"Vomiting" Pumpkins

This activity of "vomiting" pumpkins I first saw on Pinterest as "erupting" pumpkin.  We had already done erupting volcanoes last school year, and vomiting pumpkin just sounds so groos AND cool! It requires the two basic ingredients: baking soda (sodium bicarbonate-NaHCo3), vinegar (CH3COOH), and food coloring. We used 4 colors. They love to "see" things happen, I therefore decided this would be perfect activity for my classroom.

Before we made our pumpkins vomit, I formed 5 groups of four. They began the activity by measuring the circumference, figuring out the diameter, and the radius to the nearest inch and centimeter. They then had to give me an approximate weight for their pumpkin using a nonstandard unit. We decided to use our health books as the tool. (Excellent way to review math concepts from earlier years!)

They decided on a particular face, and my parent volunteer and I cut out the faces for them. They had to remove all the insides...yucky according to many, but they had a blast. They counted their seeds (which we will use later on as a way to review mean, median, range, outlier, etc.)

 

As a way to connect it to their "schema"-they LOVE that word--, we discussed how we had made our volcanoes erupt last year. This year we have been talking a lot about chemical reactions, so we decided to figure out what happens and why. We looked up the chemical formula for each reactant and did some research. We discovered that the reason vinegar and baking soda react is actually the result of two separate, but continuous reactions. The simple version is: the baking soda dissolves in the water, then reacts with the aceitic acid, which quickly reacts, to form carbon dioxide escaping from the solution as a gas--that is the bubbles/fizzing you "see".

NahCO3 + CH3COOH = H2O + Sodium acetate (CH₃COONa) + C02

They  were amazed to find out that what we breathe out is what was causing the fizzing.

Here we are outside setting up the experiment. We measured out about 5 spoonfuls to 1/2 a cup of vinegar. We repeated the experiment with 3/4 cup of baking soda to 1 cup of vinegar--lots more fizzing.
 

 

 The faces with a larger mouth closer to the base of the pumpkin had the most "vomit" coming out.

My intent is not to teach them chemical formulas, BUT to excite them and get them very interested in science, and above all to have them asking a ton of questions =)

What other Halloween activities do you do to get your kiddos excited about learning?