well. This might be a good time to review the five senses with them (touch, taste, smell, hearing, and sight) - and also remind them not to taste this experiment. (In small amounts it wouldn't hurt them at all, but I don't think it would taste especially good.)
If you are using a science journal or something similar, have them record their observations in it before moving on. Discard the solution and rinse out the cups because they are going to be used again in the next step.
Part II: Smashed v. Whole Smarties
Now that you've established that Smarties react with a baking soda solution to form bubbles of carbon dioxide, we are going to experiment with how the size of the Smarties affects the reaction.
Again, add about 1/2 cup of water to each of the cups. Then, add 1 teaspoon of baking soda to each of the cups and have them stir it in. Let the solution settle for a bit so that it clears up.
For this part of the experiment, each child needs 4 Smarties. Put two of the Smarties aside and then take the other two and place them in a sandwich-size plastic baggie. (Make sure the top is well secured!) Let them pound the candies into very small pieces.
At this point, pause and ask your child to predict which type of Smarties, the smashed one or the whole one, they think will make more bubbles when it is added to the baking soda water.
You are going to add the Smarties to the two cups of baking soda water simultaneously, or as close as you can get it. We found that it was a little tough to get the Smarties powder out of the plastic bag as it kept getting stuck in the zipper at the top. Instead, we snipped a hole in one of the bottom corners and I poured it out of the hole into one of the cups while the girls dropped the whole Smarties into the other cup.
Observe the reactions that occur in the two cups. They should be able to see a great deal more bubbles in the cup with the smashed up Smarties. Again, lift up the cup to their ear and have them listen to the difference in the bubbles - I think its much more extreme than just looking at it.
Revisit their prediction about whether the whole or smashed up Smarties would make the greater number of bubbles. If you are using some sort of science journal, give them time to record their thoughts and observations. Sydney's journal is pictured to the right and, as you can see, its a combination of her drawing and both of our lettering. I try to have her write a summary sentence after each activity (which you can kind of see at the bottom) but I help her with some of the other writing. Also, as a note, I didn't think Maya, who is 3, was getting anything out of the journal process, but she opened to the graph that we did last week and she said, "Look, Momma, that's from our M&Ms", so maybe she is getting more out of it than I thought!
Smarties candy contains an acid known as citric acid (the same one that is in citrus fruits) that is responsible for its sour taste. Citric acid will react with the baking soda (sodium bicarbonate) solution to form bubbles of carbon dioxide. Sodium bicarbonate is actually a weak base and it breaks apart in water; it is then free to react with the citric acid and forms not only carbon dioxide but also sodium citrate and water, although these aren't as readily apparent in our experiment.
This activity also examines the affect of surface area on the rate of a chemical reaction. As predicted by my girls, the smaller pieces/greater surface area had a much faster reaction rate/greater bubbles than the whole pieces of Smarties. I tied this idea into why its important to chew your food when you eat rather than just swallowing it whole. When you chew your food well, then the smaller pieces make it easier for your stomach to break it down the rest of the way so that you can get energy out of the food.
You could use this basic technique as an acid test and drop a variety of candy types into the baking soda solution to determine whether or not they have acid in them. A great way to use up a huge quantity of candy in a short amount of time!
Another thing you could do is use it to experiment with other things that might affect the reaction rate, i.e. temperature or quantity of solution. Fill one cup with hot water and one cup with cold water and drop a whole Smarties candy into each one and see if you can discern any difference in the reaction rates. Or, fill one cup with a tiny amount of solution and fill the other to the brim and make the same observations.
For older kids, the reaction of sodium chloride and water is actually an endothermic reaction, meaning that it absorbs energy from its surroundings thereby making the solution itself cooler. Use a thermometer to see if you can measure the decrease in temperature that occurs when you mix the two substances together. You may need to use an insulated cup and play a bit with quantities to get a discernible difference (depending on the sensitivity of your thermometer) but, hey, that's part of the fun!