Dancing Popcorn

Introduction:

Making good observations are a key to solving scientific problems. Being a good observer means that you watch events closely and try to experience them with as many senses as possible. In this activity, your job is to carefully observe the behavior of the popcorn in a carbonated drink and then develop an explanation (hypothesis) that can be used to explain your observations.

Materials: 

Teacher Led Exploration:

Begin this exploration by giving each group of students a cup of Sprite or 7-up and 5-6 popcorn kernels. Have the students place the popcorn into the cup and observe the behavior of the kernels. Raisins also work instead of popcorn but they should be soaked in water for an hour prior to the activity. 

Now ask students to develop ideas to explain what is happening to the popcorn. Encourage them to think of as many ideas as possible and let them discuss their ideas in small groups for a minute or two.  Then discuss these ideas as a group encouraging them to be creative and "out of the box" in their thinking. 

 Guiding Questions:  

1.  Besides watching the popcorn, what other senses did you use to help you make observations?

2.  Explain what do you think is causing the popcorn kernels to sink and float.

3.  Why are some of the kernels floating and others are not?

4.  Try to think of one other example that demonstrates this same idea. 

5.  If you were lost in a lake or the ocean and had to stay afloat for a long time, how do you think you could create some bubbles to make you float like the popcorn did?

Explanation:

Objectives Covered:

QCC # 1. 1 - 5.1    Science Inquiry, Process Skills, and Problem Solving

The student will ask questions, make and keep simple records of observations, sort and classify objects, communicate with others, make predictions, use estimation and measurement, and make sketches and diagrams to explain ideas.

Concept Discussion:  

Initially, the kernels are more dense (heavier per unit)) than the drink and so they sink to the bottom. But carbonated drinks contain carbon dioxide gas bubbles and these bubbles tend to collect on the popcorn.  As they do, the kernel and bubbles together become less dense (lighter per unit) than the liquid around it and so they float to the top. Once they reach the top, the bubbles escape into the air and the popcorn by itself again sink to the bottom.  

Density is a difficult concept for younger children to understand but  ideas of heaviness and lightness are more easily understood.  By gaining bubbles, the kernels improve their buoyancy thus gaining the ability to float. Fish can regulate how well they float or sink in the water by controlling the amount of air they keep in their swim bladders. Sailors who are lost at sea can improve their chances at surviving by blowing up their pants to make two big bubbles in the legs. Their buoyancy improves and they are able to stay afloat for longer periods of time.